Guillaume Billet

Stéphane Peigné

Maeva Damien Germain

Miguel Garcia Sanz

Florent Goussard

Patricia Wils

Gaël Clément

Aurélie Lesur

Marc Verguin

Eric Herbin

Jacques Pellé

Cuisin

Pip Brewer

Dan Sykes

Farah Ahmed

Judith Galkin

Henry Tobin

Alana Gishlick

Ruth O'leary

Morgan Hill

Jin Meng

Du

Julien Benoit

Rodolphe Tabuce

Renaud Lebrun

les collections de paléontologie du Muséum, Joséphine

Keywords: petrosal, labyrinth, Proboscidea, elephant, anatomy, phylogeny, functional analysis

On pourrait penser qu'une thèse est un travail solitaire. Loin de là. Bien qu'il s'agisse d'un travail personnel qui nécessite d'être autonome, les trois ans passés à préparer ce diplôme m'ont donné l'opportunité d'échanger avec de nombreuses personnes. Personnes qui ont participé à faire de cette thèse ce qu'elle est aujourd'hui et que j'aimerais remercier.

Je tiens avant tout à remercier mes directeurs de thèse, au nombre de deux (ou trois) pour leur disponibilité et leur engagement et qui m'ont accompagné durablement tout au long de ce travail « mastodontesque » que peut représenter une thèse de doctorat.

A Emmanuel Gheerbrant, qui a le courage de m'encadrer depuis presque 5 ans déjà puisqu'il supervise mon travail depuis ma première année de Master.

A Pascal Tassy, véritable encyclopédie vivante des proboscidiens et qui a su toujours rester disponible malgré la distance.

A Romain David, qui n'est pas officiellement un directeur de cette thèse, mais qui s'est investi dans ce travail tout autant que les précédents, en me faisant découvrir le monde (magique) de la biomécanique des canaux semi-circulaires.

Je remercie également les autres personnes qui ont pu contribuer à améliorer ce travail. La recherche est une activité qui peut s'avérer bien solitaire, mais partager et échanger avec d'autres collègues est primordial pour faire mûrir un projet de recherche. Pour ces raisons, je tiens à

 [START_REF] Gheerbrant | L'origine et l'évolution des éléphants[END_REF]. The earliest-known proboscidean, Eritherium azzouzorum Gheerbrant, 2009 (Selandian, 60 Ma) has the size of a large hyrax and retains numerous paenungulate plesiomorphies [START_REF] Gheerbrant | Paleocene emergence of elephant relatives and the rapid radiation of African ungulates[END_REF]. It was discovered in the Ouled Abdoun basin in Morocco that also yielded the more recent Phosphatherium escuilliei Gheerbrant, Sudre & Cappetta, 1996 (Ypresian, 55 Ma) which is slightly larger and more derived than Eritherium [START_REF] Gheerbrant | A Paleocene proboscidean from Morocco[END_REF][START_REF] Gheerbrant | Phosphatherium escuilliei du Thanétien du bassin des Ouled Abdoun (Maroc), plus ancien proboscidien (Mammalia) d'Afrique[END_REF][START_REF] Gheerbrant | Nouvelles données sur Phosphatherium escuilliei (Mammalia, Proboscidea) de l'Eocène inférieur du Maroc, apports à la phylogénie des Proboscidea et des ongulés lophodontes[END_REF], and Daouitherium rebouli [START_REF] Gheerbrant | A new large mammal from the Ypresian of Morocco: Evidence of a surprising diversity of early proboscideans[END_REF](Middle Introduction Jaeger, 1986(described in Mahboubi et al. 1986) from the midlle Eocene of El Kohol, Algeria; Barytherium grave [START_REF] Andrews | Über das Vorkommen von Proboscidiern in untertertiären Ablagerungen Aegypten[END_REF] from the late Eocene and early Oligocene of the Fayum [START_REF] Andrews | Über das Vorkommen von Proboscidiern in untertertiären Ablagerungen Aegypten[END_REF][START_REF] Andrews | A descriptive catalogue of the Tertiary Vertebrata of the Fayûm, Egypt. British Museum (Natural History[END_REF], Egypt, and of Dor El Talah, Libya; and

Arcanotherium savagei [START_REF] Court | A new species of Numidotherium (Mammalia : Proboscidea) from the Eocene of Libya and the early phylogeny of the Proboscidea[END_REF] from the late Eocene and early Oligocene of Dor El Talah [START_REF] Court | A new species of Numidotherium (Mammalia : Proboscidea) from the Eocene of Libya and the early phylogeny of the Proboscidea[END_REF][START_REF] Delmer | Reassessment of the generic attribution of Numidotherium savagei and the homologies of lower incisors in proboscideans[END_REF], Libya.

Moeritherium from the Eocene of North Africa, and peculiarly from the late Eocene to early Oligocene of the Fayum and Dor El Tahla [START_REF] Andrews | Über das Vorkommen von Proboscidiern in untertertiären Ablagerungen Aegypten[END_REF][START_REF] Tassy | Le crâne de Moeritherium (Proboscidea, Mammalia) de l'Eocène de Dor El Talha (Libye) et le problème de la classification phylogénétique du genre dans les Tethytheria McKenna[END_REF], is more closely related to modern elephants than previously cited proboscideans. Indeed, it is the earliest known proboscidean with bunolophodont molars and with an undivided perilymphatic foramen [START_REF] Gheerbrant | L'origine et l'évolution des éléphants[END_REF]. inferior tusks [START_REF] Gheerbrant | L'origine et l'évolution des éléphants[END_REF].

Table 1 : Simplified classification of the main proboscidean groups and taxa presented in the introduction, after [START_REF] Gheerbrant | L'origine et l'évolution des éléphants[END_REF]. '?' is for debated attributions. Not all proboscidean taxa are represented here.

Introduction

The Elephantiformes is a vast clade that contains all proboscideans that display the modern elephantine graviportal posture. The group originates in the early Oligocene of North Africa from genera like Palaeomastodon [START_REF] Andrews | Über das Vorkommen von Proboscidiern in untertertiären Ablagerungen Aegypten[END_REF]Phiomia Andrews &[START_REF] Andrews | A preliminary note on some new mammals from the Upper Eocene of Egypt[END_REF] that were discovered initially in the Fayum Jebel Qatrani Formation.

Within the Elephantiformes, a major radiation occurs in the Neogene:

the Elephantimorpha Tassy & Shoshani, 1997[START_REF] Shoshani | Elephantidae phylogeny: morphological versus molecular results[END_REF], from which originate the Mammutida Tassy & Shoshani, 1997[START_REF] Shoshani | Elephantidae phylogeny: morphological versus molecular results[END_REF] and the Elephantida Tassy & Shoshani, 1997[START_REF] Shoshani | Elephantidae phylogeny: morphological versus molecular results[END_REF] Choerolophodon [START_REF] Schlesinger | Die Mastodonten des KK Naturhistorischen Hofmuseums[END_REF], the Amebelodontidae (e.g. Platybelodon [START_REF] Borissiak | On a new mastodon from the Chokrak Beds (middle Miocene) of the Kuban region. Platybelodon danovi n. gen. n. sp[END_REF] and Amebelodon [START_REF] Barbour | Preliminary notice on a new proboscidean Amebelodon fricki g[END_REF] and the Gomphotheriidae (e.g.

Gomphotherium

Burmeister, 1837, Anancus Aymard, 1855 and American gomphothers such as Stegomastodon [START_REF] Pohlig | Sur une vieille mandibule de" Tetracaulodon ohioticum" Blum., avec défense in situ[END_REF]Cuvieronius Osborn, 1923). On the other hand, the

Stegodontidae includes Stegodon

Falconer, 1847 and Stegolophodon Pohlig, 1888. Finally, the Elephantidae is the only family that still includes extant taxa (Elephas and Loxodonta). Among the elephantids are also found the mammoths Mammuthus [START_REF] Brookes | A catalogue of the anatomical and zoological museum of Joshua Brookes[END_REF]Palaeoloxodon Matsumoto, 1924. A simplified classification of the proboscideans presented here is given in Table 1.

The Proboscidea among the Afrotheria

As previously said, the origin of the Proboscidea is deeply rooted in Africa.

However, the African origin of the proboscideans is even earlier because they belong to a more inclusive clade of Introduction mammals that originates from Africa: the Afrotheria. The Afrotheria is a major clade of placental mammals that was recently recognized and defined by molecular studies of extant species (Dejong et al. 1981;[START_REF] Stanhope | Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals[END_REF]. It includes the extant orders Afrosoricida [START_REF] Stanhope | Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals[END_REF] (golden-moles and tenrecs), Tubulidentata Huxley, 1872 (aardvarks), Macroscelidea Butler, 1956 (elephantshrews), Hyracoidea [START_REF] Huxley | An introduction to the classification of animals[END_REF] (hyraxes), Sirenia Illiger, 1811 (sea-cows and dugongs) and the Proboscidea (Fig. 1).

The interordinal relationships in the Afrotheria are still debated, although some afrotherian clades such as the Paenungulata (extant Hyracoidea, Sirenia, Proboscidea; Fig. 1) are well supported. Macroscelidea and Afrosoricida are generally found closely related, forming the Afroinsectivora [START_REF] Springer | Molecules consolidate the placental mammal tree[END_REF][START_REF] Seiffert | A new estimate of afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence[END_REF]. However, the clade is not found in some other studies [START_REF] Stanhope | Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals[END_REF][START_REF] Seiffert | Diversity in the later Paleogene proboscidean radiation: a small barytheriid from the Oligocene of Dhofar Governorate, Sultanate of Oman[END_REF]). The most debated position is probably that of the Tubulidentata, which can be found as the sister-group of the Macroscelidea [START_REF] Stanhope | Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals[END_REF], as the sister group of the Afroinsectivora [START_REF] Springer | Molecules consolidate the placental mammal tree[END_REF] or as the sister group of the Paeunungulata [START_REF] Simpson | The principles of classification and a classification of mammals[END_REF][START_REF] Seiffert | A new estimate of afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence[END_REF][START_REF] Seiffert | Diversity in the later Paleogene proboscidean radiation: a small barytheriid from the Oligocene of Dhofar Governorate, Sultanate of Oman[END_REF]. The grouping of the orders Hyracoidea, Sirenia and Proboscidea in a clade called Paenungulata is supported by morphological, molecular [START_REF] Stanhope | Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals[END_REF]) and mixed data [START_REF] Seiffert | A new estimate of afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence[END_REF][START_REF] Seiffert | Diversity in the later Paleogene proboscidean radiation: a small barytheriid from the Oligocene of Dhofar Governorate, Sultanate of Oman[END_REF] [START_REF] Dercum | On the morphology of the semicircular canals[END_REF].

The investigation of the petrosal and inner ear of proboscideans is of great interest. Indeed, the elephants display several peculiarities related to the ear region. First, they are among the few mammals that display a unique perilymphatic foramen. In the vast majority of mammals, this foramen only exists during the early ontogeny and it divides into the fenestra cochleae and the aquaeductus cochleae. However, the single opening is retained in only few extant taxa: elephants, sirenians [START_REF] Fischer | Un trait unique de l'oreille des éléphants et des siréniens (Mammalia) : un paradoxe phylogénétique[END_REF] and the gray whale Eschrichtius robustus [START_REF] Geisler | The petrosal and inner ear of Herpetocetus sp. (Mammalia: Cetacea) and their implications for the phylogeny and hearing of archaic mysticetes[END_REF]. The undivided perilymphatic foramen was first considered a synapormorphy of the Tethytheria (it is also found in Arsinoitherium, [START_REF] Court | Periotic anatomy of Arsinoitherium (Mammalia, Embrithopoda) and its phylogenetic implications[END_REF], but this hypothesis was challenged by later discoveries of divided foramens in early sirenians and proboscideans [START_REF] Court | Anatomy of the periotic bone in the Eocene Proboscidean Numidotherium koholense : An example of parallel evolution in the inner ear of tethytheres[END_REF].

The elephants are also among the few mammals that are able to hear infrasound [START_REF] Payne | Infrasonic calls of the Asian elephant (Elephas maximus)[END_REF][START_REF] Poole | The social contexts of some very low frequency calls of African elephants[END_REF]. The study of the cochlear morphology of proboscideans is of great interest to trace back the evolutionary history of low frequency hearing in the Proboscidea.

Finally, some early representatives of the order, such as Barytherium and Moeritherium, are generally believed to be semi-aquatic [START_REF] Liu | Stable isotope evidence for an amphibious phase in early proboscidean evolution[END_REF], while others Introduction such as Numidotherium exhibit adaptations to terrestrial life [START_REF] Mahboubi | Was the Early Eocene proboscidean Numidotherium koholense semi-aquatic or terrestrial? Evidence from stable isotopes and bone histology[END_REF]. Studies of the early embryology of elephants suggests that the elephant's ancestors were aquatic [START_REF] Gaeth | The developing renal, reproductive, and respiratory systems of the African elephant suggest an aquatic ancestry[END_REF], based on observation of the development of the nephrostomes.

However, this can be due to the very long gestation of elephants (22 months;[START_REF] Sikes | Natural history of the African elephant[END_REF]. The aquatic ancestry of proboscideans is still debated today and the study of the functional capacities of the vestibular system in the Proboscidea can provide new clues on their sensory perception of the environment.

The ear region of the Proboscidea in science: a 300-year history

The ear region of proboscideans has not been thoroughly studied in the past. However, it has been of very early interest in the scientific community, the earliest study focused on the subject that we could trace back being 300 years old. It consists of an anatomical description of the ear region of an extant elephant [START_REF] Blair | A description of the organ of hearing in the elephant, with the figures and situation of the ossicles, labyrinth and cochlea, in the ear of that large animal[END_REF](Blair, -1719)). This study was published several years after Blair described the whole skeleton of the elephant in his

Osteographia Elephantina (Blair, 1710(Blair, -1712a;;1710-1712b) in which he describes the ear region only briefly. In the 1717-1719 publication, however, the general anatomy of the ear region is thoroughly described. The description is accompanied by an anatomical chart, but the illustrations seem not very accurate (Fig. 2A). For the next century, the subject seems to have been forsaken by the scientific community. The labyrinth of elephant was later reappraised by Fick (1844); however we could not have access to the publication. The next year, the labyrinth is compared to that of other mammals in a comprehensive comparative anatomy work [START_REF] Hyrtl | Vergleichend-anatomische Untersuchungen über das innere Gehörorgan des Menschen und der Säugethiere[END_REF].

More precise illustrations of the bony labyrinth and the ossicles are given (Fig. 2B). Twenty years later, the study of the bony labyrinth of Deinotherium giganteum is the first known attempt to describe the bony labyrinth of an extinct member of the Proboscidea (Claudius, 1865). The fossil labyrinth is compared with that of the extant Asian elephant as well as with other mammals using accurate anatomical drawings (Fig. 2C). This marks the end of the early studies on the bony labyrinth of

Introduction

In his work on the muscles and blood vessels of the Asian elephant head, [START_REF] Watson | Contributions to the Anatomy of the Indian Elephant: Part IV. Muscles and Blood-Vessels of the Face and Head[END_REF] describes several soft structures linked to the ear region, such as the internal carotid artery or the muscles of the external ear. The bones of the ear region of the extant elephant are again described in three related publications [START_REF] Buck | A contribution to the anatomy of the elephant's ear[END_REF]1890;[START_REF] Richards | A further report on the anatomy of the elephant's ear[END_REF].

Several interesting considerations are made, but these studies lack proper illustrations of the petrosal. A few elements of the anatomical descriptions are addressed in Chapter II. Finally, a few details on the petrosal of a fetus of African elephant are given in [START_REF] Eales | XI.-The Anatomy of the Head of a Foetal African Elephant, Elephas africanus (Loxodonta africana)[END_REF]. Except for the early description of the bony labyrinth of Deinotherium giganteum (Claudius, 1865), the ear region of extinct proboscideans has been investigated only recently. A natural endocast of the cochlea is briefly described in a Moeritherium skull from the Eocene of Libya [START_REF] Tassy | Le crâne de Moeritherium (Proboscidea, Mammalia) de l'Eocène de Dor El Talha (Libye) et le problème de la classification phylogénétique du genre dans les Tethytheria McKenna[END_REF].

The study of the petrosal ontogeny of elephants and sirenians reveals a shared peculiar feature of both mammalian orders: the undivided perilymphatic foramen retained in adult life. This is first hypothesized as a synapomorphy of the Tethytheria, especially as the embrithopod Arsinoitherium (an extinct relative of the tethytheres) displays the same characteristic [START_REF] Court | Periotic anatomy of Arsinoitherium (Mammalia, Embrithopoda) and its phylogenetic implications[END_REF]. However, investigations of the petrosal of the early proboscidean Numidotherium [START_REF] Court | Anatomy of the periotic bone in the Eocene Proboscidean Numidotherium koholense : An example of parallel evolution in the inner ear of tethytheres[END_REF] shows that this morphology is convergent, since the perilymphatic foramen is divided into the fenestra cochleae and the aquaeductus cochleae in Numidotherium. On the other hand, a later study of the bony labyrinth of Numidotherium suggests that they were not adapted to low frequency hearing as extant elephants [START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF]. The petrosal of Moeritherium is described for the first time by [START_REF] Court | The periotic of Moeritherium (Mammalia, Proboscidea) : homology or homoplasy in the ear region of Tethytheria McKenna[END_REF]. It displays the undivided perilymphatic foramen which challenged the phylogenetic position of Moeritherium admitted at that time, which was believed to be less derived than Numidotherium. Finally, the petrosal of Gomphotherium angustidens is described in details in [START_REF] Tassy | L'anatomie cranio-mandibulaire de Gomphotherium angustidens (Cuvier, 1817) (Proboscidea, Mammalia) : données issues du gisement d'En Péjouan (Miocène moyen du Gers, France)[END_REF] CT scan methods by Schmitt & Gheerbrant (2016). This paper is actually part of this PhD thesis, its unmodified version is presented in the Chapter I.

The development of new methods of investigation of the petrosal and the bony labyrinth of proboscideans hence opened new work perspectives on this complex yet critical anatomical region.

However, there are still a lot of grey areas.

Even though the elephants are emblematic extant animals, a modern comprehensive study of their petrosal and bony labyrinth has not been carried out yet. Detailed illustrations of the petrosal anatomy and 3D reconstructions of their bony labyrinth have not been published.

The variability of this anatomical region has been studied in elephantimorphs [START_REF] Ekdale | Morphological variation in the ear region of Pleistocene Elephantimorpha (Mammalia, Proboscidea) from Central Texas[END_REF], but it is still unknown in extant elephants. In addition, the petrosal and inner ear anatomy of the majority of extinct proboscideans has yet to be described.

Objectives

The main objective of this work is Comparisons of these taxa with other proboscideans and some other orders allow formalizing primary homologies of ear evolution. The morphological variation of the bony labyrinth is then investigated using geometric morphometrics in Chapter IV. This method allows quantifying morphological resemblances between taxa and investigating the effect of allometry on the bony labyrinth morphology of proboscideans. Moreover, this step is helpful in formalizing new primary homologies for the purpose of a phylogenetic analysis of the Proboscidea.

The study of the evolution of the ear region characters within the Proboscidea (and to a lesser extent within the Afrotheria) is conducted in Chapter V, using cladistic methods. The functional capacities of the vestibular system of extant afrotherians are investigated using a very recent and original method (David et al. in press). Based on this new approach, the functional capacities of the semicircular system of extinct proboscideans are inferred. Finally, a preliminary study of the evolution of audition within proboscideans is conducted.

Introduction

Material and methods

Material

As previously said, the main objective of this PhD thesis is to highlight the morphological variability of the petrosal and inner ear in Proboscidea. To do so, many proboscideans specimens and some outgroups were CT-scanned. Table 2 summarizes the scanned specimens in this study. Only classification details, the collection number and scanning properties are given. The material will be presented with more details in the next related chapters.

The earliest known proboscideans

Eritherium and Phosphatherium were previously scanned and partially studied during my Master's thesis. A further presentation of these specimens is given in the "Material and methods" section of Chapter I.

Several skulls of extant elephants were also scanned in order to study the intraspecific variability of the ear region in Proboscidea. Further details about these specimens are given in the "Material and methods" section of Chapter II.

Finally, several fossil taxa of proboscideans and outgroups were scanned in order to study the evolution of this anatomical region. The subsequent material is presented in the "Material and methods" section of Chapter III.

As presented in Table 2,

Methods

CT scanning acquisitions and segmentation

The specimens were scanned with different microtomographs. Details about the location of the scanners, the models of the microtomographs and the different resolutions are given in Table 2. The petrosals and bony labyrinths were then segmented at the 3D imagery platform of MNHN using MIMICS INNOVATION SUITE software (Materialise, releases 16 and 17 depending on the specimen). Further details about the post-treatment of the 3D models for specific purposes will be explained in the "Material and methods" section of the related chapter (chapters IV and V mostly).

Petrosal and labyrinth measurements

Angle between the cerebral and cerebellar surfaces of the petrosal

The dorsal surface of the petrosal of the major part of the proboscideans (elephantimorphs) displays two well distinct surfaces: the cerebellar surface and the cerebral surface. The two surfaces are separated by a ridge called the crista partis petrosa. To calculate the angle between these surfaces, we orient the petrosal in posterior view. Then we trace a line starting from the crista partis petrosa and following the cerebellar surface and a line starting from the crista partis petrosa and following the cerebral surface (Fig. 3A). The angle between these two lines is then measured manually.

Stapedial ratio of the fenestra vestibuli

The stapedial ratio is calculated according to [START_REF] Segall | Morphological parallelisms of the bulla and auditory ossicles in some insectivores and marsupials[END_REF]: r = L/w with L = length and w = width of the fenestra vestibuli (Fig. 3B). It expresses the general shape of the fenestra vestibuli. Specimens with high ratios tend to display a relatively oval fenestra vestibuli while specimens with low ratios generally display a rounder fenestra vestibuli.

Aspect ratio of the cochlea

The aspect ratio of the cochlea has been calculated using the same method described in Benoit et al. (2013b). The width of the cochlea is measured from the basal hook to the periphery of the cochlear canal in ventral view (Fig. 3C).

The height of the cochlea is measured in profile view.

Introduction Figure 3 : Measurement protocols. Angle between the cerebellar and cerebral surfaces of the petrosal (A). Stapedial ratio (B) following [START_REF] Segall | Morphological parallelisms of the bulla and auditory ossicles in some insectivores and marsupials[END_REF]; w=width, L=length. Cochlear aspect ratio (C) following Benoit et al. (2013b); W=width, H=height. Number of turns of the cochlea (D) following [START_REF] West | The relationship of the spiral turns of the cochlea and the length of the basilar membrane to the range of audible frequencies in ground dwelling mammals[END_REF]. Angle between the major axis of the semicircular canal and the crus commune (E and F).

Number of turns of the cochlea

The number of turns of the cochlea was calculated using the protocol of [START_REF] West | The relationship of the spiral turns of the cochlea and the length of the basilar membrane to the range of audible frequencies in ground dwelling mammals[END_REF]. A line is drawn between the basal hook of the cochlea and the modiolus (rotation axis of the cochlea; Fig. 3D).

Then, the number of times that the cochlea crosses that line is counted as a half-turn and the total number of turns of the cochlea is calculated.

Angle between the major axis of the semicircular canals and the crus commune

This angle value can only be calculated for the vertical semicircular canals (anterior and posterior canals). It is pertinent only for canals exhibiting an oval overall shape. The specimen should be oriented so that its anatomical plane is the plane of the screen. A line is drawn following the major axis (greater radius) of the ellipse formed by the canal. Another Introduction line is drawn following the axis of the crus commune. The angle between these two lines is then measured manually (Fig. 3E and3F). If the line following the major axis of the canal crosses the line of the crus commune at the level of the crus basis, the value is considered to be positive (Fig. 3E).

On the contrary, if the major axis of the canal crosses the line of the crus commune at the level of the crus apex, the value is considered to be negative (Fig. 3F).

Landmark protocol

The functional analysis of the semicircular canals requires a certain number of landmarks placed on the bony labyrinth. The landmarks are then used to calculate several measurements. Based on these measurements and measurements on the membranous labyrinth of closely related specimens (chapter VI), functional features can be inferred. Several portions of this PhD thesis are based on these landmarks. Indeed, we used the same landmark sets to conduct a geometric morphometrics analysis (chapter IV). On the other hand, we used several measurements of the bony labyrinth based on these landmarks and given by an ARIADNE add-on currently developed by Romain David to compare our specimens (chapter II and III). These compared measurements were sometimes used to create or recalibrate phylogenetic characters (chapter V). Some of the measurements used in chapters II and III have been obtained with these landmarks.

Every complete (or almost complete) inner ear that has been segmented for this work has been landmarked following a modified version of the protocol presented in [START_REF] Gunz | The mammalian bony labyrinth reconsidered, introducing a comprehensive geometric morphometric approach[END_REF]. This protocol consists of 13 landmark sets (Fig. 4A). The landmarks were placed on the specimens using the software AVIZO 7.1.1. The Auto-Skeleton tool was used to obtain the central streamlines of the semicircular canals.

First, an external set of landmarks for each semicircular canal is placed (Fig. 4B-D, black sets). The first landmark is a type-I landmark and it is located on the ventral part of the ampulla. It is centered on the symmetry axis of the canal and placed at the external level of the crista ampullaris (at this place, the nervus ampullaris usually enters the ampulla).

Semi-landmarks are placed along the canal following its most external portion until its connection with the crus commune. Three of these sets are placed on the inner ear (one on each semicircular canal). Three of these sets are placed on the inner ear (one on each semicircular canal).

Concerning the lateral canal, when it is partially fused with the posterior canal (partial or total 'crus commune secundaria'), the last landmark is placed on the streamline before the canals begin to fuse. In this case, the last remaining landmarks are placed in the "slenderutricle intersection" set (next paragraph).

An internal set of landmarks is placed at the intersection between the lateral canal and the lateral utricle (Fig.

Volumes and landmark-based measurements

As previously said, the ARIADNE add-on currently developed by Romain David outputs several measurements of the bony labyrinths than can be helpful to compare specimens. Because these measurements were used in several following chapters of the thesis (comparative anatomy chapters II and III and phylogenetics chapter V), they are presented in this section.

Introduction

Volumes

The total volume of the bony labyrinth is directly given (in mm 3 ) by the ARIADNE add-on currently developed by Romain David. The volume of the cochlear part only is also available. The cochlea is separated from the vestibular part of the labyrinth at the beginning of the preparation protocol required for the software. The limit is drawn using the software GEOMAGICS Studio 2012 (Fig. 5).

It is important to include the superior extremity of the cochlear canal as well as the fenestra vestibuli in the cochlear volume. On the other hand, the saccule must be included in the vestibule volume.

During the comparison of the specimens, we essentially used the relative volume of the cochlea (cochlear volume / total volume * 100). It is very difficult to separate the cochlea from the vestibule in the same way. Hence, these values are somewhat approximate and cannot be used in proper statistical analysis.

However, approximate relative volumes of the cochlea obtained with this protocol and given in the literature using other protocol can be compared within a certain range of precision.

Crus commune length, average section radius and average thickness ratio

The crus commune length is measured by the ARIADNE add-on currently in development. It simply consists of the sum of the distances between consecutive internal landmarks of the crus commune. The average section radius is given by the software as well. It is the mean of the crus commune radii taken at different sections of the crus commune.

We used these two values to calculate the average thickness ratio (average section radius / crus commune length * 100). This ratio gives a quantitative value that expresses the global thickness of the crus commune. Crus commune with a high ratio tend to be thicker and stockier than crus commune with a low ratio.

Semicircular canals length, average section radius and thickness ratio

The semicircular canal length is measured by the ARIADNE add-on as well.

It is the sum of the distances between consecutive landmarks of the whole canal.

As for the anterior and posterior canals, For the lateral canal, the measurement starts at the first internal landmark of the ampulla and ends at the last landmark of the lateral canal / lateral utricle intersection set (red landmark in Fig. 4A and 4D). The average section radius is calculated in the same manner as for the crus commune average section radius. It only expresses the mean section radius of the slender part of the canal (green, dark blue and sky blue in Fig. 4). Indeed, the ampullae radii are not used to calculate this value. Using these two values given by the ARIADNE add-on, an average thickness ratio of each semicircular canal can be calculated (average section radius / semicircular canal length * 100). The mean of these three ratios expresses the global thickness of the semicircular canals quantitatively.

Radii of curvature

The radius of curvature of each semicircular canal is given directly by the

Angle between the semicircular canals

The angles between the semicircular canals are given by the ARIADNE add-on under development.

Measuring manually these angles can be tricky, because the semicircular canals are rarely perfectly planar. The software uses the landmarks to determine the functional plane of each semicircular canal. The angles are then compared between the functional planes of the canals.

I -The ear region of earliest known elephant relatives

Introduction

Today there are only three living species of proboscideans: the Asian elephant (Elephas maximus), the African bush elephant (Loxodonta africana) and the African forest elephant (Loxodonta cyclotis). The fossil diversity of this mammalian order is much greater:

approximately 180 extinct species of proboscideans have been described [START_REF] Gheerbrant | L'origine et l'évolution des éléphants[END_REF], with a rich evolutionary history dating as far back as 60 million years [START_REF] Gheerbrant | Paleocene emergence of elephant relatives and the rapid radiation of African ungulates[END_REF]. The

Material and methods

Material studied

Eritherium azzouzorum from the Selandian of the Ouled Abdoun Basin (Morocco) is the only known species of the genus Eritherium and is the oldest known proboscidean. It is represented by some elements of the skull and most of the dentition [START_REF] Gheerbrant | Paleocene emergence of elephant relatives and the rapid radiation of African ungulates[END_REF][START_REF] Gheerbrant | Dental and cranial anatomy of Eritherium azzouzorum from the Paleocene of Morocco, earliest known proboscidean mammal[END_REF]). The isolated petrosal described in this study was mentioned by [START_REF] Gheerbrant | Dental and cranial anatomy of Eritherium azzouzorum from the Paleocene of Morocco, earliest known proboscidean mammal[END_REF], as specimen PM88, but was not described or Phosphatherium escuilliei was discovered in early Ypresian phosphate beds of the Ouled Abdoun Basin (Morocco) [START_REF] Gheerbrant | A Paleocene proboscidean from Morocco[END_REF][START_REF] Gheerbrant | Les localités à mammifères des carrières de Grand Daoui, bassin des Ouled Abdoun, Maroc, Yprésien: premier état des lieux[END_REF][START_REF] Gheerbrant | Nouvelles données sur Phosphatherium escuilliei (Mammalia, Proboscidea) de l'Eocène inférieur du Maroc, apports à la phylogénie des Proboscidea et des ongulés lophodontes[END_REF]. Dental and cranial remains have been found, and a description and reconstruction of the whole skull was provided by [START_REF] Gheerbrant | Nouvelles données sur Phosphatherium escuilliei (Mammalia, Proboscidea) de l'Eocène inférieur du Maroc, apports à la phylogénie des Proboscidea et des ongulés lophodontes[END_REF]. It skull with both right and left petrosals preserved [START_REF] Gheerbrant | Nouvelles données sur Phosphatherium escuilliei (Mammalia, Proboscidea) de l'Eocène inférieur du Maroc, apports à la phylogénie des Proboscidea et des ongulés lophodontes[END_REF]Fig. I.3). However, the promontorium is damaged on both petrosals which prevented the reconstruction of the entire cochlea. In this work we reconstruct and describe mostly the right petrosal (and labyrinth) of MNHN.F.PM17, because it is the better preserved one. The right petrosal (the left is missing) of specimen OCP DEK/GE 305 of Phosphatherium escuilliei seems to be better preserved [START_REF] Gheerbrant | Nouvelles données sur Phosphatherium escuilliei (Mammalia, Proboscidea) de l'Eocène inférieur du Maroc, apports à la phylogénie des Proboscidea et des ongulés lophodontes[END_REF]; Figs 1 and2) with an undamaged promontorium, but this specimen housed in the OCP collection (Khouribga, Morocco) was not available for CT scanning.

CT scanning acquisition

The two studied specimens of

Systematic descriptions

3.1.

Eritherium azzouzorum Gheerbrant, 2009

The left petrosal PM88 of Eritherium azzouzorum was found broken and isolated, but in association with several other skull fragments [START_REF] Gheerbrant | Dental and cranial anatomy of Eritherium azzouzorum from the Paleocene of Morocco, earliest known proboscidean mammal[END_REF]. It was oriented indirectly based on comparisons with the petrosals of Protungulatum (O' Leary, 2010) and Ocepeia [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF]. which drained the venous blood from brain [START_REF] Cifelli | The petrosal structure of Hyopsodus with respect to that of some other ungulates, and its phylogenetic implications[END_REF]. The cochlear canaliculus (aquaeductus cochleae)

Cerebellar surface

The

connects the perilymphatic space of the inner ear to the subarachnoid space of the endocranial cavity [START_REF] Meng | Osseous inner ear structures and hearing in early marsupials and placentals[END_REF]. In specimen PM88 of Eritherium it was likely located in the large fissure that runs across the petrosal, which renders observation and reconstruction difficult.

However, despite the fact that this area is damaged by the fissure, we observed a foramen at the level of the jugular fossa (medial surface) that likely corresponds to the cochlear canaliculus. The aquaeductus vestibuli exits perpendicularly to the cerebellar surface and medially to the subarcuate fossa. The tegmen tympani is massive and carries two large grooves. The one that is the closest to the subarcuate fossa is probably the sigmoid sinus, observed in Orthaspidotherium [START_REF] Ladevèze | First skull of Orthaspidotherium edwardsi (Mammalia, 'Condylarthra') from the late Paleocene of Berru (France) and phylogenetic affinities of the enigmatic European family Pleuraspidotheriidae[END_REF]). The other one is probably the prootic sinus.

Tympanic surface

In ventrolateral view (Fig for the stapedial artery [START_REF] Wible | The internal carotid artery in early eutherians[END_REF]. On the posterior part of the petrosal, the pars mastoidea is square and prominent.

In dorso-lateral view (Fig The observation of Eritherium in tomographic section shows the presence of a well-developed pneumatization of its petrosal, with the presence of numerous and large osseous cells, especially inside the tegmen tympani (see Appendix 2,character 11).

Inner ear

The I.1.

Phosphatherium escuilliei

Eritherium Phosphatherium

Stapedial ratio Henkelotherium), in order to assess their evolution and their significance and throw light on the ancestral morphotype of the order Proboscidea.

Cladistic analysis of petrosal and inner ear features of Eritherium and Phosphatherium among Proboscidea

The matrix analyzed here contains

Lamina secundaria

Present on the three quarters of the first turn Present on the first half-turn but less deep Among the 18 characters, two have more than two states ( [1], [START_REF]Definition of the ampullae: (0) well-defined and bulbous, (1) poorly defined 14. Basal thickening of the crus commune: (0) absent or slight,(1) pyramidal in shape 15. Thickness of the crus commune: (0) slender, thickness ratio[END_REF]) and both of them were unordered. 2010), Diacodexis [START_REF] Orliac | The inner ear of Diacodexis, the oldest artiodactyl mammal[END_REF][START_REF] Orliac | Comparative anatomy of the petrosal bone of Dichobunoids, early members of Artiodactylamorpha (Mammalia)[END_REF] and Dasypus [START_REF] Wible | Petrosal anatomy of the nine-banded armadillo, Dasypus novemcinctus Linnaeus, 1758 (Mammalia, Xenarthra, Dasypodidae)[END_REF]Ekdale, 2013). Henkelotherium [START_REF] Ruf | Petrosal anatomy and inner ear structures of the late Jurassic Henkelotherium (Mammalia, Cladotheria, Dryolestoidea): insight into the early evolution of the ear region in cladotherian mammals[END_REF]) and zhelestids [START_REF] Ekdale | Petrosal bones of placental mammals from the Late Cretaceous of Uzbekistan[END_REF][START_REF] Ekdale | Morphology and variation within the bony labyrinth of zhelestids (Mammalia, Eutheria) and other therian mammals[END_REF]Ekdale, 2013) were used as therian and eutherian outgroups. However, this analysis showed a strong homoplasy among afrotherians Moeritherium [START_REF] Court | The periotic of Moeritherium (Mammalia, Proboscidea) : homology or homoplasy in the ear region of Tethytheria McKenna[END_REF],

Numidotherium [START_REF] Court | Anatomy of the periotic bone in the Eocene Proboscidean Numidotherium koholense : An example of parallel evolution in the inner ear of tethytheres[END_REF][START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF]Benoit et al. 2013b),

Gomphotherium [START_REF] Tassy | L'anatomie cranio-mandibulaire de Gomphotherium angustidens (Cuvier, 1817) (Proboscidea, Mammalia) : données issues du gisement d'En Péjouan (Miocène moyen du Gers, France)[END_REF] Zhelestids [START_REF] Ekdale | Petrosal bones of placental mammals from the Late Cretaceous of Uzbekistan[END_REF][START_REF] Ekdale | Morphology and variation within the bony labyrinth of zhelestids (Mammalia, Eutheria) and other therian mammals[END_REF]Ekdale, 2013) and (2013c). Another synapomorphy is the increase in the number of turns of the cochlea from less than one and a half turn [17(0)] to two turns or more [17(1)].

Henkelotherium
However, this feature may not be very significant because previous studies (Ekdale, 2013) showed that it varies intraspecifically. However, this character is not used in our study because it cannot be observed on the isolated petrosal of Eritherium, and it is most probably a plesiomorphic trait known in many placentals and eutherians [START_REF] Gheerbrant | Nouvelles données sur Phosphatherium escuilliei (Mammalia, Proboscidea) de l'Eocène inférieur du Maroc, apports à la phylogénie des Proboscidea et des ongulés lophodontes[END_REF][START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF].

Phosphatherium

Fossa subarcuata

The fossa subarcuata is a depression on the cerebellar surface of the petrosal which houses the paraflocculus of the cerebellum [START_REF] Cifelli | The petrosal structure of Hyopsodus with respect to that of some other ungulates, and its phylogenetic implications[END_REF]. The great depth [1(0)] of the [START_REF] Wible | Earliest eutherian ear region: a petrosal referred to Prokennalestes from the early cretaceous of Mongolia[END_REF][START_REF] Wible | New data on the skull and dentition in the Mongolian late Cretaceous eutherian mammal Zalambdalestes[END_REF](Wible et al. , 2009) ) and in early afrotherians such as Ocepeia [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF]. A synapomorphic moderate infilling [1(1)] of the fossa is observed in

Phosphatherium (Appendix 2) and
Numidotherium, whereas the infilling of the fossa becomes complete [1(2)] in the clade {Moeritherium [Gomphotherium (Elephantidae)]}. This progressive infilling of the fossa is a convergent trend in several afrotherian lineages such as macroscelideans, tubulidentates (Benoit et al. 2013c), embrithopods [START_REF] Court | Periotic anatomy of Arsinoitherium (Mammalia, Embrithopoda) and its phylogenetic implications[END_REF] and sirenians (Benoit et al. 2013a).

Perilymphatic foramen

In most adult mammals, the fenestra cochleae and the cochlear canaliculus are two distinct openings. In the early stages of embryological development, however, the petrosal bears only one opening, the perilymphatic foramen. It divides later during the development as a separate fenestra cochleae and cochlear canaliculus [START_REF] Fischer | Un trait unique de l'oreille des éléphants et des siréniens (Mammalia) : un paradoxe phylogénétique[END_REF]. These two foramina [2(0)] are present in early eutherians and almost all mammals (Table I.3), corresponding to a plesiomorphic state in placentals and afrotherians. Early afrotherians such as

Ocepeia also display two separated foramina [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF]. In some afrotherians, however, the perilymphatic foramen is not divided and is retained at the adult stage. This is observed in extant sirenians and proboscideans, and in the embrithopod Arsinoitherium [START_REF] Court | Periotic anatomy of Arsinoitherium (Mammalia, Embrithopoda) and its phylogenetic implications[END_REF][START_REF] Fischer | Un trait unique de l'oreille des éléphants et des siréniens (Mammalia) : un paradoxe phylogénétique[END_REF]. This led to their grouping in the clade Tethytheria. However, later palaeontological discoveries showed that the non-division of the perilymphatic foramen [2(1)] is a convergent character.

Indeed, early proboscideans such as

Phosphatherium [START_REF] Gheerbrant | Nouvelles données sur Phosphatherium escuilliei (Mammalia, Proboscidea) de l'Eocène inférieur du Maroc, apports à la phylogénie des Proboscidea et des ongulés lophodontes[END_REF] and Numidotherium [START_REF] Court | Anatomy of the periotic bone in the Eocene Proboscidean Numidotherium koholense : An example of parallel evolution in the inner ear of tethytheres[END_REF] and early sirenians such as Prorastomus (Benoit et al. 2013a) [START_REF] Wible | The Eutherian Mammal Maelestes gobiensis from the late Cretaceous of Mongolia and the phylogeny of Cretaceous eutherian[END_REF][START_REF] Benoit | Comparative anatomy and three-dimensional geometric-morphometric study of the bony labyrinth of Bibymalagasia (Mammalia, Afrotheria)[END_REF], Tubulidentata represented by Orycteropus (Benoit et al. 2013b;Ekdale, 2013), Ocepeia [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF], Hyracoidea represented by Procavia (Benoit et al. 2013b;Ekdale, 2013), Embrithopoda represented by Arsinoitherium [START_REF] Court | Periotic anatomy of Arsinoitherium (Mammalia, Embrithopoda) and its phylogenetic implications[END_REF]Benoit et al. 2013b), Sirenia represented by Trichechus (Benoit et al. 2013a;Ekdale, 2013), Prorastomus and the sirenian of Chambi (Benoit et al. 2013a), and nonafrotherian placentals represented by Protungulatum [START_REF] Wible | The Eutherian Mammal Maelestes gobiensis from the late Cretaceous of Mongolia and the phylogeny of Cretaceous eutherian[END_REF][START_REF] O'leary | An anatomical and phylogenetic study of the osteology of the petrosal of extant and extinct artiodactylans (Mammalia) and relatives[END_REF], Diacodexis [START_REF] Orliac | The inner ear of Diacodexis, the oldest artiodactyl mammal[END_REF][START_REF] Orliac | Comparative anatomy of the petrosal bone of Dichobunoids, early members of Artiodactylamorpha (Mammalia)[END_REF] and Dasypus [START_REF] Wible | Petrosal anatomy of the nine-banded armadillo, Dasypus novemcinctus Linnaeus, 1758 (Mammalia, Xenarthra, Dasypodidae)[END_REF]Ekdale, 2013). The therians and eutherians Henkelotherium [START_REF] Ruf | Petrosal anatomy and inner ear structures of the late Jurassic Henkelotherium (Mammalia, Cladotheria, Dryolestoidea): insight into the early evolution of the ear region in cladotherian mammals[END_REF], zhelestids [START_REF] Ekdale | Petrosal bones of placental mammals from the Late Cretaceous of Uzbekistan[END_REF][START_REF] Ekdale | Morphology and variation within the bony labyrinth of zhelestids (Mammalia, Eutheria) and other therian mammals[END_REF]Ekdale, 2013) and Zalambdalestes [START_REF] Wible | The Eutherian Mammal Maelestes gobiensis from the late Cretaceous of Mongolia and the phylogeny of Cretaceous eutherian[END_REF]Ekdale & Rowe,2011). In bold, ancestral states found in Eritherium and Phosphatherium.

Fenestra vestibuli

The fenestra vestibuli is the opening which bears the footplate of the stapes in life. The stapes touches the petrosal at the level of this opening and transmits the auditory message to the cochlea and the organ of Corti. The shape of the fenestra vestibuli varies between taxa and the stapedial ratio [START_REF] Segall | Morphological parallelisms of the bulla and auditory ossicles in some insectivores and marsupials[END_REF] yields a value for this shape variation. The fenestra vestibuli (Table I.3) seems to be primitively oval [3(0)] because many nonplacental eutherians such as

Zalambdalestes have an oval fenestra vestibuli [START_REF] Wible | New data on the skull and dentition in the Mongolian late Cretaceous eutherian mammal Zalambdalestes[END_REF]. It is also oval in early afrotherians such as Ocepeia [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF]). This opening is generally round [3(1)] in Paenungulata but there are exceptions such as

Numidotherium (Benoit et al. 2013b), the sirenian from Chambi (Benoit et al. 2013a) and some fossil elephantimorphs [START_REF] Ekdale | Morphological variation in the ear region of Pleistocene Elephantimorpha (Mammalia, Proboscidea) from Central Texas[END_REF]. The stapedial ratio was used as a character in several phylogenetic studies based on the petrosal anatomy (Benoit et al. 2013a-c). However, this ratio can be extremely variable in some taxa; for example, it varies from 1.4 to 2.1 in an elephantimorph sample bearing almost only Mammuthus [START_REF] Ekdale | Morphological variation in the ear region of Pleistocene Elephantimorpha (Mammalia, Proboscidea) from Central Texas[END_REF] and potentially a few Mammut petrosals. This character is therefore questionable for taxonomic comparisons and phylogenetic studies, which might explain its homoplasy in our analysis (CI = 0.500). In the Proboscidea, the fenestra vestibuli seems to be primitively wide [4(0)] (Table I.3) and becomes small [4(1)] in Numidotherium and Phosphatherium (Appendix 2), resulting in the grouping of these two taxa as a clade. However, the size of the fenestra vestibuli is probably also variable, just like the stapedial ratio, and its phylogenetic significance is therefore questionable.

Crus commune secundaria

The fusion of the lateral and posterior canal (Table I.3) as a true crus commune secundaria [13(0)] seems to be plesiomorphic as it is found in many nonplacental eutherian mammals such as Zalambdalestes and Kulbeckia, and even in dryolestids such as Henkelotherium [START_REF] Ruf | Petrosal anatomy and inner ear structures of the late Jurassic Henkelotherium (Mammalia, Cladotheria, Dryolestoidea): insight into the early evolution of the ear region in cladotherian mammals[END_REF]. In Eritherium (Appendix 2), the canals are not fully merged but are partly fused [13(1)] as in Ocepeia (Gheerbrant et al. 2014); the fusion of the canals appears to be more advanced in Eritherium than in Ocepeia [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF] However, the canals are more separated in Elephantidae [13(2)] than in Eritherium

Aspect of the semi-circular canals

The evolution of the thickness of the bony semi-circular canals seems to be quite simple (Table I

Number of turns of the cochlea

The number of turns of the cochlea (Table I.3) has been used in several phylogenetic analyses (Ekdale, 2013).

Almost every therian mammal possesses at least one full turn of the cochlea [START_REF] Meng | Osseous inner ear structures and hearing in early marsupials and placentals[END_REF]. The primitive state for Afrotheria seems to be a cochlea with at least two turns. Even the earliest known afrotherian, Ocepeia, has two full turns [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF]). Among afrotherians, only Trichechus shows a very small number of turns (inferior to 1.5 turns) which seems to be autapomorphic.

All proboscideans studied with CT scan methods show at least one and a half turns [START_REF] Ekdale | Morphological variation in the ear region of Pleistocene Elephantimorpha (Mammalia, Proboscidea) from Central Texas[END_REF]Benoit et al. 2013b).

The cochlea of Eritherium has two turns but that of Phosphatherium is damaged so the number of turns remains unknown (Appendix 2). Numidotherium displays the lowest number of turns among Proboscidea, 1.62 turns (Benoit et al. 2013b), and Elephantidae has at least two turns [START_REF] Ekdale | Morphological variation in the ear region of Pleistocene Elephantimorpha (Mammalia, Proboscidea) from Central Texas[END_REF]Benoit et al. 2013b).

However, it should be noted that the number of turns can vary within the same species (Ekdale, 2013), with a variability up to 360° (one full turn). Without a study of intra-specific variability of the inner ear of proboscideans and afrotherians, a difference of < 1 turn in the cochlear coiling seems to be of low significance for systematics and phylogeny.

Secondary bony lamina

The secondary bony lamina (or lamina secundaria) is primitively present in non-placental eutherian mammals [18(0)] (Table I

Conclusion

The

Introduction

The petrosal of extant elephants is difficult to observe when it is still in connection within the skull. Indeed, it is located rather internally in the skull and it is covered by other bones when the skull is viewed ventrally. Isolated petrosals of extant elephants are rarely found in collections because this bone is fused with other bones of the skull. Nonetheless, the anatomy of the ear region of extant elephants has been investigated early in the past [START_REF] Blair | A description of the organ of hearing in the elephant, with the figures and situation of the ossicles, labyrinth and cochlea, in the ear of that large animal[END_REF](Blair, -1719;;[START_REF] Hyrtl | Vergleichend-anatomische Untersuchungen über das innere Gehörorgan des Menschen und der Säugethiere[END_REF][START_REF] Buck | A contribution to the anatomy of the elephant's ear[END_REF][START_REF] Buck | A revised description of the anatomy of the elephant's ear[END_REF][START_REF] Richards | A further report on the anatomy of the elephant's ear[END_REF][START_REF] Fischer | Un trait unique de l'oreille des éléphants et des siréniens (Mammalia) : un paradoxe phylogénétique[END_REF]. However, this anatomical region remains poorly illustrated in elephants.

There are no complete illustrations of the petrosal anatomy in the literature. The This is also helpful for a critical review of previously used phylogenetic characters and for the identification of new ones.

Material and methods

Material

The specimens of extant elephants used in this study are listed in Table II.1. In addition, we mention which side of the skull was scanned and segmented, as well as the ossicles that were found within the tympanic cavity. However, two species of Loxodonta are recognized today [START_REF] Frade | Ordre des proboscidiens (Proboscidea Illiger, 1811)[END_REF]. The measurements [START_REF] Spoor | The primate semicircular canal system and locomotion[END_REF]) but the inner ear was never actually segmented.

Elephas

The microtomographic data was given to us by Fred Spoor and the specimen was added to the sample. It is from Kenya and and unarguably belongs to the species Loxodonta africana.

Methods

CT scanning and segmentation

The skulls were scanned at the

Membranous labyrinth

As mentioned above, the specimen The bony and membranous labyrinths were then segmented using the same software than for the other specimens.

Measurements

The measurement protocol for the bony ears of extant elephants is the same than for the fossil sample. A general paragraph explaining all the measurement is available in the main 'Material and methods' section of the thesis.

Anatomical descriptions

Petrosal

The

Cerebellar surface

The cerebellar surface of the petrosal is more or less flat. In cerebellar view, the petrosal appears rectangular and elongated antero-posteriorly. In most This structure is fragile and is sometimes broken (Loxodonta MNHN.ZM.AC.1956-194, 1932-523)

Cerebral surface

The cerebral surface consists mostly of a very large tegmen tympani. [START_REF] Tassy | L'anatomie cranio-mandibulaire de Gomphotherium angustidens (Cuvier, 1817) (Proboscidea, Mammalia) : données issues du gisement d'En Péjouan (Miocène moyen du Gers, France)[END_REF]. There is a thin separation with the cerebellar surface at the anterior level of the crista partis petrosa. In MNHN.ZM.AC.2008-81 this separation seems to follow the ridge entirely but a closer investigation of the microtomographic slices reveals that this is caused by a fissure. The cerebral surface displays really narrower and shallower grooves as well in most of the specimens.

One groove is slightly more marked and has a trajectory more or less parallel to the groove for the middle meningeal artery. It is closer to the crista partis petrosa, hence we assume that it could be the groove for the superior petrosal sinus.

Tympanic surface

In tympanic view, the petrosal is covered by the tympanic on the skull. A This canal ends in the tympanic cavity delimited by the tympanic bone. This cavity contains the ossicles. On the medial part of the petrosal lies the bulbous promontorium that is oriented mediolaterally and has the overall shape of a teardrop. This structure houses the cochlea and displays two openings.

The most anterior opening is the fenestra vestibuli. It is generally oval and houses the footplate of the stapes when the ossicles are still connected to the skull.

The average value for the stapedial ratio in extant elephants is 1.7. The ratio varies slightly between 1.6 and 1.8 (see Table II and extant sirenians [START_REF] Fischer | Un trait unique de l'oreille des éléphants et des siréniens (Mammalia) : un paradoxe phylogénétique[END_REF]. The perilymphatic foramen is irregular in shape and is always somewhat oblong.

The fenestra vestibuli and the perilymphatic foramen are separated by a rather large ridge called the crista interfenestralis.

Ventrally to the promontorium lies a large process which is the pars mastoidea of the petrosal. The presence of the pars mastoidea in elephants has been somewhat controversial. According to [START_REF] Köstlin | Der Bau des knöchernen Kopfes in den vier Klassen der Wirbelthiere[END_REF] there is no pars mastoidea at all in elephants. However, this portion of the petrosal has been observed by [START_REF] Flower | An introduction to the osetology of the Mammalia[END_REF] which remarks its small size compared to most mammals and its absence on the surface of the skull.

This part of the petrosal was neglected by [START_REF] Buck | A contribution to the anatomy of the elephant's ear[END_REF]1890) The pars mastoidea contains the stylomastoid canal that continues its course through the stylomastoid foramen and which houses the facial nerve in life.

The pars mastoidea contributes to the posterior roof of the canal while the anterior roof is delimited by the tympanic.

In life, the facial nerve originates "from the dorsal aspect of the facial nuclear complex, travels dorsally to the roof of the caudal aspect of the pons, bends laterally In the medial part of the promontorium lies the epitympanic wing which consists of a very thin bony flange.

The medial part of the promontorium is in contact with the tympanic but not fused.

In In several specimens (Elephas MNHN.ZM.AC.2008-81, Loxodonta MNHN.ZM.AC.1932-523, 1861-53, 1950-728 and CEB130168) the portion of the petrosal located medially to the promontorium is inflated.

Ossicles

Some ossicles are still present in the skull of several extant elephants studied (Table II

Vestibular bony labyrinth Ampullae

The ampullae of Loxodonta are less defined than in most other mammals.

While there is a clear demarcation between the ampullar and slender part of the semicircular canals in most mammals, the demarcation is less marked in extant elephants especially when viewed in profile. This feature was already noticed by Benoit et al. (2013b). Some Loxodonta

specimens

Crus commune

The aspect of the crus commune varies between specimens of Loxodonta.

Some specimens display a short and stocky crus commune (MNHN.ZM. AC.1861-53, 1956-194, 1957-465, 1961-69, CEB130168) 53, 1932-523, 1956-194 andCEB130168) display rather lower values (3.57, 3.02, 2.74 and 3.28 respectively) than the thicker specimens (MNHN.ZM. AC.1950AC. -728, 1957AC. -465, 1961AC. -69 and 2008-71) -71) that display higher values for this ratio (3.69, 4.01, 4.77 and 3.90)

Cochlear bony labyrinth

The number of turns of the cochlea is not a constant feature amongst studied specimens of Loxodonta.

MNHN.ZM. AC.1957AC. -465, 1956AC. -194 and 1961-69 -69

Elephas maximus

Four specimens of Elephas were studied including one petrosal removed from a fresh cadaver and still preserving the membranous labyrinth. For each specimen, only one ear was CT-scanned.

Vestibular bony labyrinth Ampullae

The ampullae of As in the bony labyrinth, its apex is located higher than that of the posterior duct.

The slender part of the anterior duct is The overall shape of the lateral semicircular canal differs between specimens of the same genus and even between specimens of the same species.

In Elephas, it is round for every specimen except MNHN.ZM.AC.1904-273. In L.

cyclotis, half of the specimens displays a round lateral canal while the other half displays an oval canal. The shape of this canal is therefore variable and should not be used in phylogenetic analysis.

However, the shape of the two other semicircular canals is constant in extant elephants (the anterior canal is oval and the posterior canal is round in all studied specimens).

The angle formed between the major axis of the anterior semicircular canal and the axis of the crus commune is not constant among specimens of the same genus or of the same species. In The variation is also found at the intraspecific level in L. cyclotis. Hence one must watch out for this when defining character states about the radii of curvature. 194, 1957-465 and 1961-69). Loxodonta This variability is further investigated statistically in Chapter IV.

Intra-individual variability

The

Differences between Elephas and Loxodonta

Even though the bony labyrinths of

Differences between the two African species

A major part of our observations is the difficulty to discriminate petrosal and inner ears of Elephas and Loxodonta. Both genera seem to display similar ear regions.

Moreover, the intra-specific variability of the inner ear is rather strong and it appears to be really difficult to discriminate the two genera using anatomical observations and basic linear measurements. Incidentally, it seems rather impossible to discriminate the two species of Loxodonta using only anatomical characters, especially given the taxonomic proximity of these two species (and difficulty to distinguish their skulls).

An attempt will be made to discriminate both Loxodonta species and the two genera using a geometric morphometrics approach based on 3D labyrinth landmarks in Chapter IV.

Conclusions

We provide here the first comprehensive study of the ear region of extant elephants using CT scan methods.

The anatomy of the petrosal and the bony labyrinth is thoroughly investigated and compared between the three extant species. Moreover, the membranous In perspective, the ontogenetic variability of the petrosal and inner ear characters should be investigated in the future. The taxa sample is here too restricted to conduct such study and the precise age is unavailable for most specimens.

Introduction

The Ocepeia daouiensis [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF] was also performed in this chapter.

The final objective of this chapter is to compare the morphology of the newly investigated taxa with previously documented taxa in order to establish new primary homologies to be tested in a cladistic analysis (Chapter V). and the area of the vestibule is damaged.

Material and methods

Proboscideans

Numidotherium

Numidotherium koholense Jaeger, 1986 was described by Mahboubi et al. (1984[START_REF] Mahboubi | El Kohol (Saharan Atlas, Algeria): a new Eocene mammal locality in Northwestern Africa[END_REF] (Libya) [START_REF] Wight | Paleogene vertebrate fauna and regressive sediments of Dur at Talhah, southern Sirt Basin, Libya[END_REF]. It has been described in a previous work [START_REF] Court | The periotic of Moeritherium (Mammalia, Proboscidea) : homology or homoplasy in the ear region of Tethytheria McKenna[END_REF]. Although this specimen is also highly mineralized, the X-rays of the CTscanner were able to pass through.

However, the microtomographic slices are

Methods

The specimens were CT-scanned in different facilities presented in the main 'Material and methods' section of the thesis (see Table III III.1).

Systematic descriptions

Vestibular bony labyrinth

Ampullae

The ampullae of Ocepeia are welldefined and inflated (Fig III.1). They are smooth and display no ridges.

Crus commune

The crus commune is elongated and displays no marked basal thickening.

It is smooth and displays no ridges. The average section radius of the crus commune of Ocepeia is small (0.30 mm) and its length is approximately 1.75 mm.

Therefore, the crus commune thickness ratio is low (17.35). The anterior and posterior semicircular canals meet high (at 75% of the height of the anterior canal)

and the crus commune is not inclined.

Semicircular canals

The anterior semicircular canal is round. The central streamline length of this canal is 6.87 mm (Table III.2) and its average section radius is 0.15 mm.

Therefore, the thickness ratio of this canal is 2.22 making it quite slender. The anterior canal is the biggest in Ocepeia (the radius of curvature is 1.64).

The posterior semicircular canal is round. The central streamline length is similar to the value found for the anterior canal although slightly longer (7.49 mm).

The average section radius is very similar to the anterior one (0.16 mm). Hence the thickness ratio of the posterior canal The radius of curvature of the lateral canal is 1.24.

The angle between the anterior There is indeed a partial fusion of the bony lateral canal with the posterior ampulla.

All three semicircular canals display a slight undulation. No ridges were observed on the semicircular canals.

Cochlear bony labyrinth

The number of turns of the cochlea

Unnamed Embrithopoda from the Ypresian of Morocco

The isolated petrosal of a yet unpublished representative of the order Embrithopoda (collection number PM53) has been CT-scanned and described for comparisons with proboscideans. Only a fragment of this petrosal has been preserved (the cochlea is almost completely broken) hence the total volume of its inner ear remains unknown.

Petrosal

The petrosal is very incomplete and damaged. In cerebellar view, the internal auditory meatus is shattered but its No other anatomical features can be seen in the other views.

Vestibular bony labyrinth

Ampullae

The ampullae of PM53 are welldefined and inflated (Fig III .2). They are smooth and display neither ridges nor bumps.

Crus commune

The crus commune is elongated and displays no marked basal thickening.

It is smooth and displays no ridges. The average section radius of the crus commune of PM53 is 0.53 mm and its length is approximately 3.92 mm.

Therefore PM53 has the crus commune

with the lowest thickness ratio of our sample (13.63). The anterior and posterior semicircular canals meet very high (at more than 85% of the anterior canal height) and the crus commune is not inclined. In cross-section, the canals appear to be circular with no particular flattening. The slender part of the lateral semicircular canal is connected to the vestibule at a quite high position. This is illustrated by a partial fusion of the bony lateral canal with the posterior ampulla, as in Ocepeia.

No ridges nor marked undulations were observed on the semicircular canals.

Cochlear bony labyrinth

Little can be described about the cochlea of this specimen because only a small fraction of this region is preserved.

The number of turns is unknown but it displays more than one and a half turn.

Indeed, traces of a second cochlear turn have been reconstructed but we cannot know if this second turn is complete. The lamina secundaria is present in PM53 as it is preserved on the part of the first turn that we were able to reconstruct.

Proboscideans

Numidotherium koholense

The petrosal and bony labyrinth of

Vestibular bony labyrinth

Ampullae

The ampullae are well marked as in the unlabeled specimen studied in Benoit et al. (2013b). There are no ridges observed on the ampullae (Fig III .3).

Crus commune

The crus commune is elongated with no marked basal thickening. It does not display any ossification irregularities as in some specimens of extant elephants.

The crus commune is thin with an aspect ratio of 14.96. Its central streamline length

Semicircular canals

The anterior semicircular canal is round. The central streamline length of this canal is 13.89 mm and its average section radius is 0.34 mm.

Therefore, the thickness ratio of this canal is 2.47. The length that we found is longer than the measure given by Benoit et al.

(2013b) (12.17 mm) for the other specimen. However, this could be due to the difference of protocol used to calculate the length. The anterior canal is the largest canal with a radius of curvature of 3.52. Again, the radius of curvature is larger in our specimen but this could be together [START_REF] Gray | The Labyrinth of Animals[END_REF][START_REF] Gray | The Labyrinth of Animals[END_REF][START_REF] David | Le système des canaux semi-circulaires des archosaures : anatomie, morphométrie, morphologie fonctionnelle, évolution[END_REF].

The fusion occurring in

Cochlear bony labyrinth

The cochlear bony labyrinth of Numidotherium was previously described by [START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF] and Benoit et al. (2013b).

Here, we will compare the endocast of (2013b) for the unlabeled specimen (44%).

Moeritherium lyonsi

The periotic of Moeritherium was already described in Court (1994) using a

specimen from the collection of the London Natural History Museum (NHMUK 68436). The inner ear was partially described in [START_REF] Tassy | Le crâne de Moeritherium (Proboscidea, Mammalia) de l'Eocène de Dor El Talha (Libye) et le problème de la classification phylogénétique du genre dans les Tethytheria McKenna[END_REF] in a specimen that bears a partial natural cast of the labyrinth. We tried to scan this specimen but it was too dense to obtain legible tomographies. On the other hand, the specimen described by [START_REF] Court | The periotic of Moeritherium (Mammalia, Proboscidea) : homology or homoplasy in the ear region of Tethytheria McKenna[END_REF] has been CT-scanned successfully. However, the bony labyrinth is not complete and it is filled with sediment. The specimen is also The poor resolution of the CT scans prevents us from discussing the eventual ossification irregularities of the ampullae.

The ampullae are not preserved at all in SMNS 47789-90.

Crus commune

The

Cochlear bony labyrinth

The cochlear part and the area of the vestibule are not preserved at all in SMNS 47789-90. The cochlea is not well preserved as well. It completes at least one and a half turns in specimen NHMUK 68436 (Fig III .4G). In the specimen described in [START_REF] Tassy | Le crâne de Moeritherium (Proboscidea, Mammalia) de l'Eocène de Dor El Talha (Libye) et le problème de la classification phylogénétique du genre dans les Tethytheria McKenna[END_REF], the cochlea completes 2.25 turns. There could be an apical lacuna in specimen NHMUK 68436 but it is hard to tell. In all cases, the modiolus is rather loose. The poor contrast prevents us from observing the presence of a lamina secundaria. given by the author.

Prodeinotherium bavaricum

Petrosal

The petrosal of the only specimen that is probably a Prodeinotherium The crista partis petrosa is not sharp.

There is no trace of a subarcuate fossa.

The cerebral surface consists mostly of the tegmen tympani. The groove for the middle meningeal artery is not visible. In tympanic view, the tegmen tympani appears shorter and more bulbous than in elephantimorphs. The promontorium is damaged but it appears to be moderately bulbous. The fenestra vestibuli is not preserved (if so, it is heavily broken). The perilymphatic foramen is broken as well but its location is still visible on the reconstruction (Fig III .6A and 6B). There is no trace of a cochlear canaliculus, hence the unique perilymphatic foramen seems to be retained during ontogeny as in extant elephants [START_REF] Fischer | Un trait unique de l'oreille des éléphants et des siréniens (Mammalia) : un paradoxe phylogénétique[END_REF]

Mammut americanum

Petrosal

Crus commune

The crus commune is elongated and displays no marked basal thickening.

Semicircular canals

The anterior semicircular canal is oval in both FM14293-A and FM14293-B.

While the major axis of the canal forms an angle of 27° with the crus commune in

Gomphotherium angustidens

Three specimens of Gomphotherium angustidens were CT-scanned. First, the basicranial region of MNHN skull specimens SEP18 and SEP38 was scanned.

The contrast and resolution of the microtomographic sections obtained for SEP18 were so poor that the inner ears of this specimen could not be segmented. On the contrary, both inner ears of SEP38

were complete and contrasted enough to be segmented. However, the resolution was not good because of the great size of the specimen. Hence, an isolated petrosal of another specimen of Gomphotherium angustidens from the collections of the Natural History Museum of Toulouse (Cbar coll.V 2) was scanned and entirely segmented.

Petrosal

The petrosal of Gomphotherium was previously described by Tassy (2013) so we will not describe it in details here.

Inner ear

The total volume of the inner ear is 814 mm 3 in MNHN.F.SEP38 (average value of the left and right inner ears) and 988 mm 3 for Cbar coll.V 2.

Vestibular bony labyrinth

Ampullae

The ampullae of Gomphotherium angustidens appear less defined like most proboscideans. There is no clear ampullar ridge on any studied specimens (Fig III .12).

Crus commune

The crus commune is elongated in all studied specimens of Gomphotherium.

There is a huge basal thickening of the

Cuvieronius sp.

Petrosal

The overall aspect of the petrosal is similar to the elephantimorphs in general

Crus commune

The crus commune is elongated

Inner ear

Vestibular bony labyrinth

Ampullae

The ampullae of Stegomastodon appear poorly defined as in most modern proboscideans. There is no clear ampullar ridge on any of the ears (Fig III.17).

However this feature is impossible to observe in the right ear given their condition.

Crus commune

The There is no trace of ridges on the canals of Stegomastodon. In both ears, the semicircular canals display undulations.

Cochlear bony labyrinth

The There is no trace of a subarcuate fossa and the internal auditory meatus is not visible.

Vestibular bony labyrinth

Ampullae

The ampullae of Platybelodon are poorly defined (Fig III.18). The poor level of contrast and therefore the rather imprecise segmentation of the labyrinth prevents us from observing the presence of ridges on the ampullae.

Crus commune

The crus commune is stocky and displays a marked basal thickening.

However, it is not pyramidal as in 190

III

Cochlear bony labyrinth

The number of turns of the cochlea Therefore, the value for the thickness ratio is the same as for the anterior canal (3.51).

The radius of curvature of the posterior canal is 7.48 which is very large.

The lateral semicircular canal is quite round in both ears of FM18632.

Compared to the other semicircular canals, the lateral canal is the shortest with a length of 15.17 The aspect ratio of the cochlea is 0.5, making it more conical than in extant elephants.

Mammuthus

Two

Crus commune

The crus commune is stocky in both taxa, with a slight basal thickening.

It is smooth in

Comparisons

Comparative charts in different views are given in Appendices 5-10.

Petrosal

Subarcuate fossa

The subarcuate fossa is a depression that holds a parafloccular lobe of the cerebellum in life. Its depth and even its presence is variable among mammals. The fossa is very deep in nonplacental eutherian mammals such as the zhelestidae Kulbeckia [START_REF] Ekdale | Petrosal bones of placental mammals from the Late Cretaceous of Uzbekistan[END_REF].

It seems to be the general condition of mammals. The early afrotherian Ocepeia exhibits a very deep and conical subarcuate fossa [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF].

In proboscideans, the early Eritherium displays a very deep fossa as well but its shape is somewhat different from that of Ocepeia as it is more spherical.

Phosphatherium, on the other hand, exhibits a shallow fossa. Moeritherium and later proboscideans have completely lost the subarcuate fossa. A shallow depression might be retained in some proboscidean taxa such as Moeritherium [START_REF] Court | The periotic of Moeritherium (Mammalia, Proboscidea) : homology or homoplasy in the ear region of Tethytheria McKenna[END_REF]

Internal auditory meatus

The

Stapedial ratio

The stapedial ratio of the fenestra vestibuli is a variable character in proboscideans. In Anancus arvernensis, for example, it varies between 1.6 and 1.8. In

Elephas maximus, it varies between 1.52 and 1.83. In [START_REF] Ekdale | Morphological variation in the ear region of Pleistocene Elephantimorpha (Mammalia, Proboscidea) from Central Texas[END_REF], the ratio varies Embrithopoda, the massive Arsinoitherium displays a unique perilymphatic foramen [START_REF] Court | Periotic anatomy of Arsinoitherium (Mammalia, Embrithopoda) and its phylogenetic implications[END_REF], but this character is impossible to observe in the early embrithopod PM53, as it is broken at the level of the vestibule. In Sirenia, the perilymphatic foramen is present only in extant genera (Dugong, Trichechus) but the foramen is separated in early sirenians such as Prorastomus and the specimen from Chambi (Benoit et al. 2013a). Finally, the unique perilymphatic foramen is also present in the gray whale

Eschrichtius robustus [START_REF] Geisler | The petrosal and inner ear of Herpetocetus sp. (Mammalia: Cetacea) and their implications for the phylogeny and hearing of archaic mysticetes[END_REF]. As far as we know, no other mammal taxa than those cited here display this feature.

Inner ear

Definition of the ampullae

The ampulla of a semicircular canal This character does not display intraspecific variability and is quite clear to define. Therefore it is included in our cladistic analysis.

Overall shape of the crus commune

The overall shape of the crus commune (slender or stockier) is rather These two states of crus morphology could be significant phylogenetically;

however the study of several specimens of extant elephants showed that this character is also variable at intra-generic and intra-specific levels. Hence, we decided not to include this character in the phylogenetic analysis performed in Chapter V.

Meeting point of the anterior and posterior canals

The height of the meeting point of the anterior and posterior canals is

Thickness ratio of the crus commune

The thickness ratio of the crus commune is based on two measurements given by the ARIADNE add-on using 3D landmarks (the average section radius of the crus commune and the length of the crus commune). Hence, it was possible to obtain this ratio only for specimens that Gomphotherium specimens. In this regard, the pyramidal shape seems to be a good diagnostic character of Gomphotherium.

Inclination of the crus commune

In general, the crus commune is completely straight in mammals.

III -Anatomy of the ear region of fossil proboscideans However, we identified several specimens displaying a rather inclined crus commune.

The inclination is always towards the anterior semicircular canal in our sample. Additionally, Anancus NMNHS.FM2991B displays a particularly marked inclination.

The inclination does not seem to be caused by a taphonomic process as it is observed in both right and left ears in Mammuthus columbi and Stegodon.

However, it seems to be variable inside the same species as it is not seen in some Anancus specimens.

Overall shape of the anterior canal

In early proboscideans such as as well as in the fossil hyracoid Seggeurius [START_REF] Benoit | New material of Seggeurius amourensis (Paenungulata, Hyracoidea), including a partial skull with intact basicranium[END_REF]). However, it is oval in Tenrec. Even though there is some variability in Gomphotherium, the character seems quite constant intraspecifically. Therefore, it is be interesting to include this character in a cladistics analysis.

Overall shape of the posterior canal

The

Relative size of the canals

The radii of curvature of the semicircular canals are size-related

Flattening of the canals

In most mammals, the crosssection of the semicircular canals is circular and the canals have a cylindrical

General thickness of the canals

The semicircular canal thickness is variable among mammals and particularly among afrotherians and proboscideans.

This feature can be assessed by the naked eye but we used a more quantitative approach by using the average thickness

Insertion point of the lateral canal into the vestibule

The point of entry of the lateral canal into the vestibule is not subject to In the early afrotherian Ocepeia, the cochlea represents around two thirds of the total volume of the bony labyrinth.

Aspect ratio of the cochlea

The protocol used to calculate the aspect ratio of the cochlea is the same

Apical lacuna

The presence of the apical lacuna is not a constant character. It is variable in Ocepeia, a small apical lacuna is present in both ears [START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF].

Lamina secundaria

The secondary bony lamina (or

lamina

Vestibulo-cochlear angle

The protocol used to measure the vestibulo-cochlear angle comes from

Conclusion

The This study is preliminary and based on the data that were possible to get during the PhD thesis. We expect to extend the sampling and the study in the future.

Methods

Data preparation

The specimens were segmented However, the software that we used to conduct the geometric morphometrics analyses (MORPHOTOOLS) requires equally composed landmark sets. Hence, we used the software MATHEMATICA to resample our landmark sets.

Analyses

The landmark sets were then analyzed with the interactive software package MORPHOTOOLS [START_REF] Specht | Spherical surface parameterization and its application to geometric morphometric analysis of the braincase[END_REF][START_REF] Specht | Visualizing shape transformation between chimpanzee and human braincases[END_REF][START_REF] Lebrun | Evolution and development of the strepsirrhine primate skull[END_REF][START_REF] Lebrun | Deep evolutionary roots of strepsirrhine primate labyrinthine morphology[END_REF]. First, we applied a sliding semilandmark algorithm given by the software until stable mean shape was obtained. This step allows removing information derived from the arbitrary spacing of semilandmarks along these curves [START_REF] Billet | Morphological diversity of the bony labyrinth (inner ear) in extant xenarthrans and its relation to phylogeny[END_REF][START_REF] Gunz | The mammalian bony labyrinth reconsidered, introducing a comprehensive geometric morphometric approach[END_REF].

IV IV -Geometric morphometrics study of the bony labyrinths of proboscideans and afrotherians This correlates with a small and tightly coiled cochlea. The particularly high number of turns of the specimen (3.5) does not seem to influence strongly the morphospace. In fact, the number of turns . "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Results

Analysis of the

IV -Geometric morphometrics study of the bony labyrinths of proboscideans and afrotherians

PC3 (11%)

The .1961-69, 1956-194, 1957-465) are located towards the positive extremity of PC1.

Both Gomphotherium specimens plot together along PC1 and PC2.

Anancus genus

It is noted that the seven specimens of Anancus form a distinct cluster explained mostly by PC2 (positive) and PC3 (negative). This correlates with acute angles between the semicircular canals in general.

Impact of the addition of cochlear landmarks

The analysis restricted to semicircular canals permits to include a larger number of specimens into the analysis. On the other hand, the comparison of the results found in the two analyses permits to discuss about the importance of the cochlear morphology in the comparative anatomy of the afrotherian bony labyrinths. There are significant differences between the two sets of analyses: the principal components do not explain the same amount of the total variation (see Table IV.2) and some clusters are better defined in one analysis, while they are less defined in the other.

These changes are greatly influenced by the presence/absence of the cochlea in the analysis but this can also be influenced by the additional taxa analyses restricted to the canals. Hence, we will first compare the two analyses performed on extant elephants. Indeed, while the first analysis (E1) includes the cochlea, the second (E2) is performed only on semicircular canals.

However, the taxonomic sample is the same between the two analyses; hence the differences observed between the results are only due to the addition of cochlear landmarks into the dataset.

Extant elephants (E1 and E2)

In both analyses E1 and E2, the

Afrotheria (A1 and A2)

In both the analyses A1 and A2, the proboscidean and afrotherian clusters overlap. However, in both analyses, the elephantimorphs form a distinct cluster.

Elephantimorphs are better discriminated Together with the other known procaviid species (Benoit, 2013), it indicates that the entire Procaviidae family is extremely derived, by contrast to the general postcranial construction, but in accordance with the morphology of the feet and hands [START_REF] Gheerbrant | Première description du squelette d'un hyracoïde paléogène: Saghatherium antiquum de l'Oligocène inférieur de Jebel al Hasawnah[END_REF].

Tenrec and Elephantulus probably display labyrinths closer to the hypothetical ancestral morphotype of the Afrotheria.

Only fossil species of sirenians are included in our analyses. Their peculiar labyrinth morphology (Benoit, 2013) makes it likely that the modern sirenians would exhibit similar levels of specialization, as observed in Procavia.

This hypothesis remains to be checked with the inclusion of the modern sirenians in the analysis.

Differences between the bony labyrinth of Arsinoitherium and elephants

A surprising result of the analysis This contrasts with previous conclusions that the ear region of Arsinoitherium is very similar to the ear of extant elephants.

Such convergences were observed in the petrosal anatomy [START_REF] Court | Periotic anatomy of Arsinoitherium (Mammalia, Embrithopoda) and its phylogenetic implications[END_REF] and in the bony labyrinth (Benoit et al. 2013b). In the

Loxodonta cyclotis VS Loxodonta africana

At that time, we were not able to convincingly discriminate the African bush elephants (Loxodonta africana) from the African forest elephants (Loxodonta cyclotis). This is not surprising as the

Conclusion

Our geometric morphometric analyses based on 3D landmarks of the labyrinth of proboscideans and other

afrotherians help to answer to the three main questions investigated in this chapter.

1. We find some overlap between some proboscideans and afrotherians. The The regressions showed that the majority of the typical elephant morphology is not influenced by size. This is particularly true for the whole labyrinth.

However, the morphology of the canals only displays a stronger (though moderate) influence of size.

To conclude, we were able to The phylogenetic message carried by the ear region in this group has been thoroughly investigated before (Benoit, 2013). We only explore here the impact of new characters and several new or recently described afrotherian taxa (the Moroccan embrithopod, Ocepeia, proboscideans) in the evolutionary hypotheses about the ear region.

Material and methods

As previously said, two sets of analyses were performed, one restricted to the Proboscidea and one extended to the Afrotheria. Taxa samples and methods for each of these two sets are detailed in this section.

Numidotherium and

Moeritherium were described in [START_REF] Court | Anatomy of the periotic bone in the Eocene Proboscidean Numidotherium koholense : An example of parallel evolution in the inner ear of tethytheres[END_REF], [START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF], [START_REF] Court | The periotic of Moeritherium (Mammalia, Proboscidea) : homology or homoplasy in the ear region of Tethytheria McKenna[END_REF] and Benoit et al. (2013b). New specimens of these two taxa were studied here and used to fill the matrix. There was some information about the petrosal of

Afrotheria

The second set of analyses extends Representatives of the Afrosoricida and the Tubulidentata are not included in the analysis (although Plesiorycteropus is believed to be included in Tubulidentata by some authors).

Methods

Cladistic analysis performed on the Proboscidea

The cladistic analysis performed on Proboscidea was carried out using the software PAUP 3.3.1 [START_REF] Swofford | PAUP: Phylogenetic Analysis Using Parsimony[END_REF]. The analysis is based on 32 ear region characters: 12 petrosal characters and 20 bony labyrinth characters. The complete list of characters is given in Appendix 23.

Details about the characters are given in the following section of this chapter (section 3, 'Characters'). In this section, the states of the characters are given as well as illustrations of each state. Details about the coding method and choices are also given as well as the distribution of the characters states within Proboscidea.

Among the 32 characters, six have more than two states. These multi-state characters were all treated as ordered, as we consider them to correspond to morphological clines. In the analysis restricted to the Proboscidea, eight characters are not informative (4, 6, 8, 14, 25, 26, 27 and 30). Ocepeia and Protungulatum are used as outgroups. We performed a heuristic search and all characters were equally weighted. The matrix is given in Appendix 24.

V -Evolution of the ear region characters within the Proboscidea and the Afrotheria Ocepeia), but these states related to its shape are not discriminated in our study.

Several afrotherians (e.g. Phosphatherium) display a more superficial fossa (1). In this state (1), the fossa depth is clearly more moderate than in state (0), but the outlines of the fossa remain well distinct by contrast to state (2). In state ( 2

0 0 0 0 0 0 1 1 ? 1 1 1 1 1 1 1 1 1 1

287

V -Evolution of the ear region characters within the Proboscidea and the Afrotheria

Perilymphatic foramen: (0) divided into the fenestra cochleae and the aquaeductus cochleae during ontogeny, (1) retained in adults

This character was used in previous analyses [START_REF] Court | Periotic anatomy of Arsinoitherium (Mammalia, Embrithopoda) and its phylogenetic implications[END_REF]Benoit et al. 2013b: character 16). The aquaeductus cochleae

0 0 0 0 0 0 1 1 ? 1 1 1 ? 1 1 1 1 1 1

288

V -Evolution of the ear region characters within the Proboscidea and the Afrotheria

Mastoid apophysis: (0) visible on the skull laterally, (1) amastoidy

The mastoid apophysis is a bony prominence that is generally apparent on the skull, at the postero-lateral corner, between the exoccipital and the squamosal [START_REF] Gheerbrant | Nouvelles données sur Phosphatherium escuilliei (Mammalia, Proboscidea) de l'Eocène inférieur du Maroc, apports à la phylogénie des Proboscidea et des ongulés lophodontes[END_REF]

1 0 ? 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

289

V -Evolution of the ear region characters within the Proboscidea and the Afrotheria

Petrosal pneumatization: (0) absent, (1) present

The petrosal of some mammals display bony air cells: this feature is called pneumatization. The role of the pneumatization can be functional (e.g.

294

V -Evolution of the ear region characters within the Proboscidea and the Afrotheria

Petromastoid canal: (0) absent, (1) present

The petromastoid canal is a discrete canal that lies at the bottom of the subarcuate fossa. It carries the subarcuate artery, vein and nerves in humans [START_REF] Gannon | The subarcuate fossa and cerebellum of extant primates: Comparative study of a skull-brain interface[END_REF]. The absence of this canal is coded 0 while its presence is

296

V -Evolution of the ear region characters within the Proboscidea and the Afrotheria

Transpromontory sulcus: (0) absent, (1) present

This character directly comes from Benoit et al. (2013b;character 11) and is modified from [START_REF] Wible | Transformations in the extracranial course of the internal carotid artery in mammalian phylogeny[END_REF]. The coding is left unchanged from Benoit et al. (2013b).

The internal carotid artery generally runs in the petrosal region of mammals [START_REF] Wible | Transformations in the extracranial course of the internal carotid artery in mammalian phylogeny[END_REF]. In some taxa, the artery runs on the surface of the promontorium, leaving a groove called the transpromontory sulcus We assume that the sulcus observed in Phosphatherium is instead more likely the groove for the inferior petrosal sinus. Hence, the character is only applicable on specimens for which we have a 3D reconstruction of the bony labyrinth. It is not possible to code specimens only illustrated in the literature. To do so, the character would have to be modified and be less precise, not using the thickness ratio. This ratio was previously not used in cladistic analyses.

0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1

306

V -Evolution of the ear region characters within the Proboscidea and the Afrotheria

General thickness of the semicircular canals: (0) slender canals, thickness ratio < 3, (1) thick canals, thickness ratio >3

The thickness of the bony semicircular canals varies among mammals in general, and in particular among proboscideans. As for the crus commune thickness (character 15), it can be tricky to evaluate the degree of thickness of the canals and to translate it into a phylogenetic character. Thus we used the same method as for character 15, except that we instead used the general thickness ratio of the canals. This ratio is the mean of the average thickness ratios of each canal, which is the ratio of Finally, if there is no contact at all between the canals, the state is 2. Specimens displaying a more obtuse angle (between 90° and 142°) are coded 1.

Illustrations of this character

Specimens with a particularly large angle (superior to 142°) are coded 2.

Illustrations of the character states are given in Fig V .30. This character is tested here for the first time on proboscideans.

In our studied material sample,

Cuvieronius, Palaeoloxodon and

Mammuthus columbi do not preserve the cochlea; the coding of this character is undetermined for these taxa and for the taxa that we did not segment ourselves (e.g. Protungulatum). Schmitt & Gheerbrant, 2016). However, the consistency index is defective and strongly influenced by other factors than the homoplasy [START_REF] Darlu | La reconstruction phylogénétique[END_REF]. For instance, the index tends to be higher in datasets that contains a small number of taxa which partially explains the very high consistency index found in the preliminary analysis conducted in Chapter I. To address that problem, we chose instead to use the retention index in the rest of the chapter as a measurement of the homoplasy. The retention index measures the opposite of the distortion; the higher the index, the lower the homoplasy (RI; Farris, 1989aFarris, , 1989b)). Here, the index value (RI = 0.628) is higher than the This clade was recovered in previous studies [START_REF] Court | A new species of Numidotherium (Mammalia : Proboscidea) from the Eocene of Libya and the early phylogeny of the Proboscidea[END_REF][START_REF] Delmer | Les premières phases de différenciation des proboscidiens (Tethytheria, Mammalia): le rôle du Barytherium grave de Libye[END_REF][START_REF] Gheerbrant | L'origine et l'évolution des éléphants[END_REF]Schmitt & Gheerbrant, 2016). It is supported by Therefore, we cannot discuss the evolution of these characters among the main proboscidean taxa. For this reason, we studied the distribution of the ear characters of our proboscidean sample taxa in a mapped consensual tree (for the method, see § 2.2.2.).

Internal auditory meatus orientation

Hiatus Fallopii

Prootic sinus

The prootic sinus is absent in all studied proboscideans. Therefore, the character is constant in this mammal order. This character is only useful in analyses performed on Afrotheria or Eutheria. Therefore, the acquisition of the transpromontory sulcus is considered an autapomorphy of this taxon. However, it should be noticed that this sulcus is never really deep and that its absence does not necessarily mean that there were no blood vessels running on the promontorium, only that these vessels did not excavate the bony surface of the petrosal. of Ocepeia is considered thick with our coding protocol but its ratio (17.4) is close to the limit between states [START_REF] Benoit | lateral semicircular canal[END_REF]. In the proboscideans, however, the crus commune seems to be primitively slender as early taxa display a very small ratio (Eritherium, Phosphatherium, Numidotherium). The thickening of the crus commune in later proboscideans is a synapomorphy that appeared either in node 5 or 6 (it was not possible to calculate the ratio in Moeritherium).

Crista falciformis

Definition of the ampullae

Gomphotherium display polymorphism as the CBar coll. V2 specimen ratio is under 15. V -Evolution of the ear region characters within the Proboscidea and the Afrotheria

Meeting point of the anterior and posterior canals into the crus commune

Posterior expansion of the lateral canal

The lateral canal posterior expansion is absent in all studied proboscidean. This character is only useful in analyses performed on Afrotheria or Eutheria. The aspect ratio of the cochlea is inferior to 0.6 in all studied proboscideans.

Aspect ratio of the cochlea

The cochlea is not preserved in studied specimens of Cuvieronius, Palaeoloxodon and

Mammuthus columbi. In

Moeritherium, the cochlea is not sufficiently preserved to calculate a precise aspect ratio. Finally, the roof of the promontorium is damaged in Phosphatherium which prevents from calculating the aspect ratio as well.

However, given its morphology, the cochlea of Phosphatherium is likely to display a ratio superior to 0.6, as Ocepeia.

The evolution of this character is therefore ambiguous (Fig V .56).

V -Evolution of the ear region characters within the Proboscidea and the Afrotheria

Number of turns of the cochlea

This character is constant in proboscideans, at least with the coding that was defined.

The character is therefore only useful in analyses performed on Afrotheria or Eutheria. Early proboscideans exhibit a lamina secundaria as well. In Eritherium, the lamina is quite deep and marked. The lamina is weaker in Phosphatherium but still present. In Numidotherium, it has been observed in some specimens [START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF] but the lamina is absent on others.

Lamina secundaria

Moreover, the information is missing in Moeritherium. Therefore, the loss of the In Phosphatherium, the roof of the promontorium is broken, therefore, the apical turn is not entirely preserved and the observation of its center of rotation is not possible. In Moeritherium, the cochlea

Conclusion

In this chapter, the evolution of the The integration of nervous messages transmitted by the six semicircular ducts allows the brain to interpret the direction and amplitude of head rotations.

Semicircular ducts biomechanics

Biomechanics of the semicircular ducts can be compared to that of a torsion pendulum. Hence the mechanics of this system can be summarized with this equation: Conversely, a rotation of the head around the axis defined by the vector 𝐺𝐺 𝑘𝑘 ����⃗ will induce a maximal response of the duct.

Mass parameter (M k )

To calculate the mass parameter, the equation is (following Rabbitt et al.

Cupula stiffness parameter (K k )

To calculate this parameter, the equation is (following [START_REF] Rabbitt | Biomechanics of the semicircular canals and otolith organs[END_REF]:

𝐾𝐾 𝐾𝐾 = 𝜆𝜆 𝛾𝛾𝑘𝑘 • 𝛾𝛾 • 𝑡𝑡 𝑘𝑘 𝐴𝐴𝐴𝐴 𝑘𝑘 2
In this equation, λ γk represents the cupula deformation factor, γ represents the shear stress factor, which is a physiological parameter affecting the deformation profile of the cupula, t k represents the average thickness of the cupula and Ac represents the average section area of the cupula.

Inertial forcing parameter (𝐺𝐺 𝑘𝑘 ����⃗ )

To calculate this parameter, the equation is (following [START_REF] Rabbitt | Biomechanics of the semicircular canals and otolith organs[END_REF]):

𝐺𝐺 𝑘𝑘 ����⃗ = 2𝜌𝜌Λ � �⃗
In this equation, Λ � �⃗ corresponds to the area enclosed by the duct torus, as projected into the maximal response plane.

Functional parameters

Semicircular ducts are governed by several functional parameters. In this chapter, we will focus on three

Short time constant (T 2 )

The short-time constant represents the time taken by the cupula to be maximally displaced after the stimulus. Natural frequency (ω 0 )

The natural frequency (ω 0 ) is the frequency for which the deflection of the cupula is in phase with angular velocity.

The higher the natural frequency, the higher the tendency of the animal to experience frequent head motion. It can be calculated with this equation:

𝜔𝜔 0𝑘𝑘 = 1 2𝜋𝜋 * � 𝐾𝐾 𝑘𝑘 𝑀𝑀 𝑘𝑘
K k is a parameter defined by the cupula which is a membranous feature that cannot be inferred using the bony labyrinth only. As previously said, M k is greatly influenced by the average crosssectional area of the duct. Hence, meticulously-segmented membranous labyrinth 3D models are crucial to calculate this parameter.

Sensitivity (or velocity gain, 𝑉𝑉𝐺𝐺𝑉𝑉 𝑘𝑘 ����������⃗ )

The sensitivity (or velocity gain,

Axes of rotation

The vertical semicircular ducts do not detect the same types of rotation than the lateral duct. This is due to the

Objectives

The

Results

Functional capacities of extant afrotherians

Comparisons of the functional parameters of the semicircular duct system of three afrotherian mammals (Elephas maximus, Procavia capensis and Elephantulus) allow us to discuss differences in the context of variation in animal size and ecology.

Raw values

Raw -or effective -values of the functional parameters calculated with the software ARIADNE are given in Table VI.2.

Among these values, we will discuss three major functional parameters: the shorttime constant (T 2 ), the natural frequency (ω 0 ) and the sensitivity (or velocity gain, VGs).

Short time constant (T 2 )

The short-time constant is particularly low in Elephantulus with little to no difference between its ducts (1.2 ms in vertical ducts and 1.3 ms in the lateral duct). In comparison, Procavia displays an approximately 1.5 times higher short-time constant with still no particular differences between ducts (1.9 ms in the anterior duct, 2.1 ms in the posterior duct and 2.0 ms in the lateral duct).

Short time constant (T 2 )

The short time constant of the mammalian ancestral morphotype is more or less constant between anterior and posterior ducts. It is slightly lower for the lateral duct, meaning that the semicircular duct system generally responds slightly faster in yaw than in pitch and roll in mammals.

The short time constant of the vertical ducts of Elephantulus are similar to the mammalian ancestral morphotype although slightly higher. This implies that when the effect of the size is eliminated, the response speed of the semicircular duct system of Elephantulus is in the mammalian middle range but slightly

Natural frequency (ω 0 )

The natural frequency of the mammalian ancestral morphotype is rather similar between all its ducts, which means that, in general, mammals tend to display similar frequencies of head motion in all axes.

Sensitivity (or velocity gain, VGs)

The V/L ratio of the mammalian In Elephantulus, the V/L ratio is also close to 1 (0. to its small size.

Functional inferences on fossil proboscideans and afrotherians

Raw estimated functional parameters

As previously said, size have a high impact on functional parameters. Species This suggests that, if we eliminate the effect of size, they experience relatively higher angular velocities for yaw rotations.

Hence we can assume that either VI -The semicircular duct system of the Proboscidea and the Afrotheria

Discussion

Agility

Agility can be defined as the capacity to rapidly change directions [START_REF] David | Le système des canaux semi-circulaires des archosaures : anatomie, morphométrie, morphologie fonctionnelle, évolution[END_REF]. This is controlled by angular velocity during head motion, which is detected by the semicircular ducts. Hence, the information given by the morphology of semicircular ducts (inferred from that of the canals) provides insights on the agility of extinct mammals. Agility is inversely proportional to the sensitivity (VGs).

Indeed, the more an animal is sensitive, the faster its ciliae attain their maximum of deflection, which leads to saturation of the system [START_REF] David | Le système des canaux semi-circulaires des archosaures : anatomie, morphométrie, morphologie fonctionnelle, évolution[END_REF]. On the other hand, the more an animal is sensitive, the more precise it is to detect small angular velocities. Therefore, adaptation of the sensitivity in mammals is a trade-off. If the system is adapted to high sensitivities (VGs), the animal will be able to detect precise small angular velocities. However, the semicircular duct system will be saturated more rapidly and the animal will not be able to change directions rapidly (i.e. the animal will not be very agile).

Conversely, if the system is adapted to low sensitivities (VGs), the animal will be very agile but will not be able to detect small angular velocities. To evaluate the agility of terrestrial vertebrates, the most interesting sensitivity values are that of the lateral duct. Indeed, terrestrial vertebrates move predominantly in two (horizontal) dimensions contrary to flying vertebrates which move in three dimensions [START_REF] Cox | Semicircular canals and agility: the influence of size and shape measures[END_REF].

It has been pointed out that

Elephantulus displays a very low effective sensitivity for the lateral duct, which means that it is very agile. However, its body-mass free lateral duct sensitivity is particularly elevated compared to other afrotherians and even the mammalian morphotype (Table VI .3). This suggests that the morphology of the Elephantulus lateral duct is not particularly adapted to agility if the effect of size is eliminated.

This could be easily explained by the lack of predators that have a similar size as

Elephantulus. The very small size of Elephantulus (it weighs only 56.5 g) already naturally confers it a great agility (hence the very low effective sensitivity).

Therefore, there must thus be less selection pressure onto the vestibular system of Elephantulus to decrease its sensitivity because its predators already have the disadvantage to be larger (and thus naturally less agile) while [START_REF] Heffner | Hearing in the elephant (Elephas maximus): Absolute sensitivity, frequency discrimination, and sound localization[END_REF] and it was documented that they are able to produce sounds below the human auditory range (i.e.

infrasounds, inferior to 20 Hz; [START_REF] Payne | Infrasonic calls of the Asian elephant (Elephas maximus)[END_REF]). The infrasound vocalization has been related to spatial coordination and mating [START_REF] Poole | The social contexts of some very low frequency calls of African elephants[END_REF]) and allows the elephant to communicate at long distances [START_REF] Langbauer | African elephants respond to distant playbacks of low-frequency conspecific calls[END_REF]). The distance range in which the calls can be perceived by elephants (i.e. calling area) depends on topographic and atmospheric factors; hence, the calling area varies during the day and between seasons (Larom et al. 1997a;1997b). The infrasounds can be perceived at 2.

Features observed to infer auditory capacities

There are several features of the cochlea that can inform us about the auditory capacities of fossil species.

Observations of these characters can give some clues about the tendency of the animal capacity to hear high-frequency

407

VII -Preliminary considerations on the auditory capacities of proboscideans sounds or low-frequency sounds. Most of these considerations are qualitative and therefore not very precise but they are useful to provide an overall picture of the auditory capacities of fossil mammals.

Coiling of the cochlea

It has been demonstrated that the shape of the cochlea influences greatly the auditory capacities of mammals. Indeed, the cochlear spiral graded curvature enhances sensitivity to low frequencies [START_REF] Manoussaki | Cochlea's graded curvature effect on low frequency waves[END_REF][START_REF] Lebrun | Evolution and development of the strepsirrhine primate skull[END_REF]. The radii ratio (ratio between the radius of the basal turn and the radius of the apical turn of the cochlea) therefore correlates with the low-frequency limit of the animal.

Using the equations given in [START_REF] Manoussaki | The influence of cochlear shape on lowfrequency hearing[END_REF], it is possible to infer the lowfrequency limit of extinct proboscideans.

Measurements of the radius of the apical turn and the radius of the basal turn are necessary to calculate the radii ratio ρ.

These measurements are part of the protocol of [START_REF] Manoussaki | The influence of cochlear shape on lowfrequency hearing[END_REF]. The low-frequency limit of hearing f is then calculated with this equation: However, it should be noted that these calculations are just estimates. First, this method is normally applied on the basilar membrane. This membranous structure is obviously not preserved in fossils; however, the method has already been applied on the bony cochlea of fossils [START_REF] Orliac | The inner ear of Diacodexis, the oldest artiodactyl mammal[END_REF][START_REF] Macrini | Comparative study of notoungulate (Placentalia, Mammalia) bony labyrinths and new phylogenetically informative inner ear characters[END_REF]). On the other hand, the correlations used in [START_REF] Manoussaki | The influence of cochlear shape on lowfrequency hearing[END_REF] are based only on 13 specimens, which is quite small. Estimates calculated with this method therefore must be taken with caution.

Finally, the protocol given in [START_REF] Manoussaki | The influence of cochlear shape on lowfrequency hearing[END_REF] is not very detailed, to the point that we failed to apply the protocol to our data sample. The method is indeed difficult to reproduce and is therefore not used by several authors anymore (pers. comm. Maeva [START_REF] Orliac | The inner ear of Protungulatum (Pan-Euungulata, Mammalia)[END_REF]. Hence, we finally chose not to infer frequency ranges of fossil proboscideans with this method.

Cochlear length and number of turns

The length of the cochlea and its number of turns influence the hearing capacities of mammals. In [START_REF] West | The relationship of the spiral turns of the cochlea and the length of the basilar membrane to the range of audible frequencies in ground dwelling mammals[END_REF], the author succeeds in correlating these two parameters with the low-and highfrequency limits of hearing. Using the product of the absolute bony cochlear 408 VII -Preliminary considerations on the auditory capacities of proboscideans length and the number of turns is a proxy to estimate approximately the hearing capacities of fossil taxa. Indeed, the higher this product, the higher the sensibility of the animal to low frequencies [START_REF] Ekdale | Form and function of the mammalian inner ear[END_REF][START_REF] Manoussaki | The influence of cochlear shape on lowfrequency hearing[END_REF]. The (1985).

On other hand, estimations of the low-frequency limits at 60 dB SPL have then been calculated using the equation given in [START_REF] West | The relationship of the spiral turns of the cochlea and the length of the basilar membrane to the range of audible frequencies in ground dwelling mammals[END_REF]:

1.76 -1.66 * log(𝑏𝑏𝑎𝑎𝑉𝑉𝑏𝑏𝑏𝑏𝑎𝑎𝑏𝑏 𝑚𝑚𝑚𝑚𝑚𝑚𝑏𝑏𝑏𝑏𝑎𝑎𝑚𝑚𝑚𝑚 𝑏𝑏𝑚𝑚𝑚𝑚𝑙𝑙𝑡𝑡ℎ * 𝑚𝑚𝑛𝑛𝑚𝑚𝑏𝑏𝑚𝑚𝑏𝑏 𝑜𝑜𝑓𝑓 𝑡𝑡𝑛𝑛𝑏𝑏𝑚𝑚𝑉𝑉)

However, the method requires measuring the basilar membrane which is not preserved in fossils. The lowfrequency limits were therefore calculated using the length of the cochlear canal which is an approximation of the basilar membrane length. Hence, the limits found with this method can be slightly overestimated.

Basilar membrane and secondary bony lamina

Another feature that can inform us about the hearing capacities of mammals is the basilar membrane. The thickness and stiffness of the basilar membrane correlates with the frequency range of animals [START_REF] Wever | The cochlea of the dolphin, Tursiops truncatus: hair cells and ganglion cells[END_REF][START_REF] Pye | The structure of the cochlea in some mammals[END_REF][START_REF] Ekdale | Form and function of the mammalian inner ear[END_REF]. Mammals with a thick and stiff basilar membrane generally display better sensibilities to high frequency sounds [START_REF] Békésy | Travelling waves as frequency analysers in the cochlea[END_REF]. However, the basilar membrane is not preserved in fossils. To estimate its degree of stiffness and thickness, we must find a proxy capable of estimating the width of the membrane. Generally, authors use the laminar gap, which is the distance between the primary and secondary bony laminae [START_REF] Geisler | The petrosal and inner ear of Herpetocetus sp. (Mammalia: Cetacea) and their implications for the phylogeny and hearing of archaic mysticetes[END_REF]. However, given the fragile nature of the laminae, the estimation of the basilar membrane width using the laminar gap is very imprecise [START_REF] Ketten | Cetacean ears[END_REF]. Therefore, we did not use the laminar gap in our study. Instead, we only noted the absence (or presence) of the secondary bony lamina on the cochlea of our specimens. The absence of a 409 VII -Preliminary considerations on the auditory capacities of proboscideans secondary bony lamina implies a larger and softer basilar membrane, thus a preferential sensibility to low frequencies.

Perilymphatic foramen

The perilymphatic foramen is found only in the earlier stages of development in metatherian and eutherian mammals [START_REF] Fischer | Un trait unique de l'oreille des éléphants et des siréniens (Mammalia) : un paradoxe phylogénétique[END_REF]. Its separation into the fenestra cochleae (opening at the level of the the scala tympani) and the aquaeductus cochleae (which conducts the perilymphatic duct) occurs during the morphogenesis of the ear [START_REF] Kuhn | Die Entwicklung und Morphologie des Schädels von Tachyglossus aculeatus[END_REF][START_REF] Zeller | The morphogenesis of the fenestra rotunda in mammals[END_REF]. However, a few eutherian mammals exhibit an undivided perilymphatic foramen in adults: several extant and fossil sirenians, extant (and some extinct) proboscideans, the embrithopod Arsinoitherium and some cetaceans [START_REF] Fischer | Un trait unique de l'oreille des éléphants et des siréniens (Mammalia) : un paradoxe phylogénétique[END_REF][START_REF] Court | Periotic anatomy of Arsinoitherium (Mammalia, Embrithopoda) and its phylogenetic implications[END_REF][START_REF] Court | Anatomy of the periotic bone in the Eocene Proboscidean Numidotherium koholense : An example of parallel evolution in the inner ear of tethytheres[END_REF][START_REF] Court | The periotic of Moeritherium (Mammalia, Proboscidea) : homology or homoplasy in the ear region of Tethytheria McKenna[END_REF][START_REF] Geisler | The petrosal and inner ear of Herpetocetus sp. (Mammalia: Cetacea) and their implications for the phylogeny and hearing of archaic mysticetes[END_REF][START_REF] Ekdale | Morphology and variation within the bony labyrinth of zhelestids (Mammalia, Eutheria) and other therian mammals[END_REF]. Even though the persistence of a unique perilymphatic foramen is found in early non-therian mammals as well [START_REF] Zeller | The morphogenesis of the fenestra rotunda in mammals[END_REF][START_REF] Zeller | Die Enwicklung und Morphologie des Schädels von Ornithorhynchus anatinus (Mammalia: Prototheria: Monotremata)[END_REF][START_REF] Wible | Petrosals of Late Cretaceous marsupials from North America, and a cladistic analysis of the petrosal in therian mammals[END_REF], its occurrence in some eutherian lineages is considered a derived trait [START_REF] Fischer | Un trait unique de l'oreille des éléphants et des siréniens (Mammalia) : un paradoxe phylogénétique[END_REF]. Previous studies suggest that the persistence of the perilymphatic foramen is to be linked with an adaptation to low-frequency hearing.

Early non-therian mammals exhibiting an undivided perilymphatic foramen are considered low-frequency hearing animals [START_REF] Luo | CT scanning and computerized reconstructions of the inner ear of multituberculate mammals[END_REF]. [START_REF] Court | The periotic of Moeritherium (Mammalia, Proboscidea) : homology or homoplasy in the ear region of Tethytheria McKenna[END_REF] suggests that the persistence of the perilymphatic foramen in extant elephants permits to reduce stiffness within the auditory system which enhances the Estimates of the low-frequency limits using the equations of [START_REF] West | The relationship of the spiral turns of the cochlea and the length of the basilar membrane to the range of audible frequencies in ground dwelling mammals[END_REF] are proportional to the values discussed above and given in Given the approximated values and the high level of intraspecific variability observed here, the differences among this functional will not be thoroughly discussed. However, a few singularities can be pointed out. On the other hand, we observed that proboscideans that display the highest estimated low-frequency limits in our sample exhibit a cochlea which apical turn axis of rotation is not offset with respect to that of the basal turn (character 32 in the phylogenetic analysis). Indeed, Eritherium, Numidotherium,

Stegomastodon, Stegodon and

Platybelodon all exhibit this character and appear to be the proboscideans that display the highest low-frequency limits.

Hence, this morphological feature could potentially be an adaptation to lowfrequency hearing.

Secondary bony lamina

The secondary bony lamina (or This suggests that early proboscideans Eritherium and Phosphatherium were very likely not adapted to hear low frequencies.

lamina
The presence of the lamina in the specimen of Numidotherium described by [START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF] is congruent with the assumed high-frequency capacities of this mammal. The absence of the lamina in the UOK5 specimen could hint to lower frequencies abilities but this is not congruent with the results found with the other methods that all point out that Numidotherium is rather adapted to highfrequency hearing. The loss of the secondary bony lamina appears at the latest in the clade that includes the deinotheriids and the elephantimorphs, which suggests that these taxa display adaptations to low-frequency hearing.

Perilymphatic foramen

As previously discussed (section 'Material and Methods' of this chapter), the presence of a perilymphatic foramen in proboscideans is very likely linked to the ability of hearing low frequencies [START_REF] Court | The periotic of Moeritherium (Mammalia, Proboscidea) : homology or homoplasy in the ear region of Tethytheria McKenna[END_REF]. This feature is generalized in most Procavia (Benoit et al., 2013b) 1.84 Procavia (Ekdale, 2013) 2.10 Prorastomus 1.54 Rhynchocyon (Benoit, 2013) 1.70 Seggeurius [START_REF] Benoit | New material of Seggeurius amourensis (Paenungulata, Hyracoidea), including a partial skull with intact basicranium[END_REF] 1.79 Tenrec (Benoit et al., 2.000 Chambius (Benoit et al., 2013c) 2.000 Chrysochloris [START_REF] Benoit | Comparative anatomy and three-dimensional geometric-morphometric study of the bony labyrinth of Bibymalagasia (Mammalia, Afrotheria)[END_REF] 3.332 Deinotherium (Claudius, 1865) 2.250 Dendrohyrax (Benoit, 2013) 3.669 Dugong (Benoit et al., 2013a) 1.428 Elephantimorpha [START_REF] Ekdale | Morphological variation in the ear region of Pleistocene Elephantimorpha (Mammalia, Proboscidea) from Central Texas[END_REF] 2.125 Elephantulus (Benoit et al., 2013c) 1 (Benoit, 2013) 1.643 Hemicentetes [START_REF] Benoit | Comparative anatomy and three-dimensional geometric-morphometric study of the bony labyrinth of Bibymalagasia (Mammalia, Afrotheria)[END_REF] 1.500

Conclusion

Heterohyrax (Benoit, 2013) 3.681 Hyopsodus [START_REF] Ravel | The inner ear morphology of the 'condylarthran' Hyopsodus lepidus[END_REF] 2.250 Kulbeckia (Ekdale, 2013) 1.280 Microgale [START_REF] Benoit | Comparative anatomy and three-dimensional geometric-morphometric study of the bony labyrinth of Bibymalagasia (Mammalia, Afrotheria)[END_REF] 1.889 Moeritherium [START_REF] Benoit | Evolution des caractères crâniens et endocrâniens chez les Afrotheria (Mammalia) et phylogénie du groupe[END_REF] 2.250

Numidotherium [START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF] 1.500 Numidotherium unlabelled (Benoit et al., 2013b) 1.620

Numidotherium UOK5

1.500 Ocepeia PM45

2.125 Orycteropus [START_REF] Benoit | Comparative anatomy and three-dimensional geometric-morphometric study of the bony labyrinth of Bibymalagasia (Mammalia, Afrotheria)[END_REF] 1.843 Petrodromus (Benoit, 2013) 2.264 Platybelodon 26564 (824+) 2.000 Plesiortycteropus [START_REF] Benoit | Comparative anatomy and three-dimensional geometric-morphometric study of the bony labyrinth of Bibymalagasia (Mammalia, Afrotheria)[END_REF] 1.829

Potamogale [START_REF] Benoit | Comparative anatomy and three-dimensional geometric-morphometric study of the bony labyrinth of Bibymalagasia (Mammalia, Afrotheria)[END_REF] 2.093 Procavia (Benoit et al., 2013b) 3 The ear region of the Proboscidea (Afrotheria, Mammalia): anatomy, function, evolution

Abstract

Elephants are among the few mammals able to hear infra-sounds, and they display a unique locomotor behavior. It corresponds to specializations of their sensory organs contained in the inner ear: the cochlea (audition) and the vestibular system (spatial orientation). While only three species are living today, they were a much more diverse group found in five continents and with a 60 Ma-long history. We provide here the first comprehensive morphological and functional study of the ear region (petrosal, bony and membranous labyrinths) of extant elephants using 3D CT scan techniques. Additionally, we describe and compare the petrosals of fourteen extinct proboscidean genera in order to shed light on the evolution of this anatomical complex in the Proboscidea. The results show that some features of the petrosal and bony labyrinth of extant elephants -such as the number of turns of the cochlea -display a noticeable level of intra-specific variability. Our analysis includes the earliest-known proboscideans and suggests that the petrosal and bony labyrinth morphology evolved gradually during the first half of the proboscidean evolutionary history, but also that the modern morphotype exhibited in elephants was probably already acquired in deinotheriids and generalized in elephantimorphs. Functional inferences on the locomotor behavior and the audition of extinct proboscideans confirm these observations. This work hence provides new insights on the evolution of a major anatomical region hitherto poorly known in an emblematic group of mammals.

  close relatives. The elephants are the largest extant terrestrial mammals and some recent studies on the size and body mass of extinct proboscideans consider that the largest terrestrial mammal in history was also a proboscidean (Palaeoloxodon namadicus, considered to have a shoulder height of 5 m and to weigh 22 t; Larramendi, in press.). There are only three extant representatives of the Proboscidea: the African bush elephant Loxodonta africana, Blumenbach, 1797, the African forest elephant Loxodonta cyclotis, Matschie, 1900, and the Asian elephant Elephas maximus, Linnaeus, 1758. However, they were much more diverse in the past. Their fossil record starts from the middle Paleocene and includes more than 180 known fossil species (Gheerbrant & Tassy, 2009), forming one of the most complete fossil sequences of a modern mammal order. During their 60 million-year-old long history, the proboscideans developed various adaptive morphotypes, from the likely semi-aquatic and tapir-like Moeritherium to the "shovel tusker" Platybelodon. To the present knowledge, the origin of the Proboscidea is deeply rooted in Africa. The first radiation of the proboscideans leads to the appearance of the Paleocene and early Eocene lophodont taxa

  (Mothé et al. 2016b). On the other hand, the Elephantida includes the paraphyletic group of gomphothers from which originate the Stegodontidae Osborn, 1918 and the family that contains the extant elephants (Elephantidae Gray, 1821). The gomphothers are generally classified in three families: the Choerolophodontidae that includes

Figure 1 :

 1 Figure 1 : A hypothesized tree of the Afrotheria, based on Seiffert (2007), except for the debated position of Tubulidentata, left at the base of the Afrotheria here.

  . The position of the Hyracoidea within the Paenungulata is also debated but it is commonly found as the sister-group of Tethytheria McKenna, In mammals, the ear region is mostly comprised of the petrosal which is a complex bone that exhibits many anatomical features. It is located on the ventral part of the skull, generally in contact with the occipital, squamosal and tympanic bones. The anatomy of this bone is commonly studied and compared within the Mammalia. It provides numerous characters that can be tested in phylogenetic analyses. The internal structures of the petrosal are especially crucial to infer functional capacities of extinct taxa. Indeed, the petrosal houses the bony labyrinth which contains the membranous labyrinth in life. This organ has two very important sensory functions: the audition and the detection of motion and spatial orientation. The perception of sound is made by the cochlear part of the labyrinth, whereas the vestibular part of the labyrinth allows the perception of motion and spatial orientation

Figure 2 :

 2 Figure 2 : Illustrations of the ear region of the Proboscidea in the early publications. (A) Anatomical chart of the ear region of an extant elephant given in Blair (1717-1719, Royal Society Publishing), (B) Illustration of the bony labyrinth of an African elephant given in Hyrtl (1845, Bavarian State Library), (C) Illustration of the bony labyrinth of the extinct proboscidean Deinotherium giganteum given in Claudius (1865).

  with one of the only clear anatomical illustrations of a proboscidean petrosal. The recent development of CT scan acquisition methods and their applications to paleontology pave the way to further investigations of the bony labyrinth of extinct taxa. The first attempt to use CT scanning method for the study of the petrosal of an extinct proboscidean dates Introduction is very recent (Elephas tiliensis in Provatidis, 2011). However, the anatomy of the petrosal and the bony labyrinth was not thoroughly studied in this paper. On the other hand, the isolated petrosal of

  to account for the morphological diversity and evolution of the ear region within the Proboscidea, by taking advantage of the recently developed CT scanning methods applied in the field of paleontology. The study of the ear region of the two earliest known elephant relatives Eritherium and Phosphatherium (Schmitt & Gheerbrant, 2016) provides new data on the ancestral morphotype of this region for the Proboscidea and even for the Afrotheria. This published work is part of the PhD thesis and corresponds to the first chapter. The poorly known anatomy of the ear region of extant proboscideans is studied in Chapter II. The petrosals of several specimens belonging to the three extant species of elephants are Introduction investigated with CT scanning methods. A richly illustrated comprehensive study of the region provides a reappraisal of the petrosal and bony labyrinth anatomy, as well as the first 3D reconstructed membranous labyrinth of an extant elephant. Study of several specimens helps to characterize the intraspecific variations of the bony labyrinth and the petrosal, which remains poorly known in mammals. The elucidation of these variations allows refining the comparison between fossil taxa and more importantly the definition of phylogenetic characters. The anatomy of the ear region of most extinct proboscideans remains unexplored; it is described in several extinct proboscideans in Chapter III.

Finally

  Loxodonta cyclotis), as well as from the Asian elephant (Elephas maximus). The mammoth species Mammuthus primigenius and Mammuthus columbi were investigated as well as a specimen of Palaeoloxodon antiquus. Concerning the outgroups, the hyracoid Procavia and the elephant-shrew Elephantulus were scanned. These specimens have been prepared in order to preserve and study their membranous labyrinth in place within the bony labyrinth (more details in chapter VI). Two isolated petrosals of rhinocerotids previously thought to belong toProdeinotherium were also investigated.The earliest afrotherian Ocepeia was segmented as well for comparisons.

Introduction

Figure 4 :

 4 Figure 4 : Landmark sets visualized on the bony labyrinth of Loxodonta MNHN.ZM.AC.1861-53 in frontal, ventral, profile and dorsal view respectively (A). Detailed view of the landmark set of the anterior (B), posterior (C) and lateral (D) canals and of the cochlea (E). In black, external landmarks of the semicircular canals (3 sets in total); in orange, internal landmarks of the slender part of the semicircular canals (3 sets in total); in yellow, internal sets of the ampullae of the semicircular canals (3 sets in total); in red, internal set of the connection between the lateral canal and lateral utricle (1 set); in grey-brown, external set of the cochlea (1 set); in dark blue, external set of the crus commune (1 set); in sky blue, internal set of the crus commune (1 set).

  4D, red set). When the lateral and posterior canals are not fused, this set simply consists of a single type-I landmark placed at the junction of the lateral canal and the vestibule. When the lateral and posterior canals are fused, several landmarks are placed manually on the central streamline of the fused lateral canal and the last landmark is a type-I landmark placed at the junction of the lateral canal and the vestibule. An internal set of landmarks is placed on the central streamline of the ampulla of each canal (Fig. 4B-D, yellow sets). The first landmark (type I) is placed at the level of the crista ampullaris on the central streamline. Semi-landmarks are then placed along the streamline until reaching the intersection with the semicircular canal. Three of these sets are placed on the inner ear (one on each semicircular canal). An external landmarks set is placed along the crus commune (Fig. 4A, dark blue set). The first landmark is a type-I landmark and it is located at the reunion of the anterior and posterior canals streamline. Semi-landmarks are then placed along the crus commune, parallel to its long axis. The last placed landmark is also a type-I landmark and is placed at the basis of the crus. An internal set is placed on the crus commune as well (Fig. 4A, sky blue set). The first landmark is a type-I landmark and is placed at the intersection of the anterior Introduction and posterior canals streamline. Semilandmarks are then placed on the central streamline. The last landmark (type I) is placed at the basis of the crus commune. An external set of landmarks is placed on the cochlea (Fig. 4E, grey-brown set). The first landmark is a type-I landmark and it is located at the top of the fenestra vestibuli. Semi-landmarks are then placed along the external portion of the cochlea (which follows the basilar membrane). The last landmark is placed at the tip of the helecotrema and is a type-I landmark.

Figure 5 :

 5 Figure 5 : 3D view of the bony labyrinth of Loxodonta MNHN.ZM.AC.1861-53 showing the different volumes obtained after the separation protocol. Yellow: cochlea, purple: vestibule, green: anterior semicircular canal, dark blue: posterior semicircular canal, sky blue: lateral semicircular canal, greyblue: crus commune.

  the measurement starts at the first internal landmark of the ampulla (type-I landmark that represents the crista ampullaris) and ends at the level of the intersection of the two canals (first Introduction internal landmark of the crus commune).

  the vertical canals, it considers the torus that consists of the slender part, the crus commune and the part that connects the two structures. It then measures the average between the equivalent radius of the torus perimeter and the radius of the torus area. For the lateral canal, it considers only the slender part of the canal and the straight line that connects both extremities and then measures the average between the radius of the torus perimeter and the radius of the torus area.

  and Phiomia, is the most completely known documentation of the emergence and initial radiation of an extant order of mammals at a remarkably and rarely preserved primitive stage, of one of the most specialized and popular mammals -the elephants. In this work we describe and compare the middle and inner ear morphology of the petrosal of the earliest known proboscideans Phosphatherium and Eritherium, which were both found in the Ouled Abdoun Basin in Morocco, respectively in Selandian (60 Ma; Kocsis et al. 2014; Yans et al. 2014) and early Ypresian phosphate levels (55.5 Ma; Gheerbrant et al. 2003, 2005). The petrosal is a key anatomical region of the skull for the phylogenetic analysis of placental mammals, which is especially significant at high systematic ranks. It is useful for analysis of intra-and interordinal relationships of proboscideans, especially among the Afrotheria, which are at the heart of active researches in several disciplines such as palaeontology and molecular systematics and phylogeny. The labyrinth anatomy remains poorly understood in placentals, and especially in Proboscidea. The middle ear anatomy of Phosphatherium has been partly described (Gheerbrant et al. 2005), but the petrosal of Eritherium and the I -The ear region of earliest known elephant relatives inner ear of Phosphatherium were entirely unknown before this work. Our study of the ear region of these two stem proboscideans was made with the help of CT scan method of examination. We compare the petrosal morphology of Eritherium and Phosphatherium with that of other proboscideans and to other afrotherians, and discuss their significance for augmenting knowledge about the evolution of the morphology of the middle and inner ear among proboscideans and especially for the characterization of the ancestral morphotype of the order.

  illustrated. It is associated with other broken elements of the skull of the same individual, including maxillae, parietals and basicranium, all belonging to specimen PM88. It is a left petrosal covered by a thin pellicle of phosphatic matrix (Fig. I.1). The maxillae associated with the petrosal of specimen PM88 are confidently identified as Eritherium azzouzorum (see Gheerbrant et al. 2012, plate 2), and the size and aspect of the bone of the isolated petrosal indicate that they belong to the same individual. This petrosal is partly damaged by two fissures that run across its surface (one on the tympanic surface and one on the cerebellar surface).

  was based on the nearly complete skull specimens OCP DEK/GE 305 and MNHN.F.PM17. Here we investigate the detailed anatomy of the petrosal, including the inner ear, preserved in MNHN.F.PM17, with the help of CT scanning technology. The scanned specimen MNHN.F.PM17 is an incomplete

Figure I. 1 :

 1 Figure I.1 : Photograph of the isolated petrosal of Eritherium azzouzorum PM88 (scale = 1 cm). (A) Ventrolateral view showing the tympanic surface of the petrosal: pr promontorium, t.t. tegmen tympani. (B) Dorsomedial view showing the cerebellar surface of the petrosal: f.s. location of the fossa subarcuata, p.c. pars cochlearis.

  Eritherium (PM88) and Phosphatherium (MNHN.F.PM17) were scanned at the AST-RX platform of the MNHN (Paris) using a v¦tome¦x L240 from GE Inspection Technologies CT scanner with a voxel size of 10.1 μm for PM88 (voltage: 150 kV, intensity: 270 μA) and 38.6 μm for MNHN.F.PM17 (voltage: 150 kV, intensity: 250 μA). The slices were treated with ImageJ to adjust the contrast and reduce the size of the data. 3D digital reconstructions of the petrosal and inner ear of both specimens were then done at the 3D imagery platform of the MNHN using MIMICS innovation suite software (Materialise ® , release 16).

  cerebellar surface (dorsomedial view, Fig. I.2A) of the petrosal is smooth and carries two large openings: the internal acoustic meatus (meatus acusticus internus) and the subarcuate fossa (fossa subarcuata). These two openings are separated by a large and well-defined ridge called the eminantia arcuata. The subarcuate fossa is very deep and round, and does not carry a petromastoid canal. The internal acoustic meatus is oval and not well-defined. It is separated into two foramina of similar size (the foramen acusticum inferius, which contained the cranial nerve VIII and the foramen acusticum superius, which was I -The ear region of earliest known elephant relatives the exit point of the cranial nerve VII) by a rather narrow and well-defined crista transversa. Whereas the foramen acusticum inferius is round, the foramen acusticum superius is oval, with the major axis of the ellipse oriented anteroposteriorly. The surface around the internal acoustic meatus is relatively smooth. The prefacial commissure, located on the lateral part of the meatus, is large. The foramen singulare is visible and situated in the posterior part of the foramen acusticum inferius. It contained a portion of the cranial nerve VIII (nervus ampullaris posterior canal, Macrini et al. 2010) linked to the posterior ampulla of the vestibule. The tractus spiralis foraminosus is visible and consists of a perforated and spiralled surface related to the vestibulo-cochlear nerve (cranial nerve VIII) (O'Leary, 2010). A groove is visible on the anterior aspect of the pars cochlearis, oriented medially to the internal acoustic meatus. It extends from the anterior extremity of the petrosal to the posterior extremity of the internal acoustic meatus and preserves the track of the inferior petrosal sinus (Ladevèze et al. 2010),

Figure I. 2 :

 2 Figure I.2 : 3D reconstructions and annotated drawings of the left petrosal PM88 of Eritherium (scale = 1 cm) in cerebellar (A), tympanic (B), dorsolateral (C) and ventromedial (D) views: a.p.t.t. anterior part of the tegmen tympani, a.v. bony duct for the aquaeductus vestibuli, c.i. crista interfenestralis, c.t. crista transversa, e.w. epitympanic wing, f.a.i. foramen acusticum inferius, f.a.s. foramen acusticum superius, f.c. fenestra cochleae, f.s. fossa subarcuata, f.t.t. fossa for the tensor tympani, f.v. fenestra vestibuli, j.f. (a.c.) jugular fossa holding the aquaeductus cochleae, g.i.p.s. groove for the inferior petrosal sinus, m.a.i. meatus acusticum internalis, p.c. prefacial commissure, p.f.f. primary facial foramen, p.m. pars mastoidea, p.s. prootic sinus, pr promontorium, r.s.s.a. ramus superior for the stapedial artery, s.f. sulcus facialis, s.s.s. sinus for the sigmoid sinus, t.t. tegmen tympani.

  . I.2C), the tegmen tympani is clearly visible. It is voluminous, bulging, triangular with rounded corners and carries a rather large anterior process. A laterally oriented large canal, which contained the ramus superior for the stapedial artery, is present in the anterior process of the tegmen tympani. Both sinuses described in the cerebellar surface (including the probable sinus for the sigmoid sinus) are also visible in this view. In ventro-medial view (Fig. I.2D), the petrosal has a rather triangular shape (including the missing medial part of the pars canalicularis). The medial surface of the pars cochlearis is bulging, therefore the internal acoustic meatus is not visible in this view. However, the inferior petrosal sinus is clearly visible and extends from the anterior aspect of the pars cochlearis to the fissure. The cochlear canaliculus, which has been damaged by the fissure, cannot be described in this view.

  endocast of the bony labyrinth of Eritherium is reconstructed in Fig. I.3. The cochlea of Eritherium is partially broken and the number of turns is approximately 2 (720°). The total spiral length of the cochlea is 14.13 mm. In dorsal view, the first turn (basal turn) appears to be larger and overlaps the second turn (apical turn). In lateral view, the cochlea is flattened with an aspect ratio of 0.35. This morphology seems to be natural because no major distortion of the petrosal is visible. The cochlear canaliculus could not be reconstructed because it was located in the long fissure running through the petrosal, but it was probably present. The fenestra cochleae and the cochlear canaliculus are therefore most likely separated from each other and not merged in a common perilymphatic foramen. The fenestra cochleae is subrectangular, with rounded corners.

Figure I. 3 :

 3 Figure I.3 : 3D reconstructions of the Eritherium bony labyrinth (scale = 5 mm) in ventral (A), posterior (B), dorsal (C), lateral (D) and medial (E) views: a.amp. anterior ampulla, a.s.c. anterior semicircular canal, a.v. aquaeductus cochleae, c.c. crus commune, co. cochlea, f.c. fenestra cochleae, f.v. fenestra vestibuli, l.amp. lateral ampulla, l.s. lamina secundaria, l.s.c. lateral semicircular canal, n.a.a. nervus ampullaris anterior, n.a.p. nervus ampullaris posterior, p.amp. posterior ampulla, p.s.c. posterior semicircular canal, sa. saccule.

  . I.4A), the subarcuate fossa and internal acoustic meatus are separated by a shallow eminantia arcuata. The internal acoustic meatus is rather large, ellipsoid and elongated antero-posteriorly. The subarcuate fossa -which was not visible without the CT scan because of the encrusting phosphate matrix -is larger than the internal acoustic meatus and of moderate depth, its outline forming an antero-posteriorly stretched-out ellipse. The subarcuate fossa of the other specimen of Phosphatherium (OCP DEK/GE 305) is described as deep in Gheerbrant et al. (2005) but it is in fact moderately deep in comparison with the I -The ear region of earliest known elephant relatives fossa in Eritherium. However, the depth of this fossa shows some intra-specific variability in Phosphatherium escuilliei because it is clearly deeper on OCP DEK/GE305 than on PM17. Compared with Eritherium, the subarcuate fossa of Phosphatherium is also longer in an antero-posterior position. The foramen acusticum superius is ellipsoid; its long axis is aligned with the long axis of the petrosal. Despite the area being broken, we estimate that the foramen acusticum inferius was round. These two foramina are delimited by a partially damaged, narrow and sharp crista transversa. The surface around the meatus is smooth and the foramen singulare pierces the foramen acusticum inferius in its posterior part, as in Eritherium. The tractus spiralis foraminosus is not visible because of the poor preservation of the foramen . I.4B), the promontorium is bulging, hemi-ellipsoid and located on the medial part of the petrosal. It is damaged, which allows the observation of some internal characters of the cochleae. No sulcus is observable on the promontorium, which could be explained by the absence of these structures or the poor state of preservation of the promontorium. Lateral to the promontorium, the fenestra vestibuli opens ventro-laterally. It appears to be slightly oval but it is considered to be round with a stapedial ratio of 1.62 (stapedial ratio < 1.7; Benoit et al. 2013b). The fenestra cochleae is located posterior to the promontorium, and is oriented towards the posterior surface of the petrosal. It is sub-rectangular with rounded corners and is almost twice as large as the fenestra vestibuli, in contrast to Eritherium, which shows a f. vestibuli slightly larger than the f. cochleae. The fenestrae are separated by quite a large and flat crista interfenestralis. The secondary facial foramen, which corresponds to the exit of the facial nerve, is also visible. The facial sulcus that conveyed the facial nerve from the secondary facial foramen is C-shaped. The fossa for the stapedial muscle is present posterolateral to the fenestra vestibuli and is followed by the facial sulcus.

Figure I. 4 :

 4 Figure I.4 : 3D reconstructions and annotated drawings of the right petrosal MNHN.F PM17 of Phosphatherium (scale = 5 mm) in cerebellar (A), tympanic (B), medial (C) and anterior (D) views: a.c. aquaeductus cochlea, a.v. bony duct for the aquaeductus vestibuli, c.i. crista interfenestralis, c.t.crista transversa, e.a. eminantia arcuata, f.a.i. foramen acusticum inferius, f.a.s. foramen acusticum superius, f.c. fenestra cochleae, f.s. fossa subarcuata, f.v. fenestra vestibuli, g.i.p.s. groove for the inferior petrosal sinus, h.F. hiatus Fallopii, m.a.i. meatus acusticum internalis, p.c. prefacial commissure, pr. promontorium, s.f. sulcus facialis, s.f.f. secondary facial foramen, s.s.s. sinus for the sigmoid sinus.

Figure I. 5 :

 5 Figure I.5 : 3D reconstructions of the Phosphatherium bony labyrinth (scale = 5 mm) in ventral (A), posterior (B), dorsal (C), lateral (D) and medial (E) views: a.amp. anterior ampulla, a.s.c. anterior semicircular canal, a.c. aquaeductus cochleae, a.v. aquaeductus vestibuli, c.c. crus commune, c.c.s. crus commune secundaria, co. cochlea, f.c. fenestra cochleae, f.v. fenestra vestibuli, l.amp. lateral ampulla, l.s. lamina secundaria, l.s.c. lateral semicircular canal, p.amp. posterior ampulla, p.s.c. posterior semicircular canal, sa. saccule, ut. utricle.

  18 petrosal characters seen in Eritherium and Phosphatherium. The definition of most of these characters follows Benoit et al. (2013a-c). Seven characters are not modified; eight characters come from the previously cited studies and were modified; two characters come from O'Leary (2010) and Wible et al. (2009) and were modified; one new character was defined and analyzed in this study. Numerous characters in Benoit et al. (2013a-c) are not retained here because they were constant among our sampled taxa.

(

  homoplasy index HI = 0.753) (Appendix 4), probably due to several convergences, as already discussed by Benoit et al. (2013b). The unresolved polytomy obtained in the consensus tree (see Appendix 4) does not allow us to discuss the distribution of the characters observed in Phosphatherium and Eritherium at an intra-ordinal level. The use of other members of Afrotheria or Placentalia as outgroups of Proboscidea in our analysis did not provide resolved topology at either inter-or intra-ordinal levels because of the high level of homoplasy. Consequently, we developed and carried out a cladistic analysis of the petrosal features of Phosphatherium and Eritherium that is restricted to the Proboscidea. Because the petrosal and inner ear morphology remains poorly known among proboscideans, the analysis I -The ear region of earliest known elephant relatives was restricted to the few taxa where petrosal characters have been described: Eritherium and Phosphatherium,

  [START_REF] Ruf | Petrosal anatomy and inner ear structures of the late Jurassic Henkelotherium (Mammalia, Cladotheria, Dryolestoidea): insight into the early evolution of the ear region in cladotherian mammals[END_REF] were used as outgroup taxa, bringing to eight the total number of analyzed taxa. It should be stressed that this is only a preliminary study, aiming at a first look at the distribution of the characters of Phosphatherium and Eritherium and of their significance for understanding the morphological evolution of the petrosal in Proboscidea. These characters should be later included in a larger matrix including other characters and extended to at . I.6). The consistency index (CI) and retention index (RI) are high (CI = 0.905; RI = 0.833): The tree shows a very low level of homoplasy. In this tree, it should be noted that the monophyly of the Proboscidea is not tested because the analysis does not include other taxa of the Paenungulata and Afrotheria. In such a of the Proboscidea in our tree, two synapomorphies are seen (Fig. I.6B), one being non-homoplastic. First, the transpromontorial sulcus is lost [8(0)] in Proboscidea. This is a homoplasy (CI = 0.5) because the character is reversed in Numidotherium, which shows a transpromontorial sulcus on its promontorium according to Benoit et al.

Figure I. 6 :

 6 Figure I.6 : Results of the cladistic analysis of the petrosal features of Eritherium and Phosphatherium within Proboscidea: (A) phylogenetic tree replacing the taxa in temporal context; (B) most parsimonious cladogram obtained with our analysis. Length = 21 steps. Consistency index (CI) = 0.905. Homoplasy index (HI) = 0.095. Retention index (RI) = 0.833. Rescaled consistency index (RC) = 0.754. Numbers of non-homoplastic characters are represented with diamond symbols, and numbers of homoplastic characters are represented with circles. The state number is specified after the character number. Bremer indexes are indicated right to the nodes.

  in our analysis by six nonhomoplastic synapomorphies. The cochlear aqueduct and the fenestra I -The ear region of earliest known elephant relatives cochleae are not separated, forming a unique perilymphatic foramen [2(1)]. This state has an unambiguous location, whereas the other synapomorphies are ambiguous probably because the inner ear characters are unknown in Moeritherium and Gomphotherium. The cross-section of the semi-circular canals is flattened [12(1)], there is no longer a fusion of the posterior and lateral semi-circular canals [13(1)], the aspect of the semi-circular canals is stocky [14(1)], the position of the lateral semi-circular canal is low [15(1distribution of petrosal and inner ear characters among the order Proboscidea. However, the absence in the analysis of other afrotherian and placental taxa prevents discussion of the synapomorphies of the ear region at the base of the clade Proboscidea and the evolution of these characters among Tethytheria, Paenungulata, Afrotheria and Eutheria. To assess the evolution of the characters seen in Eritherium and Phosphatherium at a higher level than Proboscidea, we compared some important features of the ear region among several other placentals and eutherians; this is summarized in Table I.3. Each order is represented by the closest representative to the ancestral morphotype of the group, i.e. its most primitive representative(s) for which petrosal features are known. The plesiomorphic states of characters among Xenarthra were determined based on the study of Billet et al. (2015). States of other taxa were taken from the references mentioned above ( §4.2). This comparison is preliminary and should be tested further and developed in the future with extended cladistic analyses.

  therefore likely a synapomorphy of the clade including Moeritherium, the Deinotheriidae and the Elephantidae.

  Eritherium is clearly more primitive than that of Phosphatherium and is closer to the basal afrotherian paenungulate Ocepeia in several symplesiomorphies such as the morphology of the tegmen tympani region, the extremely deep fossa subarcuata and an ossified canal for the superior ramus of the stapedial artery. early proboscideans. The partial fusion of the lateral and posterior semicircular canal is shared by Eritherium and Ocepeia, but it differs from the of the best among placental orders, and Eritherium and Phosphatherium are two of the earliest known and most primitive representatives of extant placental orders. Therefore, they provide new insights concerning the ancestral morphotype of petrosal anatomy not only of Proboscidea but also I -The ear region of earliest known elephant relatives at a supra-ordinal level among placentals (e.g. paenungulates and afrotherians). Previous studies showed important homoplasy in the ear region of Tethytheria (Benoit et al. 2013b), which is also supported by our analysis including Proboscidea and other eutherians. Here, the restriction of the analysis to Proboscidea provides a topology close to the consensual phylogenetic tree of Proboscidea, but most noticeably with low homoplasy indexes. This shows that the evolutionary modalities of the ear region characters after the ordinal radiation. This is consistent with previous conclusions based on cranial and dental characters of Eritherium.

  bony labyrinth has been rapidly investigated inBenoit et al. (2013b) but a detailed study of these internal structures in extant elephants has yet to be conducted. Studying the evolution of the ear region within the Proboscidea requires a good knowledge of this structure in extant taxa. Hence, we decided to focus this chapter on the anatomy of the petrosal and the bony labyrinth of extant elephants prior to discussing the ear region of fossil proboscideans in Chapter III. We took advantage of the relatively recent development of microtomographic CT data analyses in the field of anatomical investigations. The main objective is to provide the first comprehensive anatomical study of the ear region of extant elephants. The location of the petrosal within the skull and its position with respect to other bones is clarified. A detailed and richly illustrated anatomical description of the petrosal is given. 3D models of the bony labyrinth are segmented in high resolution. Finally, the first microtomographic 3D reconstruction of the membranous vestibular system of an elephant is carried out in this chapter. The comprehensive study of the ear region in extant taxa provides primary and key comparative data for the anatomical descriptions of extinct taxa. The segmentation of the petrosal and bony labyrinth of several specimens of each extant species allows us to discuss intraspecific variations of this anatomical region as well. These considerations are useful because the descriptions of fossil taxa are generally based on one specimen.

Four specimens of

  Elephas maximus have been studied. Among them, three skulls from the collections of the MNHN were CT-scanned. There are no isolated petrosals belonging to extant elephants in the MNHN collections which explains why we scanned these complete skulls. On the other hand, scanning petrosals still connected to the skull allows us to control the taxonomic assignment of the ear bone as it is not unusual for isolated bones to be incorrectly assigned in centuries-old collections. The major difficulty was to find specimens that could fit in the CT-scan. It is not possible to fit very large specimens in the scanning machine available at the MNHN and the greater the specimens the lower the resolution. Therefore, we chose skulls belonging to juveniles and young adults. The first skull MNHN.ZM.AC.1904-273 is a juvenile of which both bony ears were CTscanned. However, the scanning of the left ear was unsuccessful so we could only segment the right ear. The second skull MNHN.ZM.AC.1941-209 is a juvenile (died at 5 years) which comes from Indochine. Only its left ear was scanned. ZM.AC.2008-81) was CT-scanned. There are no additional details about the age and provenance of this specimen in the MNHN collection database. A fourth specimen CEB 150009 was studied. It consists of a newborn elephant that died following a cranial trauma at an early age (less than three months old). This elephant was a resident of the Leipzig zoo. The head was collected less than 48 hours after its death and preserved in Bouin solution. The ear region was then cut off for CT investigations. This allowed us to obtain a 3D model of the membranous structures of the labyrinth contained in the bony inner ear. Since this specimen was cut and the scan was only focused on the labyrinth, it was not possible to segment the petrosal for this specimen. Loxodonta Ten specimens of Loxodonta have been studied. Until recently, the two extant species L. africana, African savannah (or bush) elephant and L. cyclotis, African forest elephant, were considered sub-species of a single African elephant species: Loxodonta africana.

  majority of the studied specimens are labelled Loxodonta africana in the MNHN collection database without further details about the sub-species. Furthermore, skulls belong to the collections of the MNHN. As for the Elephas skulls, we chose to sample small skulls that could fit in the CT-scan. Hence we studied preferably juveniles and young adults. The first skull MNHN.ZM.AC.1950-728 has been attributed to the species Loxodonta cyclotis based on the original labelling which assign this specimen to the invalid species Loxodonta pumilio. This invalid species refers to the African pygmy forest elephant which status has been debated. The species was abandoned after a molecular study highlighted the inclusion of the African pygmy elephants within a monophyletic group of forest elephants sensu lato (Debruyne et al. 2003). No other details were available on this specimen but its provenance (Gabon) is given in Debruyne et al. (2003). The right ear of this specimen was CT-scanned. Another skull from Cameroun and attributed to the invalid species Loxodonta pumilio MNHN.ZM.AC.1956-194 is reattributed to Loxodonta cyclotis. In addition to its right ear, the entire skull of this specimen was scanned. Given the great size of this skull, it needed several acquisitions to scan it completely. A third specimen MNHN.ZM.AC.1957-465, although not labelled Loxodonta pumilio, corresponds in the collection database to "éléphant nain du Gabon" (pygmy elephant from Gabon), that is the species L. cyclotis. Its left ear was CT-scanned. A fourth specimen MNHN.ZM.AC.1961-69 is attributed to L. cyclotis based on geographical provenance details (Gabon) and its right ear was CT-scanned. Additional details inform us that this individual died at 15 days which explains its particularly small size. The fifth specimen MNHN.ZM.AC.1861-53 comes from Sudan and died at 8 years. It is assigned to L. africana based on geographical data. The three other skulls were left unassigned to a Loxodonta species because we could not identify them without doubts. Hence we refer them to as Loxodonta sp. No details are given concerning the sixth specimen MNHN.ZM.AC.1932-523 which right ear was CT-scanned. The left ear of the seventh specimen MNHN.ZM.AC.2008-70, was CT-scanned but the inside of skull was shattered and only a small part of the petrosal was still present. Finally, both ears of MNHN.ZM.AC.2008-71 were CTscanned in order to have at least one full set of ears of the same specimen to compare. Additional details from the MNHN collection database tell us that this specimen was a juvenile. On the other hand, a left isolated petrosal of an African bush elephant (Loxodonta africana) had been CT-scanned several years ago for investigation. The microtomographic slices were used for

  at the IWF in Berlin (2015). It was kept in Bouin solution for several weeks before extracting the petrous bone. Following the protocols described in David et al. (in press), the II -Petrosal and inner ear anatomy of extant elephants petrosal was dehydrated in several baths of alcohol of various concentrations and was then stained in a phosphotungstic acid solution for several weeks before scanning. The scanning was done at

3. 1 .

 1 The auditory region and its location in the skullThe auditory region consists, in elephants (and in mammals in general), of several bones located in the basicranial part of the skull(Fig II.2). In veterinary studies, the squamosal, petrosal and tympanic bones are considered to form a unique bone called the temporal. Hence, it is common to come across different nomenclature terms when talking about the petrosal. In[START_REF] Van Der Merwe | The skull and mandible of the African elephant (Loxodonta africana)[END_REF] for instance, the petrosal of elephants is referred to as the petrous part (pars petrosa) of the temporal bone.Here, I will refer to the tympanic, petrosal and squamosal as distinct bones. The structures of the inner ear are contained in the petrosal. This bone is partially fused (medially and caudally) with the tympanic bone which forms the tympanic bulla and is in contact with the squamosal and the occipital. In addition, there are three small bones (actually the smallest bones in mammals) located in the tympanic cavity that form the auditory ossicles chain: the malleus, the incus and the stapes (which is in contact with the fenestra vestibuli of the petrosal). The study of the auditory region of a complete elephant skull (especially the petrosal) is difficult because most of the structures are located in the endocranial part of the skull and therefore are not visible directly on the skull. In ventral view, the petrosal is only visible at the level of the stylomastoid foramen (that contains the facial nerve, VII) which is delimited by the tympanic and the petrosal in its most internal part, and by the occipital and the squamosal in its most external part. This is confirmed in Van Der Merwe et al. (1995). The petrosal is impossible to observe in this view because it is located under the tympanic. The tympanic is more or less bulbous in ventral view because of the tympanic bulla. The canalis musculotubarius leaves the tympanic antero-medially. This canal is for the Eustachian tube (Van Der Merwe et al. 1995). The tympanic bulla delimits medially the canalis caroticus with the occipital. Posteriorly, the occipital and the tympanic delimit the jugular foramen that opens ventrally and probably housed the hypoglossal nerve (XII). In the lateral part of the skull, the processus retrotympanicus and the processus retro-articularis of the squamosal form the external auditory II -Petrosal and inner ear anatomy of extant elephants meatus which is the entry point of the external auditory canal and opens laterally. The notch located between the two processes is called the incisura tympanica. The external auditory canal is delimited by the squamosal for its most external part and then by the petrosal bone antero-dorsally and the tympanic bone postero-ventrally until it reaches the tympanic cavity of the middle ear. In one specimen (Elephas MNHN.ZM.AC.1941-209), I was able to reconstruct a thin empty tubular structure located inside the external auditory meatus (Fig. II.1).

Figure II. 1 :

 1 Figure II.1 : 3D reconstruction of the petrosal of Elephas specimen MNHN.ZM.AC.1941-209 and its probable cartilaginous gutter. Legends: c.g. cartilaginous gutter?, in incus, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, t.t. tegmen tympani

Figure II. 2 :

 2 Figure II.2 : Position of the petrosal (blue) in the skull of L. cyclotis 1956-194 in lateral (A), caudal (B), ventral (C) and antero-dorsal (D) views. Virtual dissections of the basicranium in ventral view (E) with a focus on the stylomastoid foramen (F) and in antero-dorsal view (H) with a focus on the petrosal (G). Legends: a.v. aquaeductus vestibuli, c.c. canalis caroticus, c.m. canalis musculotubarius, c.p.p. crista partis petrosa, cbl.s. cerebellar surface of the petrosal, cbr.s. cerebral surface of the petrosal, e.a.m. external auditory meatus, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, j.f. jugular foramen, o.c. occipital condyle, occ occipital, pe petrosal, p.r. processus retrotympanicus, s.f. stylomastoid foramen, sq squamosal, t.b. tympanic bulla, t.i. tympanic incisura, ty tympanic.

  following section focuses on the anatomical description of the extant elephants petrosal. Detailed anatomical drawings of one petrosal of Elephas (MNHN.ZM.AC.2008-81) and one petrosal of Loxodonta (MNHN.ZM.AC.1957-465) in ventral and dorsal views are given in Fig. II.3 and II.4 respectively. They allow observing the general morphology of the extant elephants petrosal. On the other hand, less detailed anatomical charts representing the petrosal in tympanic, medial, cerebral and cerebellar views are given for each studied specimen (Fig. II.12-20). These charts are more schematic and allow observing the several variations observed within the sample. In dorsal view, the petrosal displays two surfaces separated by a ridge called the crista partis petrosa: the cerebellar surface that bears the internal acoustic meatus and the subarcuate fossa, and the cerebral surface that displays a deep vascular groove. These surfaces form an obtuse angle of roughly 110°. Contrary to the observation made by Tassy (2013), the crista partis petrosa appears less sharp in extant elephants than in Gomphotherium angustidens.

Figure II. 3 :

 3 Figure II.3 : Petrosal of Elephas MNHN.ZM.AC.2008-81 in ventral (A) and dorsal (B) views (mirrored). Illustrations by Charlène Letenneur (MNHN, CR2P). Legends: a.F. aquaeductus Fallopii, a.v. aquaeductus vestibuli, b.r.a.F. bony roof over the aquaeductus Fallopii, c.i. crista interfenestralis, c.p.p. crista partis petrosa, e.w. epitympanic wing, g.m.m.a. groove for the middle meningeal artery, h.F. hiatus Fallopii, i.a.m. internal auditory meatus, o.p.c. opening of a pneumatic cell, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal, t.t. tegmen tympani, ty tympanohyal.

Figure II. 4 :

 4 Figure II.4 : Petrosal of L. cyclotis MNHN.ZM.AC.1957-465 in ventral (A) and dorsal (B) views. Illustrations by Charlène Letenneur (MNHN, CR2P). Legends: a.F. aquaeductus Fallopii, a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, e.w. epitympanic wing, g.c.p.p. groove under the crista partis petrosa, g.m.m.a. groove for the middle meningeal artery, h.F. hiatus Fallopii, i.a.m. internal auditory meatus, o.p.c. opening of a pneumatic cell, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal, t.t. tegmen tympani.

  bone to bone segmentation allowed us to separate the tympanic from the petrosal in order to visualize only the latter. The lateral part of the petrosal consists of the large and flat tegmen tympani. It is bound laterally to the squamosal and fused antero-medially to the tympanic. The postero-lateral part of the tegmen tympani forms the most inner part of the external auditory canal with the tympanic.

  .2 below). Illustrations of the fenestrae vestibuli are given in Fig. II.5.

Figure II. 5 :

 5 Figure II.5 : Fenestrae vestibuli of Elephas specimens 1904-273 (A), 1941-209 (B) and 2008-81 (C) and Loxodonta specimens 1861-53 (D), 1950-278 (E), 1957-465 (F), 1961-69 (G), 2008-71 left (H), 2008-71 right (I) and CEB130168 (J). The fenestra vestibuli opens over the aquaeductus Fallopii (or Fallopian canal) that contained the facial nerve in

  hypothesis. I was able to reconstruct the pneumatic cells which are clearly contained in the petrosal and do not connect with the pneumatic cells of the tympanic. Hence, I assume that the most posterior part of the process is clearly part of the petrosal (and referred it to as the pars mastoidea) while the anterior part is part of the tympanic. The pneumatic cells contained in the pars mastoidea are represented in Figure II.6. Their number and shape vary significantly between specimens.

Figure II. 6 :

 6 Figure II.6 : Pneumatic cells of the pars mastoidea viewed in transparency, in medial view, in Elephas specimens MNHN.ZM.AC.1904-273 (A), 1941-209 mirrored (B), 2008-81 (C), L. africana specimen MNHN.ZM.AC.1861-53 (D), Loxodonta sp specimens MNHN.ZM.AC.1932-523 (E), 2008-71 left mirrored (I) and 2008-71 right (J) and L. cyclotis specimens MNHN.ZM.AC.1956-194 (F), 1957-765 mirrored (G) and 1961-69 (H). The cells are in red and yellow. Cells with the same color appear to be homologous.

Figure II. 7 :

 7 Figure II.7 : Reconstruction of the course of the facial nerve (violet) in L. africana 1861-53 using bony canals. a.F. aquaeductus Fallopii, a.v. aquaeductus vestibuli, co cochlea, f.v. fenestra vestibuli, g.g. geniculate ganglion, s.c. stylomastoid canal, s.f. stylomastoid foramen, v.c.n. vestibulo-cochleae nerve.

  over the abducens nucleus to form the facial colliculus, and then extends ventrally to exit at the pontomedullary junction ventral to the vestibulocochlear nerve" (Maseko et al. 2013). It was possible to reconstruct the course of the facial nerve in the auditory region (Fig. II.7). The nerve enters the petrosal through the hiatus Fallopii and runs inside the Fallopian canal. It passes close to the fenestra vestibuli and widens where the roof of the Fallopian canal is open. This is probably the location of the geniculate ganglion. The further course of the facial nerve deviates laterally and enters the pars mastoidea of the petrosal via the stylomastoid canal. It then exits the skull through the stylomastoid foramen. Close to the crista interfenestralis on its posteromedial side is the tympanohyal which is part of the pars mastoidea. It has the aspect of a rather sharp ridge that overhangs the canal for the facial nerve. Laterally to the perilymphatic foramen lies a deep fossa that housed the stapedius muscle. This muscle is attached to the stapes and permits its movements. The fossa communicates with the area where the stapes is located in life through a foramen called the stapedial foramen. Ekdale (2011) highlighted a variation of the stapedial foramen in petrosals of elephantimorphs and I observe a variation of this area as well in extant elephants. In some specimens, the tympanohyal and the crista interfenestralis are in contact thus delimiting a true stapedial foramen (Elephas 1904-273, Loxodonta 1956-194 and in both ears of 2008-71, Fig. II.8A). However, the tympanohyal is located somewhat more distant from the crista interfenestralis in other specimens. In Loxodonta specimens 1961-69 and 1950-278 and Elephas specimens 1941-209 and 2008-81, the tympanohyal and the crista interfenestralis are not strictly in contact (but extremely close), thus the stapedial foramen is not fully delimited (Fig. II.8B).

Figure II. 8 :

 8 Figure II.8 : Variations of the stapedial foramen: (A) fully delimited (Elephas 1904-273), (B) partially delimited (Elephas 2008-81) and (C) poorly delimited (L. cyclotis 1957-465).Legends: c.i. crista interfenestralis, f.m. fossa for the stapedius muscle, p.f. perilymphatic foramen, pr promontorium, ty tympanohyal.

  .AC.2008-71, the ossicles are even in connection (Fig. II.11A). The malleus is the most lateral ossicles and its manubrium attaches the tympanic membrane in life. It is articulated with the incus at the level of the articular surface. The short process of the incus is lodged in a shallow depression located on the surface of the petrosal: the fossa incudis (Fig. II.11B). The incus is articulated with the stapes whose footplate occupies the fenestra vestibuli.

Figure II. 11 :

 11 Figure II.11 : Complete ossicular chain of an African elephant (A) and articulation region of the ossicles (B). c.i. crista interfenestralis, f.i. fossa incudis, f.v. fenestra vestibuli, in incus, ma malleus, pr promontorium, st stapes, ty tympanohyal.

Figure II. 12 :

 12 Figure II.12 : 3D models and drawings of the right petrosal of Elephas maximus MNHN.ZM.AC.1904-273 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, e.w. epitympanic wing, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, o.p.c. opening of a pneumatic cell, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal, t.t. tegmen tympani, ty tympanohyal

Figure II. 13 :

 13 Figure II.13 : 3D models and drawings of the left petrosal of Elephas maximus MNHN.ZM.AC.1941-209 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, e.w. epitympanic wing, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, o.p.c. opening of a pneumatic cell, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal, t.t. tegmen tympani, ty tympanohyal

Figure II. 14 :

 14 Figure II.14 : 3D models and drawings of the right petrosal of Elephas maximus MNHN.ZM.AC.2008-81 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, e.w. epitympanic wing, f.v. fenestra vestibuli, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, o.p.c. opening of a pneumatic cell, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal, t.t. tegmen tympani, ty tympanohyal

Figure II. 15 -

 15 Figure II.15 -3D models and drawings of the right petrosal of Loxodonta africana MNHN.ZM.AC.1861-53 in tympanic (A), medial (B), cerebellar (C) and cerebral (D) views. Legends: a.F. aquaeductus Fallopii, a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, e.w. epitympanic wing, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, o.p.c. opening for a pneumatic cell, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal, t.t. tegmen tympani, ty tympanohyal.

Figure II. 16 :

 16 Figure II.16 : 3D models and drawings of the right petrosal of Loxodonta sp. MNHN.ZM.AC.1932-523 in tympanic (A), medial (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, o.p.c. opening of a pneumatic cell, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal, t.t. tegmen tympani, ty tympanohyal.

Figure II. 17 :

 17 Figure II.17 : 3D models and drawings of the right petrosal of Loxodonta cyclotis MNHN.ZM.AC.1956-194 in tympanic (A), medial (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, g.m.m.a. groove for the middle meningeal artery, gr cerebral groove, i.a.m. internal auditory meatus, o.p.c. opening of a pneumatic cell, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, prot protuberance, s.c. stylomastoid canal, t.t. tegmen tympani, ty tympanohyal.

Figure II. 19 :

 19 Figure II.19 : 3D models and drawings of the left petrosal of Loxodonta sp. MNHN.ZM.AC.2008-71 in tympanic (A), medial (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.i. crista interfenestralis, e.w. epitympanic wing, f.v. fenestra vestibuli, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, prot protuberance, s.c. stylomastoid canal, t.t. tegmen tympani, ty tympanohyal

Figure II. 21 :

 21 Figure II.21 : Comparative chart representing the 3D reconstructions of the bony labyrinths of extant elephants in ventral view. Elephas specimens: MNHN.ZM.AC.1904-273 (A), 1941-209 (B), 2008-81 (C) and CEB 150009 (D). Loxodonta specimens: MNHN.ZM.AC.1861-53 (E), 1932-523 (F), 1950-278 (G), 1956-194 (H), 1957-465 (I), 1961-69 (J), 2008-71 left ear (K), 2008-71 right ear (L) and CEB130168 (M). Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, co cochlea, f.v. fenestra vestibuli, he helicotrema, l.a. lateral ampulla, l.c. lateral semicircular canal, mo modiolus, p.c. posterior semicircular canal, p.f. perilymphatic foramen.

Figure II. 22 :

 22 Figure II.22 : Comparative chart representing the 3D reconstructions of the bony labyrinths of extant elephants in the plane of the anterior canal. Elephas specimens: MNHN.ZM.AC.1904-273 (A), 1941-209 (B), 2008-81 (C) and CEB 150009 (D). Loxodonta specimens: MNHN.ZM.AC.1861-53 (E), 1932-523 (F), 1950-278 (G), 1956-194 (H), 1957-465 (I), 1961-69 (J), 2008-71 left ear (K), 2008-71 right ear (L) and CEB130168 (M). Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea, l.c. lateral semicircular canal, p.c. posterior semicircular canal

Figure II. 24 :

 24 Figure II.24 : Comparative chart representing the 3D reconstructions of the bony labyrinths of extant elephants viewed in the plane of the lateral canal. Elephas specimens: MNHN.ZM.AC.1904-273 (A), 1941-209 (B), 2008-81 (C) and CEB 150009 (D). Loxodonta specimens: MNHN.ZM.AC.1861-53 (E), 1932-523 (F), 1950-278 (G), 1956-194 (H), 1957-465 (I), 1961-69 (J), 2008-71 left ear (K), 2008-71 right ear (L) and CEB130168 (M). Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, c.c. crus commune, co cochlea, l.a. lateral ampulla, l.c. lateral semicircular canal, mo modiolus, p.a. posterior ampulla, p.c. posterior semicircular canal, p.f. perilymphatic foramen.

Figure II. 25 :

 25 Figure II.25 : Comparative chart representing the 3D reconstructions of the bony labyrinths of extant elephants in frontal view. Elephas specimens: MNHN.ZM.AC.1904-273 (A), 1941-209 (B), 2008-81 (C) and CEB 150009 (D). Loxodonta specimens: MNHN.ZM.AC.1861-53 (E), 1932-523 (F), 1950-278 (G), 1956-194 (H), 1957-465 (I), 1961-69 (J), 2008-71 left ear (K), 2008-71 right ear (L) and CEB130168 (M). Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea, f.v. fenestra vestibuli, he helicotrema, l.a. lateral ampulla, l.c. lateral semicircular canal, mo modiolus, p.c. posterior semicircular canal, p.f. perilymphatic foramen.

  anterior duct. Its crosssection is circular contrary to the flattened cross-section of the bony ducts. The thickness of the slender part of the anterior duct is rather constant along the duct except at the level of its connection with the crus commune and at the level of its connection with the anterior ampulla where the slender part of the duct progressively thickens. This results in a lesser defined ampulla in Elephas than in Procavia and Elephantulus which do not exhibit such thickening at this location. Hence, the thickening of the canals resulting in poorly defined bony ampullae in the bony labyrinth of extant elephants is a feature also observed in the membranous labyrinth, but to a lesser extent. The slender anterior duct enters almost parallel to the great axis of the anterior ampulla, contrary to Procavia and Elephantulus in which the duct enters the ampulla more ventrally (especially in Procavia). On the other hand, the angle formed by the slender anterior duct and the crus commune at the level of their connection is similar to that of Procavia and Elephantulus. The crus commune length represents only a small part of the total anterior semicircular duct length (one sixth at most). This differs from Procavia and Elephantulus which crus commune represents around one fourth of the total length of the anterior duct. It does not exhibit a particular curving in any of the sampled afrotherians. Its cross-section is thicker (approximately twice) than that of the slender duct. From the apex to the base of the crus, the area of the crosssection increases. In parallel, the crosssection of the crus commune changes from an oval form (close to the apex) to a rounder form (close to the base). The distal part of the crus commune is connected slightly obliquely to the proximal part of the common utricle. This utricular section is the part where the streamlines of all three semicircular ducts meet. It is strikingly thick in elephants compared to Procavia and Elephantulus, and even to mammals in general (pers. comm. Romain David 2016).

Figure II. 26 :

 26 Figure II.26 : Bony (A,D,G), membranous (C, E, H) and both (C,F,I) labyrinths of Elephas (A-C) compared with those of Elephantulus (D-F) and Procavia (G-I) in frontal view. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.m.a. anterior membranous ampulla, a.s.d. anterior semicircular duct, c.c. crus commune, c.u. common utricle, l.a. lateral ampulla, l.c. lateral semicircular canal, l.m.a. lateral membranous ampulla, l.s.d. lateral semicircular duct, m.c.c. membranous crus commune, p.c. posterior semicircular canal, p.m.a. posterior membranous ampulla, p.s.d. posterior semicircular duct, s.c. simple crus.

Figure II. 27 :

 27 Figure II.27 : Bony (A,D,G), membranous (C, E, H) and both (C,F,I) labyrinths of Elephas (A-C) compared with those of Elephantulus (D-F) and Procavia (G-I) in the plane of the anterior semicircular canal. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.c.a. anterior crista ampullaris, a.m.a. anterior membranous ampulla, a.s.d. anterior semicircular duct, a.u. anterior utricle, b.b.a.u. bony bulge for the anterior utricle, c.c. crus commune, c.u. common utricle, i.a.v. insertion of the aquaeductus vestibuli, l.c. lateral semicircular canal, m.c.c. membranous crus commune, p.c. posterior semicircular canal, p.s.d. posterior semicircular duct.

Figure II. 28 :

 28 Figure II.28 : Bony (A,D,G), membranous (C, E, H) and both (C,F,I) labyrinths of Elephas (A-C) compared with those of Elephantulus (D-F) and Procavia (G-I) in the plane of the posterior semicircular canal. Legends: a.c. anterior semicircular canal, a.m.a. anterior membranous ampulla, a.s.d. anterior semicircular duct, c.c. crus commune, c.u. common utricle, i.a.v. insertion of the aquaeductus vestibuli, l.s.d. lateral semicircular duct, m.c.c. membranous crus commune, p.a. posterior ampulla, p.c. posterior semicircular canal, p.c.a. posterior crista ampullaris, p.m.a. posterior membranous ampulla, p.s.d. posterior semicircular duct, p.u. posterior utricle.

Figure II. 29 :

 29 Figure II.29 : Bony (A,D,G), membranous (C, E, H) and both (C,F,I) labyrinths of Elephas (A-C) compared with those of Elephantulus (D-F) and Procavia (G-I) in the plane of the lateral semicircular canal. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.m.a. anterior membranous ampulla, a.s.d. anterior semicircular duct, a.u. anterior utricle, c.c. crus commune, i.a.v. insertion of the aquaeductus vestibuli, l.a. lateral ampulla, l.c. lateral semicircular canal, l.c.a. lateral crista ampullaris, l.m.a. lateral membranous ampulla, l.s.d. lateral semicircular duct, m.c.c. membranous crus commune, p.a. posterior ampulla, p.c. posterior semicircular canal, p.m.a. posterior membranous ampulla, p.s.d. posterior semicircular duct, p.u. posterior utricle, s.c. simple crus.

  Finally, the angle between the posterior and lateral canals seems to follow the same pattern of variation. It is more or less constant in Elephas maximus (from 83.2° to 88.8°), while it varies greatly in Loxodonta (it varies from 80.6° to 93.8° in L. cyclotis). It should be also noted that the measurements of these angle values are difficult to take because the canals do not always form a regular plane (they actually rarely do so). Measuring these angles manually is tricky, and it can lead to interusers variability. We tried to address this problem by using only angle values taken between the functional planes of the canals. These planes were calculated with an ARIADNE add-on, based on central streamline landmarks that we placed on the specimens. Hence, our values can somewhat differ with values taken manually and we have to be cautious when comparing these calculated values with manually taken measurements. Every angle values used during this study were obtained using the same protocol. When viewed in cross-section, the semicircular canals of extant elephants are always flattened. However, the degree of flattening is variable. In our Elephas maximus sample, the canals of MNHN.ZM.AC.2008-81 are more flattened than in the other specimens. Concerning Loxodonta, the anterior and posterior canals are more flattened in Loxodonta sp. MNHN.ZM.AC.1861-53. In L. cyclotis MNHN.ZM.AC.1950-728 and 1957.AC.1956-194, the flattening of the canals is extremely marked especially in the anterior and posterior canals. This is 110 II -Petrosal and inner ear anatomy of extant elephants the highest degree of flattening observed in our sample. Another feature showing a small variability is the thickness of the canals. The semicircular canals of extant elephants are thicker than most mammals. However, the thickness is more or less pronounced between specimens of the same genus and sometime of the same species. In Loxodonta cyclotis, some specimens display really thick canals (MNHN.ZM.AC.1961-69 and 1957-465 for instance). The thickness of the canals can also be investigated through continuous values thanks to the average thickness ratio. However, it should be noted that this ratio is calculated using the average section radius of the canal and the length of the central streamline. These measures can be slightly different depending on where the user decides to separate the slender part of the canal from the ampulla. Moreover, the ampullae in extant elephants are less defined than in most mammals which contribute to increase the variability of the delimitation. . However, in some specimens, one or several canals lack distinct undulations. For instance the anterior and posterior canals are not clearly undulated in L. africana MNHN.ZM.AC.1861-53. In Loxodonta sp. MNHN.ZM.AC.1932-523, E. maximus 2008-81 and L. cyclotis 1950-728, the lateral canal is not undulated either. For these reasons, this character will be excluded from the phylogenetic analysis. The radii of curvature display some variability in Elephas and in Loxodonta. In general, the radii of Elephas are less variable than the radii of Loxodonta. This may be explained by a more restricted data sample for Elephas (4 specimens) than for Loxodonta (8 specimens) and the fact that there are two species of Loxodonta in our sample. The radius of curvature of the anterior is the least variable in Elephas (variance of 0.02) while it is the most variable in Loxodonta (variance of 0.34). Indeed there is a difference of almost 1.8 between the largest and smallest radius in Loxodonta cyclotis. The radius of the posterior canal is less variable than the anterior in Loxodonta (variance of 0.22) but it is more variable in Elephas (variance of 0.16). Finally, the radius of the lateral canal is the least variable in Loxodonta (variance of 0.09) and it is even less variable than the radius of Elephas (variance of 0.14). The variability of the radii of curvature should be taken into account if one wants to use 111 II -Petrosal and inner ear anatomy of extant elephants these measurements in a phylogenetic analysis. It would be wrong to separate the character states in the middle of the values range of the same species (which can attain 1.8 in Loxodonta cyclotis).

  sp. MNHN.ZM.AC.2008-71 displays the smallest number of turns with two (720°) in the left ear and 1.625 (585°) in the right ear. The difference between the left and right ear of this specimen is discussed below ( § 4.2, Intra individual variability). L. africana CEB130168 displays a particularly small number of turns as well (two full turns). Hence the variability within one proboscidean species can extend to one full turn. This high degree of variability has to be taken into account while defining phylogenetic characters states. On the other hand, every specimen of Elephas and every specimen of Loxodonta lacks an apical lacuna except for L. africana CEB130168. This character is then also variable intra-specifically and should be used cautiously in phylogenetic analyses. In contrast, the relative volume of the cochlea seems to be quite constant in extant elephants. It is always around 50%of the total volume of labyrinth except for specimens of L. cyclotis MNHN.ZM.AC.1956-194 and MNHN.ZM.AC.1957-465 which display a relative volume of respectively 39.5% and 43.4%. This can be explained by the particularly high development of the semicircular canals in these two specimens. The aspect ratio of the cochlea can also vary greatly among the same genus. The cochlea of the left ear of Loxodonta sp. MNHN.AC.ZM.2008-71 displays an aspect ratio of 0.30 while it is 0.45 in Loxodonta africana MNHN.AC.ZM.1961-53. This is likely to be caused by the smaller number of turns of MNHN.AC.ZM.2008-71. However, values for the ratio are always between 0.30 and 0.45 in extant elephants and using this ratio in phylogenetic analyses remains possible if this variability is kept in mind during the definition of the characters states. In conclusion, in our studied elephant sample the petrosal and especially the bony labyrinth display a strong morphological variability, and especially a strong intraspecific variability.

4 . 3 .

 43 most spectacular example of variability that we observed among extant elephants is the difference of number of turns of the cochlea between two ears of the same Loxodonta specimen (MNHN.ZM.AC.2008-71). The left ear has 2 turns (Fig II.21K) while the right ear has 1.625 turns (Fig II.21L) which makes a difference of almost half a turn between two ears of the same individual. This condition must have been pathological as the individual was probably not hearing the same frequencies between its two ears. Our taxa sample does not allow us to analyze this condition statistically as both ears were sampled for only five proboscidean specimens (Phosphatherium PM17, Gomphotherium MNHN.F.SEP38, Stegodon FM18632, Mammuthus FM144658 and this specimen). The difference of number of turns between the two ears has been observed only in the Loxodonta specimen. However, we cannot know if this condition is rare or common among proboscideans. Constant similarities between Elephas and Loxodonta As we discussed earlier, there are no significant morphological differences between the petrosal of Elephas and of Loxodonta. Both genera display similar morphologies. Concerning the bony labyrinth, in both genera, the anterior canal is always oval and the posterior always round. The lateral canal is always the smallest one which can be seen on the reconstruction as well as in the radii of curvature. The entry point of the lateral canal into the vestibule is located at the same level which is low and close to the posterior ampulla. The secondary bony lamina is absent in both genera. The average values of the radii of curvature are quite the lateral canal). The average relative volume of the cochlea is the same between Elephas and Loxodonta (respectively 47.7% and 47%). The cochleae of both genera share similar mean aspect ratios (0.39 in both Loxodonta and Elephas). The crus commune average thickness ratio is similar between Elephas (mean value of 28.6) and Loxodonta (mean value of 30.2).

Elephasand

  Loxodonta share a lot of common characteristics, there are some differences between the two genera. The crus commune is always stocky in Elephas, while it is variable in Loxodonta. Both specimens of L. africana display a stocky crus but there is some variability in the four specimens of L. cyclotis. The mean central streamline lengths of the anterior canal of Elephas and Loxodonta are similar but it tends to be longer in Loxodonta (25.56 mm opposed to 23.84 mm in Elephas). The same can be said for the mean central streamline length of The values for the angles between canals are more constant in Elephas. Indeed the variances for the angle values in Loxodonta are 18.90 (ASC-PSC angle), 28.57 (ASC-LSC angle) and 26.48 (LSC-PSC angle) whereas they are respectively 6.90, 25.45 and 9.18 in Elephas. This difference of variability could be explained by the presence of two species among the Loxodonta sample while there is only one species in the Elephas sample. Moreover, there are only four Elephas specimens while there are eight Loxodonta specimens. The greater number of Loxodonta specimens could be the reason of the greater variance in this genus as well. The variability set aside, the mean values for each angle is very similar between Loxodonta and Elephas (respectively 78.7° and 76.1° for the ASC-PSC angle, 71.5° and 73.21° for the ASC-LSC angle and 84.7° and 85.9° for the LSC-PSC angle). In contrast, the mean value for the average thickness ratio is quite different between the two genera. The semicircular canals of Elephas tend to be thicker than those of Loxodonta (respective ratios of 4.29 and 3.62). The number of turns of the cochlea is also more variable in Loxodonta. The variance for this genus is 0.11 while it is 0.003 for Elephas. In addition to the reasons depicted earlier that could explained greater level of variance among Loxodonta, the pathological small number of turns in the right ear of MNHN.ZM.AC.2008-71 participates in the increase of variability in this genus. Hence, the average number of turns of the cochlea is higher in Elephas (2.34) than in Loxodonta (2.26). On the other hand, the total volume of the labyrinth is greater in Elephas (mean of 1250 mm 3 ) than in Loxodonta (mean of 1148 mm 3 ).

  semicircular duct system of an extant elephant is here reconstructed in 3D for the first time using CT scan methods. The semicircular ducts of Elephas are strikingly thin compared to its semicircular canals. specimens of the same species show some level of intraspecific variability and even intraindividual variability (number of turns of the cochlea). The investigation of the variability allows refining the definition of petrosal and labyrinth phylogenetic characters.

  first chapter focuses on the two earliest-known elephant relatives (Eritherium, 60 Myo and Phosphatherium, 55 Myo) and helps characterizing the ancestral morphotype of Proboscidea and Afrotheria. The second chapter focuses on the ear region of extant elephants and provides some information about its variability at low taxonomic level. Even though the inner ear of other proboscidean fossils has already been investigated (Numidotherium and Moeritherium in Court, 1992 and Benoit et al. 2013b; an unknown elephantimorph in Ekdale, 2011), we lack information about the inner ear anatomy of most proboscidean lineages. Indeed, the Proboscidea is a diversified order that contains over 170 extinct species with very different morphologies. This clade is surprisingly well-documented, with known fossil covering almost its entire range of existence and found in every continent except Antarctica and Australia. The objective of Chapter III is to study the anatomy of the petrosal and inner ear of several fossil proboscideans in the perspective of tracing the evolution of this complex and methods'). On the other hand, the ear region of an unpublished early embrithopod (from the Ouled Abdoun basin, Morocco) has been investigated as well during this work and used for comparisons. A more detailed anatomical study of the early afrotherian

  were investigated. The specimen is of Selandian age (ca. 59-60 Ma) and comes from the Sidi Chennane quarries (Ouled Abdoun basin, Morocco). Both petrosals were scanned in Gheerbrant et al. with several other diagnostic cranial fragments of the same individual which documents a new primitive embrithopod. This material was found in early Ypresian phosphates beds of the Ouled Abdoun basin, Morocco (Gheerbrant et al 2003), and it is currently under study (in progress, E. Gheerbrant pers. comm. 2016). Only a very small part of the cochlea is preserved, the slender semicircular canals are quite complete (only a part of the lateral canal is broken)

  from the late early Eocene of El Kohol in Algeria. Two specimens of N. koholense were investigated during this PhD thesis. First, the microtomographic slices of the unreferenced isolated petrosal described in Court & Jaeger (1991) and segmented in Benoit et al. (2013b) have been reinvestigated. As this specimen was described in details in previous publications we only used it for comparisons with other proboscideans. We applied the same measuring protocol using 3D landmarks to this specimen for adequate comparisons. We then CTscanned the ear region of another specimen (UOK5) of N. koholense that consists of a mineralized and almost complete skull. Moeritherium Three specimens of Moeritherium C.W. Andrews, 1901 have been studied. First, the rather complete skull MNHN.F.LBE1 displaying the natural endocast of the bony labyrinth was investigated. This skull was found by Arambourg and Magnier (1961) in the Eocene deposits of Dor el Talha (Libya). It 121 III -Anatomy of the ear region of fossil proboscideans has been attributed to the species Moeritherium lyonsi Andrews, 1901 but this determination is doubtful so we will refer to it as Moeritherium cf. lyonsi. Some features of the cochlea and the semi-circular canals can be seen with the naked eye on this specimen. However, the high degree of mineralization prevented us from any further CT scan acquisition which would have allowed us to access the other half of its bony labyrinth. Secondly, an isolated petrosal of Moeritherium trigodon Andrews, 1904 (SMNS 47789-90) has been CT-scanned. It belongs to the collections of the Natural History Museum of London (NHMUK 68436) and has been found in the Idam Unit of Dor el Talha

  poorly contrasted and the segmentation was extremely difficult. Hence the 3D model is imprecise and some features are really difficult to describe properly. Finally, the third specimen also belongs to the species Moeritherium lyonsi. It belongs to the Stuttgart Museum für Naturkunde (SMNS 47789-90) and consists of a part of the basicranium still bearing a fraction of the petrosal. This specimen is extremely incomplete but in contrast with other studied specimens (MNHN.F.LBE1, NHMUK 68436) of Moeritherium, it shows a particularly low level of mineralization. Unfortunately, the CT-scan acquisition showed that only a small part of the semicircular canals is preserved in this specimen. The cochlea and vestibule are completely missing. Prodeinotherium Three specimens attributed to Prodeinotherium bavaricum von Meyer, 1831 were studied. They all belong to the collections of the Muséum d'Histoire Naturelle de Toulouse and are labelled MHNT.PAL.2013.01108A and 01108E and Beon 98 E1 3049. They consist of fragmentary parts of the basicranium found in Montréal-du-Gers (France). Mammut Two petrosals of Mammut americanum Kerr, 1792 were studied. They both belong to the collections of the AMNH and are numbered FM14293. However, they have a very different aspect and color. Even though they are left and right petrosals, they belong from different individuals. This is confirmed with the segmentation, showing different semicircular canals morphologies. Hence, we chose to number them FM14293A (left petrosal) and FM14293B (right petrosal) to distinguish them. The cochlear part of FM14293-A is preserved, however the petrosal was cut off at the level of the cochlea a few years ago for investigation. Therefore, the bony cochlea can be seen with naked eye on the specimen. On the other hand, the cochlear part of FM14293-B is completely missing. MNHN.F.SEP38) and one female (MNHN.F.SEP18) -were CT scanned with access to both left and right ears. They come from the Miocene fossil deposit of En-Péjouan located on the territory of Simmore (Gers, France). Both petrosals and inner ear of MNHN.F.SEP38 were segmented. However, poor contrasting resulting from a strong mineralization of MNHN.F.SEP18 prevented us from obtaining a clear virtual cast. Therefore only part of the inner ears of this specimen was segmented and the petrosals were left unstudied. An isolated petrosal of a juvenile Gomphotherium angustidens from the collections of the Muséum d'Histoire Naturelle de Toulouse (CBar coll V. 2) was also CT scanned. It comes from a Miocene fossil deposit located in Castelnau-Barbarens (Gers, France) and it was entirely segmented (petrosal and inner ear). Cuvieronius An isolated petrosal of Cuvieronius sp. Osborn, 1923 (FM103247) was studied. It belongs to the collections of the AMNH and has not been attributed to any species of Cuvieronius. The specimen has been excavated in the Matthews Wash Locality, Graham County, Arizona (USA). Its cochlear part is broken but the specimen shows a low degree of mineralization so the segmentation of the semicircular canals was rather easy. both belong to the collections of the AMNH and have specimen number FM21807. They have been excavated in the Curtis Ranch locality, Cochise County, Arizona (USA). The first specimen numbered here FM21807-A is a left petrosal. It is quite 123 III -Anatomy of the ear region of fossil proboscideans damaged and the bony labyrinth is not entirely preserved. The labyrinth has been filled with sediments during the fossilization before the petrosal was broken. Therefore, a natural endocast of a part of the cochlea and a part of the anterior and posterior semicircular canals shows on the tympanic surface of the petrosal. The lateral semicircular canal is completely missing. The second specimen FM21807-B lacks the cochlear part but all three canals are preserved. Platybelodon First, a skull of Platybelodon grangeri Osborn, 1929 (26564 824+, AMNH collections) has been CT-scanned. It comes from the Platybelodon Quarry locality that belongs to the Tung Gur formation deposits (Mongolia) of Pliocene age. This specimen is damaged, distorted and mineralized. It was not possible to identify its inner ears on the microtomographic slices. Therefore a cranial fragment belonging to the same specimen and associated with a sedimentary matrix was CT-scanned. It was suspected to be an isolated petrosal, which was confirmed by the study of the microtomographic slices despite the high degree of mineralization. Anancus Seven isolated petrosals of Anancus arvernensis Croizet & Jobert, 1828 from the Pliocene fossil deposit of Dorkovo (Pazardjik, Bulgaria) have been sampled. They all belong to the National Museum of Natural History of Sofia (they are labelled NMNHS.FM2991A to G). Each of these specimens was CT-scanned and the inner ears have been segmented successfully. Stegodon The left and right petrosals of the quite complete skull FM18632 (collections of the AMNH) of a juvenile Stegodon orientalis Owen, 1870 were studied. The specimen was excavated in Wan-hsien, Sze-chuan (China). The specimen is quite mineralized but it was possible to segment both ears. The cochlear part of the petrosal has been preserved in both ears. CT scanned. In addition, the left and right petrosals of specimen FM 144658 of Mammuthus columbi Falconer, 1857 from the collection of the American 124 III -Anatomy of the ear region of fossil proboscideans Museum of Natural History were studied. The cochlear part of the petrosal was missing in both of them but their vestibular part has been successfully segmented. Palaeoloxodon The isolated left petrosal of specimen M82706 of Palaeoloxodon antiquus Falconer & Cautley 1847 was studied. It belongs to the collections of the Natural History Museum of London (NHMUK). This specimen comes from the Pleistocene deposits of the Sandy Lane Quarry (Essex, United Kingdom). It is a rather complete individual which skull is broken in many fragments. Amongst the skull fragments, a single broken petrosal which cochlear part was missing was identified. This fragment was CT-scanned and the semicircular canals were segmented.

  Ocepeia daouiensisThe whole basicranium of Ocepeia daouiensis has been CT-scanned and it is still bearing both petrosals. While the petrosal is damaged in the mastoid region, the part containing the inner ear is well preserved. Since there are no significant differences between the left and the right ear, the measurements given below are an average of the left and right ears measurements. Only the bony labyrinth of Ocepeia will be discussed, as the petrosal was already detailed in[START_REF] Gheerbrant | Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal[END_REF]. The total volume of the inner ear of Ocepeia is 17.53 mm 3 (Table

( 2 .

 2 18) is very close to the ratio of the anterior canal (2.22). The radius of curvature of the posterior canal is 1.55. The lateral semicircular canal is oval. The estimated length of the central streamline and the average section radius are similar to the other canals. The thickness ratio is slightly lower (2.04) for the lateral canal than for the anterior and posterior canals.

Figure III. 1 :

 1 Figure III.1 : 3D reconstructed model of the left bony labyrinth of Ocepeia daouiensis PM45 in anterior canal (A), posterior canal (B), lateral canal (C), frontal (D) and cochlear (E) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, c.ca. cochlear canaliculus, co cochlea, f.c. fenestra cochleae, f.v. fenestra vestibuli, he helicotrema, l.a. lateral ampulla, l.c. lateral semicircular canal, mo modiolus, p.a. posterior ampulla, p.c. posterior semicircular canal.

  and posterior canals and the angle between the lateral and posterior canals are more or less right (respectively 91.5° and 87.8°). The angle between the anterior and lateral canals is smaller (80.1°). The radius of curvature of the lateral canal is smaller than those of the anterior and posterior canals. The anterior canal is the largest one and the posterior canal has a medium radius of curvature. The smaller size of the lateral canal is obvious on the reconstruction (Fig III.1C and III1.D). The anterior canal apex is located slightly higher than the posterior canal apex. The semicircular canals of Ocepeia are noticeably thin with an average thickness ratio of 2.15. In crosssection, the canals appear to have a rather circular shape. The slender part of the lateral semicircular canal is connected to the vestibule at a quite high position.

is 2 .

 2 125 (765°). In ventral view (Fig III.1E), the axis for the modiolus is very loose and there is a marked visible lacuna. The basal turn of the cochlea is only partially overlapped by the apical turn and is still visible in ventral view. The lamina secundaria is present on the first half-turn and is shallow. The volume of the cochlea is 11.65 mm 3 which represents around two thirds of the total volume of the bony labyrinth.

  outline is still observable (Fig III.2B). It has the shape of a latero-medially elongated ellipse. The outline of the foramen acusticum inferior and superior is not visible as both structures are not preserved. The meatus is bordered by a thick prefacial commissure. The subarcuate fossa is located posterolaterally to the meatus and is moderately deep and broken. The aquaeductus vestibuli has the shape of a thin slit that opens in the lateral side of the petrosal.

Figure III. 2 :

 2 Figure III.2 : Reconstructed 3D model of the petrosal (A-D) and bony labyrinth (E-H) of PM53. (A) Medial view (B) Tympanic view (C) Cerebellar view (D) Lateral view (E) Frontal view (F) Anterior canal view (G) Posterior canal view (H) Lateral canal view. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea, i.a.m. internal auditory meatus, l.a. lateral ampulla, l.c. lateral semicircular canal, l.s. lamina secundaria, p.a. posterior ampulla, p.c. posterior semicircular canal, pr promontorium, s.f. subarcuate fossa, ve vestibule

Numidotherium

  have already been described in the literature. In[START_REF] Court | Anatomy of the periotic bone in the Eocene Proboscidean Numidotherium koholense : An example of parallel evolution in the inner ear of tethytheres[END_REF], the petrosal bone is studied and compared with other tethytheres. In[START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF], a natural cast of a left cochlea is described. Finally, the first study of the labyrinth of Numidotherium using microtomographic methods is carried out byBenoit et al. (2013b). However, the bony labyrinth of Numidotherium has never been fully segmented as the specimen studied byBenoit et al. is incomplete. Here we will describe the first complete 3D model of a bony labyrinth of Numidotherium and compare it with the other studied specimens. The specimen studied is a rather complete skull belonging to a Numidotherium koholense specimen (UOK5). Given the large size of the skull, the ear region was scanned at a rather low resolution (81.66 µm).Moreover, the advanced mineralization of the specimen leads to a poor contrast in the average section radii, given by the ARIADNE addon that is currently developed by Romain David, have, for instance, to be taken with caution.

Figure III. 3 :

 3 Figure III.3 : Reconstructed 3D model of the bony labyrinth of Numidotherium koholense UOK5 in anterior canal (A), posterior canal (B), lateral canal (C), frontal (D) and cochlear (E) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, c.c. crus commune, co cochlea, l.a. lateral ampulla, l.c. lateral semicircular canal, p.a. posterior ampulla, p.c. posterior semicircular canal.

is 4 .

 4 5 mm and its average section radius 0.67 mm. The anterior and posterior canals meet quite high (approximately 75% of the height of the anterior canal) and the crus commune is not inclined as in the specimen described in Benoit et al. (2013b).

  we used. Indeed, the development of the software ARIADNE shows that classical measurements of the radius of curvature tend to underestimate this value. The posterior semicircular canal is slightly oval but less clearly than in the unlabeled specimen described in Benoit et al. (2013b). The major axis of the canal forms an angle of 22° with the crus commune. A similar value is found in the other specimen (25°). The central streamline length of the posterior canal is 14.79 mm which is slightly longer than for the anterior canal. This is close to the estimated value given in Benoit et al. (2013b). Hence we support their assumption that the posterior canal is longer than the anterior canal. The average section radius of the posterior canal is slightly smaller than the anterior one (0.30 mm). Hence the thickness ratio of the posterior canal (2.02) is smaller than the ratio of the anterior canal. The estimated radius of curvature of the posterior canal is slightly smaller than the radius of the anterior canal (3.28). This is very close to the estimated value (3.21) given by Benoit et al. (2013b). The lateral semicircular canal is round in this specimen and the unlabeled specimen described by Benoit et al. (2013b). The central streamline length of this canal (13.89 mm) is identical to the anterior canal length. In the specimen described in Benoit et al. (2013b), the lateral canal was too damaged to estimate its length. The average section radius of the lateral canal is close to that of the other canals (0.29 mm) and the thickness ratio (1.99) is close to the ratio of the anterior canal. The radius of curvature of the lateral canal is clearly the smallest with a value of 2.56. It is slightly larger than the measurement estimated by Benoit et al. (2013b) for the other specimen (2.46) but nonetheless very close. The functional planes of the anterior and posterior canals form an angle of 78.23°. This value is close to the angle measured by Benoit et al. (2013b) on the unlabeled specimen (75°). The angle between the anterior and lateral canals is similar but slightly more acute (75.5°). This differs with the estimation given by Benoit et al. (2013b) which is more obtuse (82°) than for the anterior canal. However, the value found for the angle between the posterior and lateral canals (96°) supports the estimation given by Benoit et al. (2013b) for the other specimen which indicates a larger value for this angle (92°). It appears that this angle is clearly more obtuse in both specimens. In UOK5 and the unlabeled specimen, we find the same pattern of radii of curvature. The anterior and the posterior canals have quite similar radii while the lateral canal is clearly smaller. The anterior canal is always slightly bigger than the posterior canal, a condition even more marked within our study (there is a difference of 0.23 between the two radii while the difference is only of 0.06 in Benoit et al. 2013b). As it is pointed out in their study, the lateral canal is the smallest one but it is proportionally larger than the lateral canal of extant elephants that display a relatively smaller canal. The anterior canal apex is located slightly higher than the posterior canal apex. As observed in Benoit et al. (2013b), the canals are more slender than the canals of Moeritherium and Elephantimorpha. It is approximately as thick as the canals of Phosphatherium and thicker than the canals of Eritherium. These observations are confirmed by the values of the average thickness ratio (2.16 in Numidotherium, 2.09 in Phosphatherium, 1.07 in Eritherium). The anterior and posterior canals appear to be circular in crosssection. The lateral canal seems to be slightly flattened but this could be due to the imprecise segmentation. The slender part of the lateral semicircular canal is connected to the vestibule at a quite high position. As a result, there is a partial fusion of the bony lateral canal with the posterior canal and ampulla. This structure is generally referred to as secondary common crus. However, contrary to the crus commune, the membranous lateral and posterior ducts are never fused

  the secondary common crus is only a character of the ossification resulting from the proximity of the posterior and lateral canals. This proximity can be caused by several factors (expansion of the lateral canal, of the posterior canal…) and therefore its homology between taxa is not verified. No ridges were observed on the specimen UOK5 nor on the unlabeled specimen studied in Benoit et al. (2013b). The anterior canal displays an undulation contrary to the other two canals.

  UOK5 with the cochlea of the previously published specimens. The cochlea completes only one and a half turns (Fig III.3E) as the specimen described by Court(1992), while the unlabeled specimen described byBenoit et al. (2013b) completes 1.62 turns. The aspect ratio is 0.48 which is close to the values calculated for the other specimens (0.52 in[START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF] 0.51 in Benoit et al. 2013b). The cochlear coiling is indeed rather planar.The helecotrema is quite large and our specimen bears a small apical lacuna as the unlabeled specimen described inBenoit et al. (2013b). There are no traces of a lamina secundaria on this specimen and on the specimen described byBenoit et al. (2013b). However, this structure is clearly present in the specimen described by[START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF]. We can assume that the poor resolution prevents us from observing the furrow for the lamina secundaria. The cochlear volume (35.06 mm 3 ) represents around 42% of the total volume of the bony labyrinth which is close to the values found byBenoit et al.

  highly mineralized which prevented from recovering a clear 3D model. Hence, the obtained 3D model is not well detailed and not suitable to any geometric morphometric analysis. Secondly, a basicranium of Moeritherium lyonsi from the Stuttgart Museum für Naturkunde (SMNS 47789-90) has been CT-scanned. Contrary to the London specimen, the Stuttgart specimen is not mineralized and the labyrinth remains unfilled. However, only fragments of two semicircular canals are preserved. In this section, we nonetheless present the few anatomical features of the labyrinth that are observed in both specimens and we compare them based on previous descriptions. Vestibular bony labyrinth Ampullae It is difficult to judge of the ampullae definition in specimen NHMUK 68436 given the poor quality of the reconstruction but they seem to be quite well-defined (Fig III.4), by contrast to modern elephants which display poorly defined ampullae.

Figure III. 4 :

 4 Figure III.4 : Reconstructed 3D models of the petrosal of Moeritherium 68436 in cerebellar (A) and posteromedial (B) views. Reconstructed 3D models of the bony labyrinths of specimen 68436 in frontal (C), anterior canal (D), posterior canal (E), lateral canal (F) and cochlear (G) views and of specimen SMNS 47789-90 in frontal (H) and anterior canal (I) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea, he helicotrema, i.a.m. internal auditory meatus, l.a. lateral ampulla, l.c. lateral semicircular canal, p.c. posterior semicircular canal, p.f. perilymphatic foramen, ppc posterior paratympanic cavity, pr promontorium, prot protuberance, s.f. location of the subarcuate fossa.

(

  MHNT.PAL.2013.01108E) is quite damaged. Its morphology is very close to the morphology of extant elephants, with the dorsal view separated in two different surfaces (the cerebellar and cerebral surfaces). The cerebellar surface is shattered as well as the internal auditory

Figure III. 5 :

 5 Figure III.5 : Reconstructed 3D models of the petrosal of Prodeinotherium bavaricum MHNT.PAL.2013.01108E in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.p.p. crista partis petrosa, i.a.m. internal auditory meatus, p.f. location of the perilymphatic foramen, pr promontorium, t.t. tegmen tympani.

Figure III. 6 :

 6 Figure III.6 : 3D reconstructed models of the bony labyrinths of Prodeinotherium bavaricum MHNT.PAL.2013.01108E (A-E) and unknown rhinocerotids isolated petrosals previously assigned to Prodeinotherium MHNT.PAL.2013.01108A (F-J) and Beon 98 E1 3049 (K-N) in frontal (A, F, K), anterior canal (B, G, L), posterior canal (C, H, M), lateral canal (D, I, N) and cochlear (E, J) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, c.ca. cochlear canaliculus, co cochlea, f.c. fenestra cochleae, he helicotrema, l.a. lateral ampulla, l.c. lateral semicircular canal, p.a. posterior ampulla, p.c. posterior semicircular canal.

  Figure III.7 : 3D reconstructed models and drawings of the petrosal of Mammut americanum FM14293A in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.F. aquaeductus Fallopii, a.t. apical turn of the cochlea, a.v. aquaeductus vestibuli, b.t. basal turn of the cochlea, c.p.p. crista partis petrosa, i.a.m. internal auditory meatus, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal (part of), t.t. tegmen tympani.

Figure III. 8 :

 8 Figure III.8 : 3D reconstructed models and drawings of the petrosal of Mammut americanum FM14293B in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.p.p. crista partis petrosa, i.a.m. internal auditory meatus, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal (part of), t.t. tegmen tympani, ty tympanohyal.

  In FM14393-A, a vertical ridge runs on the crus commune in the extension of the posterior semicircular canal ridge associated with a well-marked bulge. In FM14393-B, the vertical ridge is present as well as a less pointy bulge. The average section radius of the crus commune of Mammut is 1.18 in FM14393-A and 1.55 mm in FM14393-B. The length of the crus commune is approximately 7.74 in FM14393-A and 7.21 mm in FM14393-B. Therefore the specimens have a crus commune with a thickness ratio of 15.24 (FM14393-A) and 21.55 (FM14393-B). In FM14393-A, the anterior and posterior semicircular canals meet quite low (approximately at the mid-height of the anterior canal) while they meet higher in FM14393-B (approximately at two thirds of the height of the anterior canal). The crus commune is not inclined on both specimens.

  FM14293-A, it forms an even bigger angle in FM14293-B (36°). The anterior semicircular canal appears more slender in FM14293-A than in FM14293-B. Indeed the central streamline of the anterior canal is longer in FM14293-A (28.81 mm) than in FM14293-B (23.58 mm). The average section radius of the anterior canal of Mammut is 0.95 mm in FM14393-A and 1.01 mm in FM14393-B. Therefore, the thickness ratio of this canal is 3.30 in FM14393-A and 4.30 in FM14393-B. The anterior canal radius of curvature is 6.33 in FM14293-A and 5.43 in FM14293-B. The posterior semicircular canal is oval in both FM14293-A and FM14293-B. The major axis of the canal forms an angle of 5° with the crus commune in both specimens which is clearly less than the angle of the anterior canal. The central streamline length of the posterior canal is 25.54 mm in FM14293-A and 23.79 mm in FM14293-B.

Figure III. 9 :

 9 Figure III.9 : 3D reconstructed models of the bony labyrinths of Mammut americanum FM14293A (A,B,D,F,H) and FM14293B (C,E,G,I) in cochlear (A), anterior canal (B-C), posterior canal (D-E), frontal (F-G) and lateral canal (H-I) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, c.ca. cochlear canaliculus, co cochlea, f.c. fenestra cochleae, f.v. fenestra vestibuli, he helicotrema, l.a. lateral ampulla, l.c. lateral semicircular canal, mo modiolus, p.a. posterior ampulla, p.c. posterior semicircular canal, p.f. perilymphatic foramen. While the value is very similar with the anterior canal value in FM14293-B, there is a difference of more than 3 mm in FM14293-A. The average section radius of the posterior canal is very similar to the anterior one (0.95 mm in FM14393-A and 1.04 mm in FM14393-B). The thickness ratio of this canal is very close to the anterior ratio in FM14293-B (4.36) and slightly higher in FM14393-A (3.70). The radius of curvature of the posterior canal

  The petrosal is very similar to the petrosal of extant elephants(Fig III.10 and III.11), with the dorsal part consisting of two surfaces. Contrary to the description of[START_REF] Tassy | L'anatomie cranio-mandibulaire de Gomphotherium angustidens (Cuvier, 1817) (Proboscidea, Mammalia) : données issues du gisement d'En Péjouan (Miocène moyen du Gers, France)[END_REF], we found that the crista partis petrosa is very sharp in SEP38.However it is blunt in Cbar coll.V 2 in which the tegmen tympani is broken. The groove for the middle meningeal artery is deep and it meanders upon the surface of the tegmen tympani in SEP38. The cerebellar surface that normally bears the subarcuate fossa is slightly convex in SEP38 and concave in Cbar coll.V 2. The internal auditory meatus is oriented anteriorly as every other studied elephantimorphs. The vestibular aqueduct is oriented postero-ventrally in SEP38 and has the aspect of a thin slit. However, it is oriented posteriorly in Cbar coll.V 2 and has a rounder shaper. In posterior view, the vestibular aqueduct is clearly ventral in SEP38 but more centered in Cbar coll.V 2. The stapedial ratio is 1.5 for both specimens.

Figure III. 10 :

 10 Figure III.10 : 3D reconstructed models of the petrosal of Gomphotherium angustidens CBar coll. V2 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.p.p. crista partis petrosa, i.a.m. internal auditory meatus, p.f. perilymphatic foramen, pr promontorium, t.t. tegmen tympani.

Figure 11 :

 11 Figure 11 : 3D reconstructed models and drawings of the petrosal of Gomphotherium angustidens MNHN.F.SEP38 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.F. aquaeductus Fallopii, a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal (part of), t.t. tegmen tympani, ty tympanohyal.

Figure III. 12 :

 12 Figure III.12 : 3D reconstructed models of the bony labyrinths of Gomphotherium angustidens specimens CBar coll. V2 (A-E) and MNHN.F.SEP38 left (F-J) and right (K-O, mirrored) sides in frontal (A,F,K), anterior canal (B,G,L), posterior canal (C,H,M), lateral canal (D,I,N) and cochlear (E,J,O) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea, f.v. fenestra vestibuli, he helicotrema, l.a. lateral ampulla, l.c. lateral semicircular canal, mo modiolus, p.a. posterior ampulla, p.c. posterior semicircular canal, p.f. perilymphatic foramen.

Figure III. 13 :

 13 Figure III.13 : 3D reconstructed models and drawings of the petrosal of Cuvieronius sp. FM103247 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.F. aquaeductus Fallopii, a.v. aquaeductus vestibuli, c.p.p. crista partis petrosa, gr groove of the cerebral surface, i.a.m. internal auditory meatus, p.m. pars mastoidea (broken), pr promontorium, s.c. stylomastoid canal (part of), t.t. tegmen tympani, v.c. vascular canal.

(

  Fig III.13). In cerebellar view, the aquaeductus vestibuli has the aspect of a thin slit and is located in the posterior part of the petrosal. It is, however, more centered than in most extant elephants.The region bearing the internal auditory meatus is broken but its location is clearly visible. It is oriented antero-posteriorly.The epitympanic wing is completelybroken. There is no trace of a subarcuate fossa and the crista partis petrosa is very blunt. Along the crista runs a semienclosed vascular canal (v.c. in Fig III.13C).It is distinct on the petrosals in some parts but it is totally enclosed in others. This canal probably housed a blood vessel but it seems to exist only in Cuvieronius, as it has not been described in any other examined proboscideans. The angle between the cerebellar and cerebral surface of the petrosal is right (90°). In cerebral view, the tegmen tympani is rather well preserved, but its anterior part is broken. There is a thin and shallow groove running almost parallel to the crista partis petrosa that probably housed the superior petrosal sinus. A larger groove lies in the posterior part of the tegmen tympani. This is probably the groove for the middle meningeal artery but this feature is not well defined. In tympanic view, the petrosal is quite damaged.The promontorium is completely broken making the observation of the fenestrae impossible.The aquaeductus Fallopii is preserved. It consists of a deep sulcus which presents the same location and orientation as in extant elephants. The sulcus is not covered by a bony roof but it could have been broken after the death of the animal.The fossa for the stapedius muscle is well preserved and lies medial to the aquaeductus Fallopii (at the supposed level of the perilymphatic foramen).Between the fossa and the aquaeductus Fallopii lies a deep cavity that is probably a broken pneumatic cell of the pars mastoidea. In this view, it is clear that the anterior part of the tegmen tympani is missing.Inner earSince the cochlear part of the petrosal is broken on the scanned Cuvieronius specimen, the cochlear part of the bony labyrinth could not be segmented. Hence the total volume of the bony labyrinth is unknown.Vestibular bony labyrinthAmpullaeThe ampullae of Cuvieronius appear less defined like most modern proboscideans. The ampulla of the lateral semicircular canal shows a bump on its common part with the anterior semicircular canal ampulla (Fig III.14).

(

  not stocky as in Elephas 1904-273 for example) and displays a slight basal thickening. A bump is located on the posterior part of the crus commune near the insertion of the lateral semicircular canal into the vestibule. The average section radius of the crus commune of Cuvieronius is 1.65 mm and its length is approximately 9.52 mm. Therefore the specimen of Cuvieronius has a crus commune with a thickness ratio of 17.39. The anterior and posterior semicircular canals meet quite high (approximately at 75% of the height of the anterior canal) and the crus commune is slightly inclined towards the anterior canal.Semicircular canalsThe anterior semicircular canal is oval. Its major axis forms an angle of 28° with the crus commune. The central streamline length of the anterior canal is 25.02 mm and the average section radius is 0.85 mm. Therefore, the thickness ratio of this canal is 3.41. Its radius of curvature is particularly large(6.18).

Figure III. 14 :

 14 Figure III.14 : 3D reconstructed model of the bony labyrinth of Cuvieronius sp. FM103247 in frontal (A), anterior canal (B), posterior canal (C) and lateral canal (D) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, l.a. lateral ampulla, l.c. lateral semicircular canal, p.a. posterior ampulla, p.c. posterior semicircular canal

  crus commune is elongated in the left ear but appears stockier in the right one; this can be due to the conditions of preservation of the right petrosal. There is no marked basal thickening at the basis of the crus commune. The crus commune is quite smooth and does not display any bulge and ridges. The average section radius of the crus commune of Stegomastodon is 1.66 mm. The values given are only from the left ear which is the only one wellpreserved. The length of the crus commune is approximately 7.25 mm. Therefore this specimen has a crus commune with a thickness ratio of 32.33. In both ears, the anterior and posterior semicircular canals meet quite high, approximately at three quarters of the height of the anterior canal. The crus commune is not inclined.

Figure III. 15 :

 15 Figure III.15 : 3D reconstructed models and drawings of the left petrosal of Stegomastodon sp. FM21807 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.c. natural cast of the anterior semicircular canal, a.F. aquaeductus Fallopii (location), a.v. aquaeductus vestibuli, c.p.p. crista partis petrosa, co natural cast of the cochlea, gr groove of the cerebral surface, i.a.m. internal auditory meatus, p.c. natural cast of the posterior semicircular canal, p.f. perilymphatic foramen, p.m. pars mastoidea (broken), pr promontorium, s.c. stylomastoid canal (part of), t.t. tegmen tympani (broken), v.c. vascular canal.

Figure 16 :

 16 Figure 16 : 3D reconstructed models and drawings of the right petrosal of Stegomastodon sp. FM21807 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.p.p. crista partis petrosa, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, p.f. perilymphatic foramen, p.m. pars mastoidea (broken), pr promontorium, t.t. tegmen tympani (broken).

Figure 17 :

 17 Figure 17 : 3D reconstructed models of the left (A,B,D,F,H) and right (C,E,G,I, mirrored) bony labyrinths of Stegomastodon sp. FM103247 in cochlear (A), anterior canal (B,C), posterior canal (D,E), frontal (F,G) and lateral canal (H,I) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea, he helicotrema, i.a.v. insertion of the aquaeductus vestibuli, l.a. lateral ampulla, l.c. lateral semicircular canal, p.a. posterior ampulla, p.c. posterior semicircular canal, p.f. perilymphatic foramenSemicircular canalsThe anterior semicircular canal is oval in both right and left ears of FM21807. The major axis of the canal forms an angle of 48° with the crus commune in the left ear but the angle is lower in the right ear (31°). Because of the swollen aspect of the right ear canals that does not seem to be natural, their measurements and thickness will not be discussed. On the other hand, the left ear

  cochlear part is only preserved in the left ear. The cochlea displays 2 turns (720°) and a length of 65.8 mm. In ventral view, the modiolus is completely overlapped by the apical turn and there is no visible apical lacuna. The basal turn of the cochlea is only partially overlapped by the apical turn and is still visible in ventral view. The lamina secundaria is absent. The cochlea is planispiral with an aspect ratio of 0.45. . The inner ear is filled with sediment that has grey values similar to the bone. Therefore, the 3D model obtained after segmentation is a bit imprecise. Moreover, it was not possible to segment the petrosal as its limits with other bones and sediment were not visible. The only visible parts of the petrosal are the external ones which consist of parts of the cerebral and cerebellar surfaces. The angle between the cerebral and cerebellar surfaces is obtuse (105°). In cerebral view, a shallow groove is visible and is probably the groove for the middle meningeal artery. It is more or less parallel to the crista partis petrosa which is sharp. In cerebellar view, no structures are really recognizable.

  Gomphotherium. Again, the poor level of contrast prevents us from observing the potential ridges of the crus commune. In addition, numerical values like the average section radius have to be taken with caution as the segmentation of this specimen is imprecise. With all these factors in mind, we can continue the description of the bony labyrinth of Platybelodon. The average section radius of the crus commune is 1.17 mm and its length is 4.20, which gives a quite high average thickness ratio(27.92). The anterior and posterior semicircular canals meet quite low (approximately at the midheight of the anterior canal) and the crus commune is not inclined.Semicircular canalsThe overall shape of anterior semicircular canal is oval. The major axis of this canal forms an angle of 30° with the crus commune. The central streamline length is 22.02 mm and the average section radius of the canal is 0.81 mm. Therefore, the average thickness ratio of III -Anatomy of the ear region of fossil proboscideans the canal is 3.69. The radius of curvature of the anterior canal is 5.16. On the contrary, the posterior semicircular canal is round. Its central streamline length is basically the same as the anterior canal (22.00 mm) but its average section radius is lower (0.65 mm) which gives the posterior semicircular canal of Platybelodon a lower average thickness ratio than its anterior canal (2.93). However it is hard to see a difference of thickness between this canal and the anterior canal.

Figure III. 18 :

 18 Figure III.18 : 3D reconstructed models of the left bony labyrinth of Platybelodon grangeri 26564 (824+) in anterior canal (A), posterior canal (B), lateral canal (C), frontal (D) and cochlear (E) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, c.c. crus commune, co cochlea, l.a. lateral ampulla, l.c. lateral semicircular canal, p.a. posterior ampulla, p.c. posterior semicircular canal

  However, in some specimens such as NMNHS.FM2991A, C, E and G, the trace of the mastoid pneumatic cells is still visible on the petrosal. The aquaeductus Fallopii is also preserved in several specimens. It is not covered by bone roofs as in extant elephants, however these structures could have been lost during the taphonomic process. Vestibular bony labyrinth (Fig III.26-30) Ampullae As in all proboscideans except the earliest ones such as Eritherium and Phosphatherium, the ampullae of Anancus appear less defined. On NMNHS.FM2991B a sharp ampullar ridge is visible on the lateral canal. It extends from the basis to the apical part of the lateral ampulla. The ampullar ridge maximum height is located at the center of the ampulla; it has the shape of a flattened bump. Although no other specimen displays such type of ridge, some of them show a slight ridge on their lateral ampulla. It is the case of NMNHS.FM2991A, NMNHS.FM2991C, NMNHS.FM2991D and NMNHS.FM2991G.At the limit between the posterior ampulla and the vestibule, there is a highly marked bulge in NMNHS.FM2991F. It is small but high and has the appearance of a wart. so it is an intra-specific variable character as the other ridges and bulges.III -Anatomy of the ear region of fossil proboscideansCrus communeThe crus commune of Anancus is elongated in all specimens and never displays a strong basal thickening. Some specimens of Anancus display a more or less sharp ridge on their crus commune. This feature is not visible on all specimens of Anancus and it takes different shapes from specimen to specimen. In NMNHS.FM2991A, the ridge is rather sharp and extends from the posterior canal to the basis of the lateral canal ampulla. This structure creates two slightly concave planes on either sides of the ridge. In NMNHS.FM2991B, a ridge extends on the crus commune from the posterior semicircular canal to a bulge on the vestibule. A similar morphology is found in NMNHS.FM2991G but the ridge is clearly less marked in this specimen. In NMNHS.FM2991C, no ridge is visible on the crus commune. NMNHS.FM2991D displays a ridge similar to the one of NMNHS.FM2991A but clearly less sharp. In NMNHS.FM2991E the ridge is present and extends only from the posterior canal to the basis of the crus commune. The ridge is absent in NMNHS.FM2991F. The thickness of the crus commune is variable. It is particularly thin in NMNHS.FM2991B, NMNHS.FM2991F and NMNHS.FM2991G with respective thickness ratios of 20.05, 18.42 and 20.33. In NMNHS.FM2991A, the anterior and posterior semicircular canals meet quite low (approximately at the midheight of the anterior canal) while they meet higher in the other specimens (approximately at two thirds of the height of the anterior canal). The crus commune is slightly inclined in NMNHS.FM2991A but the angle of inclination is even higher in NMNHS.FM2991B. The crus commune is vertical in the other specimens.

Figure III. 19 :

 19 Figure III.19 : 3D reconstructed models of the petrosal of Anancus arvernensis NMNHS.FM2991A in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.F. aquaeductus Fallopii, a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, e.w. epitympanic wing, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, m.p.c. mastoid pneumatic cell (broken), p.f. perilymphatic foramen, p.m. pars mastoidea (broken), pr promontorium, prot protuberance, t.t. tegmen tympani

Figure III. 22 :

 22 Figure III.22 : 3D reconstructed models and drawings of the petrosal of Anancus arvernensis NMNHS.FM2991D in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.F. aquaeductus Fallopii, a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, co cochlea, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, m.p.c. mastoid pneumatic cell (broken), p.f. perilymphatic foramen, p.m. pars mastoidea (broken), pr promontorium (broken), prot protuberance, s.c. stylomastoid canal, t.t. tegmen tympani

Figure III. 26 :

 26 Figure III.26 : 3D reconstructed models of the bony labyrinths of Anancus arvernensis specimens NMNHS.FM2991A (A), NMNHS.FM2991B (B), NMNHS.FM2991C (C), NMNHS.FM2991D (D), NMNHS.FM2991E (E), NMNHS.FM2991F (F) and NMNHS.FM2991G (G) in frontal view. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea, f.v. fenestra vestibuli, he helicotrema, l.a. lateral ampulla, l.c. lateral semicircular canal, p.a. posterior ampulla, p.c. posterior semicircular canal, p.f. perilymphatic foramen.

Figure III. 27 :

 27 Figure III.27 : 3D reconstructed models of the bony labyrinths of Anancus arvernensis specimens NMNHS.FM2991A (A), NMNHS.FM2991B (B), NMNHS.FM2991C (C), NMNHS.FM2991D (D), NMNHS.FM2991E (E), NMNHS.FM2991F (F) and NMNHS.FM2991G (G) in anterior canal view. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea.

Figure III. 28 :

 28 Figure III.28 : 3D reconstructed models of the bony labyrinths of Anancus arvernensis specimens NMNHS.FM2991A (A), NMNHS.FM2991B (B), NMNHS.FM2991C (C), NMNHS.FM2991D (D), NMNHS.FM2991E (E), NMNHS.FM2991F (F) and NMNHS.FM2991G (G) in posterior canal view. Legends: a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea, p.a. posterior ampulla, p.c. posterior semicircular canal, p.f. perilymphatic foramen.

Figure III. 29 :

 29 Figure III.29 : 3D reconstructed models of the bony labyrinths of Anancus arvernensis specimens NMNHS.FM2991A (A), NMNHS.FM2991B (B), NMNHS.FM2991C (C), NMNHS.FM2991D (D), NMNHS.FM2991E (E), NMNHS.FM2991F (F) and NMNHS.FM2991G (G) in lateral canal view. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, c.c. crus commune, co cochlea, l.a. lateral ampulla, l.c. lateral semicircular canal, p.a. posterior ampulla, p.c. posterior semicircular canal.

Figure III. 30 :

 30 Figure III.30 : 3D reconstructed models of the bony labyrinths of Anancus arvernensis specimens NMNHS.FM2991A (A), NMNHS.FM2991C (B), NMNHS.FM2991D (C), NMNHS.FM2991E (D), NMNHS.FM2991F (E) and NMNHS.FM2991G (F) in cochlear view. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, co cochlea, f.v. fenestra vestibuli, he helicotrema, l.a. lateral ampulla, l.c. lateral semicircular canal, mo modiolus, p.c. posterior semicircular canal, p.f. perilymphatic foramen.

(

  , they are a little more circular while the flattening is more pronounced in NMNHS.FM2991B and at the level of the anterior canal of NMNHS.FM2991E. The slender part of the lateral semicircular canal is connected to the vestibule at a high position and clearly distant from the posterior ampulla. NMNHS.FM2991A and NMNHS.FM2991D display no ridges on their canals. NMNHS.FM2991C and NMNHS.FM2991E have a ridge on their anterior and posterior canals while NMNHS.FM2991F and NMNHS.FM2991G have a ridge only on their posterior and anterior canal respectively. In NMNHS.FM2991B, all three canals have a ridge along the inner trajectory of each canal. The lateral canal displays a second ridge which is quite small and gives the impression that a small part of the canal has been folded. It is located on the trough of the ventral part of the canal. No other specimen displays this type of ridge. Every canal of every specimen displays at least a small undulation except for the lateral canal of NMNHS.FM2991G. The undulation is particularly well marked on the lateral canals of NMNHS.FM2991E and NMNHS.FM2991F and on the anterior canal of NMNHS.FM2991C.

of 31 )

 31 Anancus is no doubt that this specimen displays at least two and a half turns. Only three specimens have a fully preserved cochlea (NMNHS.FM2991A, NMNHS.FM2991D, NMNHS.FM2991E).The precise length of the cochlea of these specimens is given in TableIII.1. While the cochleae of NMNHS.FM2991D and NMNHS.FM2991E have almost the same length (around 79 mm), the cochlea of NMNHS.FM2991A is slightly shorter (around 72 mm). In ventral view, the III -Anatomy of the ear region of fossil proboscideans modiolus of all specimens is completely overlapped by the apical turn and there is no visible gap. The basal turn of the cochlea is only partially overlapped by the apical turn and is still visible in ventral view. The lamina secundaria is absent in all specimens. 3.2.10. Stegodon orientalis Only one specimen of the genus Stegodon was CT-scanned (FM18632) and it consists of a juvenile skull bearing both the right and left petrosals. Even though the specimen is mineralized, both inner ears were segmented. The total volume of a Stegodon inner ear is 1117 mm 3 . Petrosal (Fig III.The petrosals of Stegodon are more or less complete and still attached to the skull. Due to the large size of the specimen, the voxel size is great (141.85 µm) and the resolution is therefore low. This and the advanced mineralization of the specimen contribute to the poor contrast of the microtomographic sections, making the distinction between the petrosal and the tympanic very difficult. Hence, the pars mastoidea and the tegmen tympani were not fully segmented at the level of their connection with the tympanic. In general, the petrosal of Stegodon is similar to the petrosal of extant elephants. In cerebellar view, the aquaeductus vestibuli is oriented in the same way but it is smaller. Antero-laterally to the aquaeductus vestibuli, the cerebellar surface is very bulbous. The surface located antero-laterally to that bulbous structure is slightly concave and could be a shallow subarcuate fossa. The crista partis petrosa is blunt. The internal auditory meatus is filled with sediments and was difficult to segment but its opening on the cerebellar surface is distinct. It is oriented antero-posteriorly as in the other elephantimorphs. The epitympanic wing is preserved and very thin. The angle between the cerebral and cerebellar surfaces of the petrosal is more acute than in extant elephants (85°). In cerebral view, the tegmen tympani is not fully segmented but the groove for the middle meningeal artery is visible. It is narrower and shallower than in extant elephants. In tympanic view, the promontorium is completely preserved and very prominent. It does not display the "two-parts" morphology seen in some extant elephants. The poor contrast prevents from segmenting the aquaeductus Fallopii. The crista interfenestralis is preserved and thick. I was not able to segment the pars

Figure III. 31 :Figure III. 32 :

 3132 Figure III.31 : 3D reconstructed models and drawings of the right petrosal of Stegodon orientalis FM18632 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, co cochlea, f.v. fenestra vestibuli, i.a.m. internal auditory meatus, p.f. perilymphatic foramen, p.m. pars mastoidea (broken), pr promontorium, t.t. tegmen tympani (partially reconstructed)

32 )

 32 mm. The average section radius for the lateral canal is slightly lower (0.77 mm) than the other canals as well. The thickness ratio of this canal (5.1) is clearly higher than that for the anterior and posterior canals, even though it is not noticeable on the reconstruction. The radius of curvature of the lateral canal is 3.27. The angle between the anterior and posterior canals and the angle between the posterior and lateral canals are particularly large (respectively 107.6° and 94°). In contrast, the angle between the anterior and lateral canals is clearly lower (74.9°). The lateral canal is clearly smaller (radius of 3.27) than the anterior and posterior canals. The smaller size of the lateral canal is extremely marked and visible on the reconstruction. The posterior canal is the largest one with a radius of curvature of 7.48 (radius of curvature of the anterior canal: 5.36). The anterior canal apex is located slightly higher than the posterior one in both ears. In Stegodon, the degree of thickness of the semicircular canals is high compared to other proboscideans and mammals (average thickness ratio = 4.04). The canals are flattened in cross-section and the slender part of the lateral canal enters the vestibule at a quite high position, distant to the posterior ampulla. Hence there is no fusion between the lateral and posterior canals. There is a ridge on the anterior and posterior canals of both ears, the anterior ridge being particularly sharp. All the canals display an undulation but the anterior canal is clearly more undulated than the others. Cochlear bony labyrinth (Fig III.The cochlear part is fully preserved in both ears of the studied specimen of Stegodon orientalis (FM18632). The cochlea displays 2 turns (720°) and a length of 68.7 mm. In ventral view, the modiolus is slightly loose and we can see a gap there. The basal turn of the cochlea is only partially overlapped by the apical turn and is still visible in ventral view. The lamina secundaria is absent. The cochlear volume (508 mm 3 ) represents around 45% of the total volume of the bony labyrinth.

  species of Mammuthus have been studied. First, the right isolated petrosal bone of Mammuthus primigenius (MNHN.F.1904-12) has been scanned and segmented. This specimen displays a complete inner ear even though the cochlear part is a little damaged. The total volume of the Mammuthus primigenius inner ear is around 1131 mm 3 . Secondly, two isolated petrosals (left and right) of the same specimen of a Mammuthus columbi (FM 144658) have been scanned and segmented. However, the cochlear part is broken on both petrosals; hence the total volume of the inner ear is unknown for this species. Petrosal (Fig III.33-34) The overall aspect of the petrosal is very similar as the petrosal of extant elephants. In cerebellar view, the subarcuate fossa is absent. While the area surrounding the aquaeductus vestibuli is slightly convex in Mammuthus columbi, it is concave is Mammuthus primigenius. In both species, the aquaeductus vestibuli has the shape of an elongated slit located in the posteromedial corner of the petrosal. In Mammuthus primigenius, the slit is somewhat covered by the cerebellar surface of the petrosal. The crista partis III -Anatomy of the ear region of fossil proboscideans petrosa is blunt in every specimen of Mammuthus. The angle between the cerebral and the cerebellar surfaces of the petrosal is obtuse in both species, but it is larger in M. primigenius (112°) than in M. columbi (101° for the right ear, 103° for the left ear). While the internal auditory meatus is completely broken in Mammuthus columbi, it is better preserved in Mammuthus primigenius. It is oriented antero-posteriorly as in extant elephants. In cerebral view, the tegmen tympani is pretty shattered in M. columbi. The groove for the middle meningeal artery is not visible in both left and right ears but a thin groove runs across the cerebral surface parallel to the crista partis petrosa. In M. primigenius, the tegmen tympani is better preserved. The groove for the middle meningeal artery is visible and located on the ventral part of the surface which is connected in life with the squamosal bone. The groove is thinner and shallower than in extant elephants. In tympanic view, the petrosal of M. primigenius is better preserved than the petrosal of M. columbi. In the latter, the promontorium is damaged in both ears preventing any observation of the fenestra vestibuli and the perilymphatic foramen. These structures are preserved in M. primigenius. The promontorium is bulbous and displays a secondary bulging structure as in every Elephas and some Loxodonta specimen. The fenestra vestibuli is damaged, but it appears oval. The perilymphatic foramen is preserved and similar to the foramen of extant elephants. The crista interfenestralis is thick but the tympanohyal is not preserved hence the condition of the stapedial foramen remains unknown. The pars mastoidea is almost completely damaged in both species. Only the imprints of the tympanic cavities contained in the pars mastoidea are visible (particularly in the right ear of M. columbi). The roof of the aquaeductus Fallopii is partially broken in both ears of M. columbi, giving it the aspect of a groove. However, it seems to display the posteriorly opened condition seen in extant elephants. In M. primigenius, the roof is preserved and covers the whole canal except for its region close to the crista interfenestralis (posteriorly opened condition). On the flange of bone forming the roof of the canal, the fossa incudis is clearly visible in M. primigenius. A similar fossa is visible in the right ear of M. columbi but it is shallower and less marked.

Figure III. 33 :

 33 Figure III.33 : 3D reconstructed models of the right petrosal of Mammuthus primigenius MNHN.F.1904-12 in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, f.v. fenestra vestibuli, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus (broken), p.f. perilymphatic foramen, pr promontorium (broken), s.c. stylomastoid canal, t.t. tegmen tympani

  Mammuthus columbi but displays a horizontal bulge in the extension of the posterior semicircular canal ridge. The average section radius of the crus commune of Mammuthus columbi is 1.41 mm (right: 1.38 mm, left: 1.43 mm). It is slightly larger in Mammuthus primigenius (1.42 mm). The average length of the crus commune is 5.24 mm in Mammuthus columbi (right: 5.64 mm, left: 4.83 mm) and it is also higher in Mammuthus primigenius (5.57 mm). M. columbi displays a stockier crus commune with a thickness ratio of 27.04 (right: 24.52, left: 29.57) compared to M. primigenius (thickness ratio of 25.45). In both specimens, the anterior and posterior semicircular canals meet quite low, approximately at the mid-height of the anterior canal. The crus commune is not tilted in any specimen. Semicircular canals The anterior semicircular canal is oval in both studied species of Mammuthus. The major axis of the canal forms an angle of 42° with the crus commune in both ears of the Mammuthus columbi specimen while the angle is higher in the Mammuthus primigenius specimen (52°). The anterior semicircular canal appears slightly more slender in Mammuthus primigenius than in Mammuthus columbi. This is supported by the thickness ratio values of the specimens. The central streamline of the anterior canal is very similar in Mammuthus columbi (25.95 mm) and Mammuthus primigenius (26.22 mm). The average section radius of the anterior canal is however slightly higher in Mammuthus columbi (1.10 mm) than in Mammuthus primigenius (0.88 mm). Therefore, the thickness ratio of this canal is 4.24 in M. columbi and 3.28 in M. primigenius. The radii of curvature of the anterior canal are very similar in both species (5.71 in M. columbi and 5.80 in M. primigenius).

Figure III. 35 :

 35 Figure III.35 : 3D reconstructed models of the bony labyrinths of Mammuthus primigenius MNHN.F.1904-12 (A-E) and Mammuthus columbi FM144658, right (F-I) and left (J-M, mirrored) in frontal (A,F,J), anterior canal (B,G,K), posterior canal (C,H,L), lateral canal (D,I,M) and cochlear (E) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.v. aquaeductus vestibuli, c.c. crus commune, co cochlea, f.v. fenestra vestibuli, l.a. lateral ampulla, l.c. lateral semicircular canal, p.a. posterior ampulla, p.c. posterior semicircular canal, p.f. perilymphatic foramen.

Figure III. 36 :

 36 Figure III.36 : 3D reconstructed models of the left bony labyrinth of Palaeoloxodon antiquus M82706 (mirrored) in frontal (A), anterior canal (B), posterior canal (C) and lateral canal (D) views. Legends: a.a. anterior ampulla, a.c. anterior semicircular canal, a.c.r. anterior canal ridge, a.v. aquaeductus vestibuli, c.c. crus commune, c.c.r. crus commune ridge, i.a.v. insertion of the aquaeductus vestibuli, l.a. lateral ampulla, l.c. lateral semicircular canal, p.a. posterior ampulla, p.c. posterior semicircular canal, p.c.r. posterior canal ridge.

Figure 37 :

 37 Figure 37 : 3D reconstructed models of the left petrosal of Palaeoloxodon antiquus M82706 (mirrored) in medial (A), tympanic (B), cerebellar (C) and cerebral (D) views. Legends: a.F. aquaeductus Fallopii, a.v. aquaeductus vestibuli, c.p.p. crista partis petrosa, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus (broken), p.m. pars mastoidea (broken), pr promontorium (broken), s.c. stylomastoid canal, t.t. tegmen tympani (broken)

in

  internal auditory meatus is a structure that houses the foramen acusticum superius (cranial nerve VII) and the foramen acusticum inferius (cranial nerve VIII). While the meatus is oriented dorsomedially in other mammals, Prodeinotherium bavaricum but given the morphology of the petrosal, the meatus was certainly oriented anteroposteriorly as in modern proboscideans. 209 III -Anatomy of the ear region of fossil proboscideans Tegmen tympani In Ocepeia daouiensis (Gheerbrant et al. 2014) and Eritherium azzouzorum (chapter I, Schmitt & Gheerbrant, 2016), the tegmen tympani exhibits a very similar structure. It is more or less kidney-shaped and highly inflated. The anterior part of the tegmen tympani is perforated by a large bony canal that most probably corresponds to the passage of the ramus superior for the stapedial artery. Among the outgroups, the tegmen tympani is not developed (if present) in the , 2016). The tegmen tympani of Numidotherium koholense displays a different structure (Benoit et al. 2013b). It is quite inflated (but less than in Eritherium and Ocepeia) but it forms a flat surface dorsally (cerebral surface). The petrosal of Prodeinotherium bavaricum is similar. It is inflated, and more than in Numidotherium, but it forms a very large and flat cerebral surface; this results in a dorsal petrosal aspect similar to those of modern elephants, with two large surfaces, the cerebellar and cerebral surfaces. In Mammut americanum, the tegmen tympani is large, flat and not inflated, as in modern elephants. On its dorsal surface runs a deep groove for the middle meningeal artery. This tegmen tympani morphology is observed in all other studied elephantimorphs.

Fig

  Fig. III.38). Indeed, the values form a continuum which is more or less contained within the variation range observed in the Friesenhahn elephantimorphs. Therefore, we decided to exclude this character from the phylogenetic analysis.

Figure III. 38 :

 38 Figure III.38 : Distribution of the stapedial ratio values within proboscideans and some outgroups. Values are summarized in Appendix 11.

  is the usually inflated transition region that connects the slender part with the vestibule. In life, this is where the ampulla of the semicircular duct is located. This membranous structure holds many crucial structures for the detection of the angular accelerations such as the crista and the cupula. The bony ampulla consists of a bulging structure connected to the vestibule and to the slender part of the semicircular canal. The anterior and lateral ampullae are located close to each other while the posterior ampulla is generally close to point of entry of the slender part of the lateral canal into the vestibule. The definition of the ampullae (their identification from the slender part of the canal and the vestibule) is however variable. In embrithopods (Arsinoitherium and Embrithopoda PM53) the ampullae are well defined and bulbous. This is generally the case in all non-proboscidean placental taxa that we used for comparisons; Ocepeia (Gheerbrant et al. 2014), Seggeurius (Benoit et al. 2015), Procavia, Prorastomus and the sirenian from Chambi (Benoit et al. 2013a) and Elephantulus. In the earliest-known proboscideans (Eritherium, Phosphatherium and Numidotherium), the ampullae are well-defined as well. In contrast, the ampullae appear poorly defined in all the other studied proboscideans. The less defined bony ampullae house less defined membranous ampullae in Elephas CEB150009 (see chapter II). This suggests that the membranous ampullae of most proboscideans also display this condition.

  variable. It can be high (at the three quarters of the height of the anterior canal) or quite low (at about the midheight of the anterior canal

Figure III. 39 :

 39 Figure III.39 : Distribution of the crus commune thickness ratio within proboscideans and some outgroups. Values are summarized in Appendix 12.

  anterior canal is quite round. It is oval in all other proboscideans, with the exception of one of the Gomphotherium specimens (CBar coll. V2). Regarding non-proboscidean taxa, the canal is very round in both studied embrithopods (Arsinoitherium and Embrithopoda PM53) and in both ears of the early afrotherian Ocepeia. It appears round as well in both Prorastomus and the sirenian from Chambi (Benoit et al. 2013a)

  characters. Larger mammals tend to display larger radii. Hence, it is not pertinent to discuss the radii separately among proboscideans. However, the discussion of the relative sizes of the III -Anatomy of the ear region of fossil proboscideans canals seems to be relevant. Comparison of the radii of curvature shows that the vertical canals (the anterior and posterior canals) always display similar values while the lateral canal is smaller. However, the relative size of the lateral canal compared to the other two is variable. We established a ratio to compare the relative size of the lateral canals among our specimens and other mammals: r = lateral radius/[(anterior radius + posterior radius)/2]*100. It gives the relative size of the lateral canal in percentage compared to the mean of the vertical canals radii. The distribution of this ratio is given in Fig. III.40. Given the distribution, we decided to separate specimens in three groups with three distinct states: those with a lateral canal approximately as large or larger than the vertical canals (ratio over 83%), those with an average size of the lateral canal (ratio between 72% and 83%) and those with relatively small lateral canals (ratio under 72%). The character is constant intra-specifically, except for Elephas maximus which shows specimens with average and small canals. Early proboscideans such as Eritherium, Phosphatherium, Numidotherium and Prodeinotherium display average lateral canals. All studied later proboscideans display relatively small lateral canals, with the exceptions of Palaeoloxodon and some Elephas maximus specimens (CEB150009 and MNHN.F.2008-81) that display average canals.

Figure III. 40 :

 40 Figure III.40 : Distribution of the ratio measuring the relative size of the lateral canals compared to the mean of the vertical canals in percentage (based on radii of curvature values). Values are summarized in Appendix 13.

Figure III. 41 :

 41 Figure III.41 : Distribution of the angles between the anterior and posterior (A), anterior and lateral (B) and posterior and lateral (C) semicircular canals among our sample. Values are summarized in Appendix 14.

  Ocepeia and sirenians(Benoit et al. 2013a). However, all the other later proboscideans studied here display flattened semicircular canals. In addition, the same morphology was described byBenoit et al. (2013b) in the anterior and posterior canals of the embrithopod Arsinoitherium. However, the earlier Moroccan embrithopod PM53 does not display flattened canals.

  ratio. As explained in the Material and Methods section, this ratio is the mean of the thickness ratio of each semicircular canal. The individual value is calculated in as following: average section radius / III -Anatomy of the ear region of fossil proboscideans semicircular canal length * 100. The values of the global thickness ratio are given in

  intraspecific variability. It is strictly constant in specimens belonging to the same genus or species. In the early afrotherian Ocepeia, it enters the vestibule at a quite high position and close to the posterior ampulla. This condition is found in the early sirenians Prorastomus and the sirenian from Chambi as well. PAL.2013.01108E), the lateral canal enters the vestibule at a high position as well, but the point of entry is distant from the posterior ampulla. In all the specimens of Loxodonta, Elephas, Mammuthus and Palaeoloxodon, the lateral canal enters the vestibule quite low. Given its regularity among specimens of the same species and its easily defined states, this character is interesting for a phylogenetic analysis. Fusion of the lateral and posterior canals When close to each other, the lateral and posterior bony semicircular canals can be fully or partially fused. The total fusion is often called crus commune 222 III -Anatomy of the ear region of fossil proboscideans secundaria or secondary common crus in the literature. We find the term to be confusing because this structure differs from the "primary" crus commune (between the anterior and posterior canals). While the membranous ducts of the anterior and posterior canals are fused within the crus commune, the membranous ducts of the posterior and lateral canals are never fused at the level of the crus commune secundaria[START_REF] Gray | The Labyrinth of Animals[END_REF][START_REF] Gray | The Labyrinth of Animals[END_REF][START_REF] David | Le système des canaux semi-circulaires des archosaures : anatomie, morphométrie, morphologie fonctionnelle, évolution[END_REF]. The first crus commune observed in the bony labyrinth is linked to a functional feature which is the presence of the membranous crus commune between the anterior and posterior membranous ducts. However, the crus commune secundaria is merely an ossification artefact linked to the location of the lateral canal relative to the posterior canal. In early proboscideans such as Eritherium, Phosphatherium and Numidotherium, both the ampulla and the slender part of the posterior canal are in contact with the lateral canal. In Eritherium, only a small part of the posterior bony slender canal is fused with the lateral while large parts of the slender canals are fused in Phosphatherium and Numidotherium forming what is usually called the crus commune secundaria. The morphology observed in Eritherium can also be found in some specimens of Elephas (MNHN.AC.ZM.1904AC.ZM.1961-69 for instance). The lateral canal is completely independent from the posterior canal in Anancus, least two full turns. The notable exceptions are Numidotherium (1.5 or 1.62 depending on the specimen) and the right ear of Loxodonta specimen MNHN.ZM.AC.2008-71 which displays 1.625 turns. However, as mentioned in chapter II, the number of turns is extremely variable intra-specifically. The difference can be up to one full turn between two different specimens of Loxodonta (from 1.625 turns to 2.625). The number of turns of the cochlea can vary even within the same specimen: MNHN.ZM.AC.2008-71 displays a left ear with two turns while its right ear displays 1.625 turns. Such as intraspecific variation seems to weaken the pertinence of this character for a phylogenetic analysis. The distribution of the number of turns of the cochlea among our taxa sample and other afrotherians (see Fig III.43) is indeed irrelevant to discriminate groups in this range. However, there is a clear separation between specimens with a very high level of coiling (more than 3.3 turns) and those with a lower level of coiling (less than 2.63 turns). This separation would allow us to maintain this character in our phylogenetic analysis while taking into account the intraspecific variability. Relative volume of the cochlea The relative volume of the cochlea has to been taken with caution because it depends on the protocol used to separate the cochlear canal from the vestibular part of the bony labyrinth. We used the protocol detailed in the main 'Material & Method' section of the thesis. However, according to the specimen, the separation of the cochlear part can be slightly different. Hence the given values for the relative cochlear volume are estimations.On the other hand, some values that we use for comparisons come from different authors which separation protocols might be different. In summary, it is possible to compare the relative volumes but only at a certain level of precision. Nevertheless, this value is not accessible for several specimens as many fossil proboscideans that we sampled do not preserve the cochlea.

Figure III. 43 :

 43 Figure III.43 : Distribution of the number of turns of the cochlea within proboscideans and some outgroups. Values are summarized in Appendix 16.

  used in the literature. Therefore, our ratios are fully comparable with ratios obtained from different authors. The distribution of the ratios among our taxa sample and some outgroups (Fig.III.45) shows roughly two groups: those with a ratio inferior to 0.6 and those with a ratio superior to 0.6. Hence, the coding proposed inBenoit et al. (2013b) is pertinent and we will use this character with the same states in our phylogenetic analysis (chapter V). A cochlea with a high aspect ratio seems to be plesiomorphic among afrotherians. Ocepeia has a rather 225 III -Anatomy of the ear region of fossil proboscideans high aspect ratio (0.72). However, the aspect ratio is low (always inferior to 0.6) in all studied proboscideans preserving the cochlea fully.

Figure III. 44 :

 44 Figure III.44: Distribution of the relative volume of the cochlea within proboscideans (in %). Values are summarized in Appendix 17.

Loxodonta

  as only one specimen displays one (CEB130168). A small apical lacuna is also seen in both ears of Stegodon, two Numidotherium specimens (UOK5 and the unlabeled specimens described inBenoit et al. (2013b) but not in the specimen described in[START_REF] Court | Cochlea anatomy of Numidotherium koholense : auditory acuity in the oldest known proboscidean[END_REF]

  secundaria) is a structure that excavates the external part of the cochlear canal. It marks the separation between the scala tympani and the scala vestibuli. It is present in the cochlea of most mammals, but it is absent in most of the proboscidean studied here. In fact, among proboscideans, only the early representatives such as Eritherium, Phosphatherium and Numidotherium display a secondary bony lamina. In Phosphatherium, it is extremely shallow and in Numidotherium, it has only been observed in the specimen described in Court, 1992. Its absence in UOK5 and in the unlabeled specimen segmented in Benoit et al. (2013b) can either be III -Anatomy of the ear region of fossil proboscideans explained by the poor resolution of the microtomographic slices in both studies or by an intraspecific variability of this character. The other proboscideans lack a lamina secundaria.

Figure III. 45 :

 45 Figure III.45: Distribution of the cochlear aspect ratio within proboscideans and some outgroups. Values are summarized in Appendix 18.

  Benoit et al. (2013b).The angle between the crus commune and the plane defined by the first turn of the cochlea is measured. The distribution of this angle among our taxa sample and some outgroups (Fig. III.46) shows a gap between specimens with an acute or right angle (Elephantulus, Tenrec) and the other specimens. On the other hand, a smaller gap is visible between 140° and 144°, which allows defining a second (angle comprised between 90° and 142°) and third group (angle superior to 142°). This definition allows minimizing the polymorphism when this feature is used as a phylogenetic character. All specimens of Anancus and Elephas display an angle superior to 146° (see Appendix 19).

Figure III. 46 :

 46 Figure III.46 : Distribution of the vestibulocochlear angle within proboscideans and some outgroups. Values are summarized in Appendix 19.

  observations confirm the presence of intra-specific variability of certain characters of the petrosal and the inner, already described in extant elephants in Chapter II. Almost the entire interspecific variation of the stapedial ratio of proboscideans is contained within the variation range of Elephas. The inclination of the crus commune varies within Anancus arvernensis. The shape of the lateral canal is also variable intraspecifically. The number of turns varies greatly in Loxodonta and the presence of an apical lacuna seems variable intraspecifically as well. In order to minimize polymorphisms within our data, we decided not to include such characters in the phylogenetic analysis performed in Chapter V. Conversely, comparisons of the petrosal and inner ear of extinct and extant proboscideans and afrotherians confirm the importance of some characters. The subarcuate fossa depth seems rather constant intra-specifically but varies greatly within proboscideans and afrotherians. The tegmen tympani displays a characteristic shape in some taxa. The study of the perilymphatic foramen remains of great interest. Among others, the flattening of the canals, the relative volume and aspect ratio of the cochlea, the presence (or absence) of the lamina secundaria and the vestibulocochlear angle appear to be quite constant intra-specifically, but they vary within ampullae, the basal thickening of the crus commune, the apical extension of the anterior canal or the position of the lateral canal insertion into the vestibule with respect to the posterior ampulla. Some features are also reappraised using quantitative ratios: crus commune thickness ratio, relative size of the lateral canal and semicircular canal thickness ratio. These characters are to be included in a cladistic analysis to test the phylogenetic message that they carry.

  time to include the extant members of Sirenia (only two fossil specimens are included in our sample).

  raw 3D models of bony labyrinths were exported as it is, without smoothing or reduction. The specimens were then prepared in GEOMAGICS Studio 2012 following the same protocol for each 3D model (decimation, smoothing, spikes removal and repair). This allows minimizing the effect of differential smoothing that could introduce a bias in the analysis. Landmarks were then placed using AVIZO with the protocol described in the introduction of the thesis. This protocol was originally used in order to conduct functional inferences with the software ARIADNE (chapter VI) and it does not require having landmark sets that contain the same number of landmarks (for example, the cochlear set of landmarks can contain 48 landmarks in one specimen and 51 in another one).

  -Geometric morphometrics study of the bony labyrinths of proboscideans and afrotherians Procrustes superimposition is then performed on the landmarks set and we used principal component analysis (PCA) on Procrustes coordinates to analyze the shape variability of the bony labyrinth. Deformations of the bony labyrinth among the PC axes were visualized with MORPHOTOOLS. The PC scores were exported and we used the software R (R Development Core Team, 2008) to visualize the distribution of specimens within the morphospace. Regressions While the analyses presented in this chapter were performed on the bony labyrinth shape, which is supposedly free of size, size can still influence the results we get via allometry. To investigate allometry, phylogenetic generalized least squared regressions were performed between the three first PC scores of the first four analyses (A1, A2, P1 and P2) and the logarithm of body mass. To do so, we used estimates of the body mass found in the literature as well as a hypothetic phylogenetic tree representing the relationships between the taxa used in the geometric morphometrics analysis. Details are given in Appendix 20 and 21.Phylogenetic regressions were used to account for the non-independency of the data, arising from the shared evolutionary history of the species. The topology of this tree, as well as the divergence dates mainly come fromTassy (pers. comm. 2016). Regressions were not performed for analyses E1 and E2 (extant elephants), because of the lack of species.

Afrotheria 3 . 1 . 1 .

 311 Analysis A1 of the whole labyrinth The results of the PCA performed on the whole labyrinth are given in Fig IV.4. The first three axes of the PCA explain 67.8% (PC1: 31.8%, PC2: 23.5%, PC3: 12.5%) of the total variation of the labyrinth morphology. Deformations PC1 (31.8%) The deformations of the bony labyrinth along the first axis (PC1 which explains 31.8% of the total variation) are given in Fig IV.1 in several views. Towards negative values, the angle between the cochlea and the lateral canal tends to be more acute (Fig IV.1A). The cochlea is smaller with less turns. The anterior canal tends to be rounder. The lateral canal tends to be larger and rounder. It expands towards the posterior canal and the utricular end of the slender lateral canal is located higher with respect to the posterior ampulla. The angle between the anterior and posterior canals and the angle between the posterior and lateral canals tend to be more obtuse. Towards positive values, the angle between the cochlea and the lateral canal is a little more obtuse. The cochlea tends to be larger, with a second turn more developed. The anterior canal tends to be more oval while the lateral canal tends to be smaller and more oval. The angle between the anterior and posterior canals and the angle between the posterior and lateral canals tend to be more acute. PC2 (23.5%) The deformations of the bony labyrinth along the second axis (PC2 which explains 23.5% of the total variation) are given in Fig IV.2 in several views. Towards the negative values, the three semicircular canals show a more oval shape. The angle between the anterior and posterior canals tends to be more acute. The cochlea displays less turns and is more tightly coiled. Conversely, the three semicircular canals tend to display a rounder shape towards positive values. The angle between the anterior and posterior canals is more obtuse and the cochlea displays a larger number of turns and is less tightly coiled.

Figure IV. 1 :

 1 Figure IV.1 : Deformations along the first axis of the analysis (PC1, 31.8%) conducted on the whole labyrinth of Afrotheria (A1) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals and the cochlea (D). "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 2 :

 2 Figure IV.2 : Deformations along the second axis of the analysis (PC2, 23.5%) conducted on the whole labyrinth of Afrotheria (A1) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals and the cochlea (D). "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 3 :

 3 Figure IV.3 :Deformations along the third axis of the analysis (PC3, 12.5%) conducted on the whole labyrinth of Afrotheria (A1) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals and the cochlea (D). "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

  is a difficult feature to analyze through geometric morphometrics (pers. comm.Philipp Gunz 2016). Numidotherium andProrastomus plot close to each other. This is not a surprise given the similarities seen in both specimens such as a loose cochlea that displays 1.5 turns. Other afrotherians (Eritherium, the sirenian from Chambi, Ocepeia, Tenrec and Elephantulus) plot more or less together.

Figure IV. 4 :

 4 Figure IV.4 : Shape differentiation of the whole bony labyrinth of afrotherians (analysis A1). A) 3D Morphospace in the view best illustrating the two clusters. B) Principal components 1 and 2 and C) principal components 1 and 3. Green cluster: non-proboscideans. Grey cluster: proboscideans.

Figure IV. 5 :

 5 Figure IV.5 : Deformations along the first axis of the analysis (PC1, 40.6%) restricted to the semicircular canals of Afrotheria (A2) in the view showing the plane of the anterior (A), posterior (B)and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 6 :

 6 Figure IV.6 : Deformations along the second axis of the analysis (PC2, 15.5%) restricted to the semicircular canals of Afrotheria (A2) in the view showing the plane of the anterior (A), posterior (B)and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 7 :

 7 Figure IV.7 : Deformations along the third axis of the analysis (PC3, 8.5%) restricted to the semicircular canals of Afrotheria (A2) in the view showing the plane of the anterior (A), posterior (B)and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 8 :

 8 Figure IV.8 : Shape differentiation of the semicircular canals of afrotherians (analysis A2). A) 3D Morphospace in the view best illustrating the three clusters. B) Principal components 1 and 2 and C) principal components 1 and 3. Green cluster: non-proboscideans. Grey cluster: proboscideans. Red cluster: Elephantimorpha + Prodeinotherium.

  The deformations of the bony labyrinth along the first axis (PC1 which explains 36.6% of the total variation) are given in Fig IV.9 in several views. This axis seems to be controlled by the cochlear morphology only. The cochlea is more tightly coiled towards the negative values while it is less coiled towards the positive values. On the other hand, the number of turns appears to decrease towards the negative values. The angle between the cochlea and the lateral canal decreases towards the negative values and it increases towards the positive values. PC2 (19.8%) The deformations of the bony labyrinth along the second axis (PC2 which explains 19.8% of the total variation) are given in Fig IV.10 in several views. The cochlea is less coiled towards negative values while it is more tightly coiled towards positive values. The axis of rotation of the apical turn is displaced with respect to the axis of rotation of the basal turn towards positive values. The anterior canal is rounder towards negative values and the semicircular canals are more slender. The lateral canal also tends to increase and to expand toward the posterior canal. The posterior canal displays an apical expansion towards negative values as well. The crus commune shape is also affected along this axis. It is more elongated towards the negative extremity of the axis while it is shorter and stockier towards its positive extremity. Finally, the angle between the anterior and posterior canals increases towards negative values.

Figure IV. 9 :

 9 Figure IV.9 : Deformations along the first axis of the analysis (PC1, 36.6%) restricted to Proboscidea (P1) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals and the cochlea (D). "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 10 :

 10 Figure IV.10 : Deformations along the second axis of the analysis (PC2, 19.8%) restricted to Proboscidea (P1) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals and the cochlea (D). "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

  deformations of the bony labyrinth along the third axis (PC3 which explains 11% of the total variation) are given in Fig IV.11 in several views. The third PC is explained by a combination of both the canals and the cochlear features. First, the anterior canal is rounder towards positive values along this axis. The angle formed by the major axis of the oval posterior canal and the crus commune changes along this axis as well. It is more acute towards negative values and more obtuse towards positive values. The zone of insertion of the lateral canal into the vestibule is closer to the posterior ampulla towards the negative extremity of the axis while the opposite is observed towards the positive extremity of PC3. Finally, the cochlea is more tightly coiled towards negative values and looser towards positive values. based on cochlear and canals landmarks (Fig IV.12). This is mostly explained by the location of CEB130168 and MNHN.AC.ZM.2008-71 within the morphospace. MNHN.AC.ZM.2008-71 is located towards the negative values of PC1. Indeed, as observed in Chapter III, this specimen displays a particularly low number of turns (1.5) which is a feature controlled by PC1. This explains its location and its proximity along this axis to Numidotherium, which displays a cochlea with 1.5 turns as well. However, Numidotherium and MNHN.AC.ZM.2008-71 are very distant from each other along PC2. CEB130168 and Platybelodon are also close within the morphospace (especially along PC1) likely based on their shared number of turns of the cochlea (2 turns). Eritherium is located roughly at the same level as Platybelodon and CEB130168 along PC1, however, it is very distant from those two along PC2. Anancus specimens are close within the morphospace but they are included within the Elephantidae cluster as well as Stegodon. Specimens with a large number of turns (Anancus, Loxodonta specimens MNHN.AC.ZM

Figure IV. 11 :

 11 Figure IV.11 :Deformations along the third axis of the analysis (PC3, 11%) restricted to Proboscidea (P1) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals and the cochlea (D). "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 12 :

 12 Figure IV.12 : Shape differentiation of the whole labyrinth of proboscideans (analysis P1). A) Principal components 1 and 2 and B) principal components 1 and 3. Grey cluster: Elephantimorpha. Red cluster: Elephantidae. Early proboscideans are not represented in a cluster since they are only two of them in this analysis.

Figure IV. 14 :

 14 Figure IV.14 :Deformations along the second axis of the analysis (PC2, 15.4%) restricted to the semicircular canals of Proboscidea (P2) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 15 :

 15 Figure IV.15 :Deformations along the third axis of the analysis (PC3, 9.9%) restricted to the semicircular canals of Proboscidea (P2) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 16 :

 16 Figure IV.16 : Shape differentiation of the semicircular canals of proboscideans (analysis P2). A) Principal components 1 and 2 and B) principal components 1 and 3. Grey cluster: Elephantimorpha. Green cluster: genus Anancus. Brown cluster: Elephantidae. Violet cluster: non-elephantimorphs. Early proboscideans are not represented in a cluster since they are only two of them in this analysis.

Figure IV. 17 :

 17 Figure IV.17 : Deformations along the first axis (PC1, 52.2%) of the analysis on the whole labyrinth of extant elephants (E1) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 18 :

 18 Figure IV.18 :Deformations along the second axis (PC2, 14.8%) of the analysis on the whole labyrinth of extant elephants (E1) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 19 :

 19 Figure IV.19 :Deformations along the third axis (PC3, 12%) of the analysis on the whole labyrinth of extant elephants (E1) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 20 :

 20 Figure IV.20 : Shape differentiation of the whole labyrinth of extant elephants (analysis E1). A) Principal components 1 and 2 and B) principal components 1 and 3. Blue cluster: Loxodonta. Red cluster: Elephas.

Figure IV. 21 :

 21 Figure IV.21 :Deformations along the first axis (PC1, 36.2%) of the analysis restricted to the semicircular canals of extant elephants (E2) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 22 :

 22 Figure IV.22 :Deformations along the second axis (PC2, 17.1%) of the analysis restricted to the semicircular canals of extant elephants (E2) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 23 :

 23 Figure IV.23 :Deformations along the third axis (PC3, 12.8%) of the analysis restricted to the semicircular canals of extant elephants (E2) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

Figure IV. 24 :

 24 Figure IV.24 : Shape differentiation of the semicircular canals of extant elephants (analysis E2). A) Principal components 1 and 2 and B) principal components 1 and 3. Blue cluster: Loxodonta. Red cluster: Elephas.

  clusters of the African and Asian elephants overlap. However, we can note that the first PC explains a larger part (52.2%) of the total variation in the analysis including IV -Geometric morphometrics study of the bony labyrinths of proboscideans and afrotherians the cochlea (E1). In fact, this axis in E1 is totally controlled by the cochlear morphology while the second and third axes are controlled by a combination of both cochlea and canals. The morphology of the cochlea has clearly a huge impact on the results. Indeed, the cochlea displays a great variability among extant elephants (Chapter II). The addition of the cochlea to the analysis results in a different repartition of the specimens within the morphospace. In E1, the most extreme taxa are Loxodonta MNHN.AC.ZM.2008-71 and CEB130168 which is easily explained by the particularly low number of turns of the cochlea they exhibit. On the other hand, the most extreme taxa are Loxodonta MNHN.AC.ZM.1861-53 and 1956-194 along PC1, and 1957-465 along PC2 in the E2 analysis. Clearly, the number of turns of the cochlea and its degree of coiling play a major role in the repartition of the specimens within the morphospace. Unfortunately, the intraspecific and even intra-individual variability of these features (see Chapter II) also adds noise and contribute to prevent the full discrimination of both genera.

  in the analysis restricted to semicircular canals (A2) than in the analysis that includes the cochlea (A1). The first PC in A2 (analysis restricted to semicircular canals) explains more of the total variation than the first PC in A1 (analysis on the whole labyrinth). The cochlea explains a great part of the variability along the first PCs of A1. Procavia exhibits an extreme morphology in both A1 and A2 but it is more marked in A2 (analysis restricted to the semicircular canals). This means that the semicircular canals of Procavia are very different, in addition to its cochlea (which displays 3.5 turns). Indeed, the zone of insertion of the lateral canal into the vestibule is very high and close to the crus commune and the lateral canal crosses the plane defined by the posterior canal. Those features are seen in other Procaviidae (Benoit, 2013) that were not included in our analysis. In both analyses, the early proboscideans Eritherium, Phosphatherium, Numidotherium tend to group with the non-proboscideans afrotherians. This means that neither the IV -Geometric morphometrics study of the bony labyrinths of proboscideans and afrotherians whole labyrinth morphology, nor the semicircular canals morphology allow to discriminate these taxa at the ordinal proboscidean level, at least based on the features measured with our landmark protocol. This suggests a high level of plesiomorphy in early proboscideans. This has yet to be tested with a phylogenetic analysis (see Chapter V) but we can assume based on these results that early proboscideans and P2 shows that the addition of the cochlear landmarks has significant influence on the analysis. In the analysis P1 with the cochlea, the Elephantidae does not form an exclusive cluster. The different specimens of Anancus are close to each other within the morphospace, but so are also other specimens of Loxodonta. By contrast, the analysis P2 restricted to the semicircular canals shows well distinct clusters. The early proboscideans form a cluster distinct from elephantimorphs. Prodeinotherium is located in a somewhat intermediary position between the two clusters. Within the Elephantimorpha, the Elephantidae forms a distinct cluster as well as all the Anancus specimens. Although some specimens are located closely to specimens from a different cluster (e.g., Platybelodon and the Elephantidae), there is no overlap of these clusters within the morphospace. This highlights the potential perturbation generated by the cochlear morphology. Within this particular taxa sample, it seems that the semicircular canals are more discriminant than the whole labyrinths. This is certainly due to the high level of intraspecific (and even intraProcavia capensis displays a very specialized morphology in our two analyses of the Afrotheria. This is explained mostly by the shape of its lateral canal. It expands posteriorly to the extent of crossing the plane defined by the posterior canals. Moreover, its insertion into the vestibule is located very high and close to the crus commune. This suggests that Procavia capensis is a peculiarly derived afrotherian which acquired many autapomorphies during evolution.

  A2 restricted to the semicircular canals of Afrotheria is the location of Arsinoitherium within the morphospace. It is

  latter study, Arsinoitherium is even found as the sister group of the clade (Moeritherium-Elephantimorpha) based on one homoplastic synapomorphy -the IV -Geometric morphometrics study of the bony labyrinths of proboscideans and afrotherians stocky aspect of the semicircular canalsof the semicircular canals). However, our results suggest that the shape of Arsinoitherium semicircular canals differs from the shape of elephantimorphs semicircular canals. It is closer to Numidotherium and to the new early embrithopod PM53. The axis PC1 best discriminates Arsinoitherium from the elephantimorphs. It is controlled by several features that can explain the difference between Arsinoitherium and elephantimorphs. First, the shape of the anterior semicircular canal tends to be modified along this axis. Indeed, the specimens located towards negative values display a rounder anterior semicircular canal while specimens located towards positive values display a more oval anterior canal. The angle between the major axis of this canal and the crus commune tends to be positive towards the positive values. The anterior semicircular canal of all studied elephantimorphs displays this morphology -oval, with a positive angle -with the exception of one Gomphotherium specimen (CBar coll. V2) which exhibits a round anterior canal. Noteworthy, the anterior canal of Palaeoloxodon displays a remarkably large angle between its major axis and the crus commune. On the other hand, all other studied afrotherians (including Arsinoitherium) display a round anterior canal. Another different trait is the aspect of the crus commune which is also controlled by axis PC1. It is thicker in elephantimorphs while it is more slender in other afrotherians. Arsinoitherium exhibits a relatively slender crus commune which explains its grouping with other afrotherians. The relative size of the lateral semicircular canal is also controlled by PC1 axis. The non-elephantimorph afrotherians tend to display relatively larger semicircular canals than the elephantimorphs. The lateral canal of Arsinoitherium is not particularly large (radius of curvature = 3.58) but compared to the vertical canals, it is relatively larger than in other elephantimorphs (except for two Elephas specimens, see Appendix 13). Finally, the location of the point of entry of the lateral canal into the vestibule is also controlled by PC1 axis. In Arsinoitherium and non-elephantimorphs it is high and close to the posterior ampulla, while it tends to be located lower in modern elephants. All these features contribute to make Arsinoitherium closer to non-elephantimorphs and suggest that it might be likely to separate them from proboscideans in cladistic analyses based on semicircular canals characters (see chapter V).

4 . 5 .

 45 Elephas specimens could not be discriminated from those of Loxodonta as well. The great level of variability found in the number of turns of the cochlea of Loxodonta explains the wide distribution of the specimens within the morphospace in E1. However, there is also significant variability in the semicircular canals because the analysis restricted to canals (E2) failed to discriminate Loxodonta from Elephas and also known Loxodonta cyclotis from known Loxodonta africana. In PCA, perspective, a between group analysis should be performed in the future to see if it allows completely discriminating African elephants from Asian elephants. Effect of the size While the analyses presented in this chapter were performed on the bony labyrinth shape, which is supposedly free of size, size can still influence the results via allometry. To investigate allometry, phylogenetic generalized least squared regressions were performed. Details about the method are given in the 'Material and Methods' section of this chapter ( § 2.2.). Regression parameters are given in Appendix 22 whereas adjusted R-squared and p-values are given in Table IV.3. To determine if size significantly influences values obtained on the principal components, one must look at the pvalues of the regression. If the p-value is inferior to 0.05, then the effect of size is significant (it means that the chances that size does not influence the principal component are less than 5%). The adjusted R-squared value gives an indication of how much of the variation is explained by the regression. In A1, the first PC is not significantly influenced by the size of the organisms (p-value = 0, size appears to slightly influence morphological variation IV -Geometric morphometrics study of the bony labyrinths of proboscideans and afrotherians depicted by PC2 and PC3 with R-squares of respectively 25% and 32%. In A2, only the first PC is significantly influenced by size, with an R-square of 38%. In P1, morphological variation along the first PC is not influenced significantly by size contrary to PC2 and PC3. In PC2, size drives almost all morphological variation with a R-square of 94%, while the effect is lower in PC3 (R-square of 48%). Finally, in P2, morphological variation along the PCs is influenced significantly by size. Size greatly influences the morphological variation along PC2 (R-square of 69%) and more moderately along PC1 (R-square of 42%) and PC3 (R-square of 25%).

3 .

 3 of this clade are located preferably towards the positive extremity of PC1 and PC2. Based on the observation of the deformations along the axes we identified the morphological trend of the members of this clade. They tend to display cochlea with more turns and that forms a larger angle with respect to the lateral canal plane. The axis of rotation of the apical turn of the cochlea tends to be offset with respect to the axis rotation of the basal turn. The area enclosed by the lateral canal is smaller and the semicircular canal is thicker in general. The crus commune tends to be shorter and thicker as well. The anterior and posterior canals are more oval and tend to display apical extensions. The angles between the lateral canals and the angle 279 IV -Geometric morphometrics study of the bony labyrinths of proboscideans and afrotherians between the posterior and lateral canals tend to decrease. Finally, the point of entry of the lateral canal into the vestibule is located higher with respect to the posterior ampulla. On the other hand, it was also possible to discriminate within the elephantimorphs the Elephantidae family in the analysis restricted to semicircular canals, but not in the analysis on the whole labyrinth. This suggests that only the semicircular canals characters are significant to characterize the elephantid family. Compared to the other elephantimorphs, the elephantids are located preferably towards the positive end of PC1 and the negative end of PC2. Therefore, the elephantids display thicker canals than in the other elephantimorphs, a lateral canal even smaller and a stockier crus commune. Moreover, they exhibit a point of entry of the lateral canal located lower with respect to the posterior ampulla. It was not possible using classic PCA analyses to fully discriminate the Asian elephants from the African elephants. Even though the Asian elephants form a limited cluster in both analyses, it always overlaps with the large cluster of the African elephants, highlighting the greater morphological variability of Loxodonta. Unexpectedly, this greater variability is not the result of the presence of two species within this genus, as the Loxodonta cyclotis specimens do not form a distinct group from Loxodonta africana in our analyses.

  and III. They help to define the phylogenetic characters used in our cladistic analysis of the proboscideans petrosal morphology (chapter V). They especially help to establish the primary homologies of the labyrinth characters.

  level of intraspecific variation in the proboscidean order, many features are constant at the species level and are therefore interesting to study in a phylogenetic perspective. The main objective of this chapter is to investigate the evolution of the inner ear and petrosal characters within the Proboscidea. To do so, a cladistic analysis is performed on the features that were defined in previous chapters. Phylogenetic analyses restricted on a narrow anatomical region are not appropriate to reconstruct phylogenetic relationships. Hence, we do not intend to review the proboscidean tree here. However, our study provides the opportunity to test the phylogenetic signal carried by the ear region of proboscideans. Except for the preliminary analysis of Schmitt & Gheerbrant (2016) on very few proboscidean taxa (Chapter I), this is the first detailed phylogenetic study of the petrosal characters of the proboscideans. A previous study (Benoit et al. 2013b) focused on the ear region of the Tethytheria, but only four proboscidean taxa are included in this work; of Eritherium was still unknown at the time. The cladistic analysis performed in Chapter V is substantially more exhaustive. It includes the inner ear anatomy of early taxa Eritherium and Phosphatherium, the deinotheriid Prodeinotherium, and 11 elephantimorph genera. Additionally, it includes newly defined characters and it takes into account the intraspecific variation. This chapter also extends the analysis at the larger scale of the afrotherians in order to evaluate the significance of the new petrosal characters identified in this work.

  , 2016) were defined as outgroups.The ingroup comprises proboscidean taxa described in chapters I to III. Eritherium and Phosphatherium are the earliest-

  and Stegomastodon) were all coded using new observations made in chapters II and III which brings the number of taxa to a total of 19 taxa (including outgroups).

  to Afrotheria. It is composed with the same 19 taxa used in the analyses focused on the Proboscidea to which 11 taxa have been added, bringing the total number of taxa to 30 (including outgroups). The V -Evolution of the ear region characters within the Proboscidea and the Afrotheria embrithopods are represented by Arsinoitherium (Court, 1990; Benoit et al. 2013b; new observations from Chapter III) and by the unpublished petrosal of a new Moroccan embrithopod (new observations from Chapter III). The sirenians are represented by Prorastomus and the isolated sirenian petrosal from Chambi (Benoit et al. 2013a; new observations from Chapter III). The hyracoids are represented by Seggeurius (Benoit et al.2016), Helioseus(Benoit, 2013) and Titanohyrax (2011) has also been coded and included in the analysis for identification. Finally, the late Cretaceous zalambdalestid Kulbeckia[START_REF] Ekdale | Petrosal bones of placental mammals from the Late Cretaceous of Uzbekistan[END_REF] Ekdale, 2013) was included as the outgroup taxon. We chose to add only fossil taxa to the analysis. Hence, while the Paenungulata is well represented in the taxa sample, only a few non-paenungulate afrotherians are represented.

  This character was used byBenoit et al. (2013b; character 23), but its states are modified here. The subarcuate fossa is a depression located on the cerebellar surface of the petrosal. It houses the paraflocculus of the cerebellum in life.Most mammals display a deep subarcuate fossa (0). A deep fossa can be spherical (e.g. Eritherium) or more conical (e.g.

  ) the subarcuate fossa is more superficial with no a clear outline or is even not distinct at all. The character states of the subarcuate fossa are illustrated in Fig V.1.

Figure V. 1 :

 1 Figure V.1 : Character 1, depth of the subarcuate fossa (cerebellar view), 3 states. A : state 0 (Eritherium azzouzorum); B: state 1 (Phosphatherium escuilliei, mirrored); C: state 2 (Elephas maximus, mirrored).

Figure V. 2 :

 2 Figure V.2 : Character 2, internal auditory meatus orientation, 2 states. A: state 0 (Eritherium azzouzorum); B: state 1 (Elephas maximus).

  houses the perilymphatic sac. The fenestra cochlea is an opening of the petrosal at the level of the scala tympani. In the early stages ontogeny, these two openings are not separated but instead form a unique perilymphatic foramen. This foramen generally divides into the aquaeductus cochleae and the fenestra cochleae later during ontogeny (state 0). However, some taxa retain the perilymphatic foramen in adult life (state 1). Illustrations of the character states are given in Fig V.3 below. The presence of the aquaeductus cochleae in the jugular fossa of the petrosal with a trumpet like shape in 3D models of the bony labyrinth clearly corresponds to state 0. A unique perilymphatic foramen is located near the crista interfenestralis (under the promontorium) and looks like a very large and elongated fenestra cochleae in 3D models of the bony labyrinth. The character was coded 0 in Eritherium based on the presence of a foramen in the jugular fossa that is very likely for the aquaeductus cochleae.

Figure V. 3 :

 3 Figure V.3 : Character 3, perilymphatic foramen, 2 states. A: state 0 (Phosphatherium escuilliei) ; B : state 1 (Gomphotherium angustidens). Caption: a.c. aquaeductus cochleae, f.c. fenestra cochleae, f.p. unique perilymphatic foramen.

5 .

 5 Shape of the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface The shape of the tegmen tympani was used in previous cladistic analyses such as Benoit et al. (2013b); however, we modified the coding to fit with the character states of the proboscideans. The shape of the tegmen tympani differs within mammals. Some taxa display a poorly developed tegmen tympani (state 0). In this case, the tegmen tympani is a small and uninflated bony structure. Some taxa exhibit a much more prominent tegmen tympani (state 1). The structure is inflated and can take different forms (tubular, kidney-shaped…). Finally, most of proboscidean taxa studied here displays a characteristic tegmen tympani. It is very prominent but rather flat and forms a large surface of bone on the cerebral surface of the petrosal (state 2). This surface is separated from the cerebellar surface by a more or less sharp ridge called the crista partis petrosa. Illustrations of the character states are given in Fig V.4.

Figure V. 4 : 6 .

 46 Figure V.4 : Character 5, shape of the tegmen tympani, 3 states. A: state 0 (Protungulatum ; modified after O'Leary 2010); B: state 1 (Eritherium azzouzorum); C: state 2 (Loxodonta africana). Caption: pr, promontorium.

Figure V. 5 :

 5 Figure V.5 : Character 6, hiatus Fallopii, 2 states. A, state 0 (Phosphatherium escuilliei); B: state 1 (Numidotherium koholense).

  sound transmission) or to reduce skull weight. For instance, the skull of some large mammals such as elephants is heavily pneumatized in order to lighten its weight. Pneumatic air cells of the petrosal are generally found in the most peripheral layers of bone, the center of the petrosal being generally very dense. Very large pneumatic cells are commonly found in the mastoid region of extant elephants (see chapter II). On the other hand, the inflated tegmen tympani usually exhibit pneumatic cells as well (e.g. Ocepeia and Eritherium). Finally, the pneumatic cells can be quite small and dispersed in the whole petrosal. Here, only the presence of pneumatic air cells is studied in this character. Taxa displaying pneumatization are all coded 1. Conversely, taxa lacking pneumatic cells in the petrosal are coded 0. Illustrations of the character states are given in Fig V.6 below.

Figure V. 6 :

 6 Figure V.6 : Character 7, petrosal pneumatization, 2 states. A: state 0 (Phosphatherium escuilliei); B: state 1 (Eritherium azzouzorum).

Figure V. 7 : 9 .

 79 Figure V.7 : Character 8, prootic sinus (cerebellar view), 2 states. A: state 0 (Loxodonta africana); B: state 1 ('Zhelestidae' petrosal after Ekdale et al.2004)

Figure V. 8 :

 8 Figure V.8 : Character 9, crista falciformis, 2 states. A: state 0 (Eritherium azzouzorum); B, state 1 (Phosphatherium escuilliei).

coded 1 .

 1 Illustrations of the character states are given in Fig V.9 below. A canal has been observed at the bottom of the subarcuate fossa of Ocepeia and Phosphatherium. The homology with the petromastoid canal is difficult to establish, however we decided to consider these canals to be homologous with the petromastoid canal based on their locations within the fossa. The presence of the canal in Phosphatherium was suggested by Benoit et al. (2013b) based on the observation of a foramen in the external subarcuate fossa. The CT investigation of the petrosal confirms the presence of a bony canal originating from this foramen.

Figure V. 9 :

 9 Figure V.9 : Character 10, petromastoid canal, 2 states. A: state 0 (Moeritherium) ; B: state 1 (Phosphatherium escuilliei). Caption: s.f. subarcuate fossa (or emplacement of the subarcuate fossa).

Figure V. 10 :

 10 Figure V.10 : Character 11, groove for the middle meningeal artery, 2 states. A: state 0 (Ocepeia daouiensis); B: state 1 (Gomphotherium angustidens). Caption: g.m.m.a. groove for the middle meningeal artery, t.t. tegmen tympani.

(

  state 1). This groove displays an anteroposterior course on the promontorial surface. Conversely, the transpromontory sulcus is absent in other taxa (state 0). Illustrations of the character states are given in Fig V.11. Specimens in which the promontorium is entirely broken are coded as missing data. The surface of the promontorium is not clearly observable in Platybelodon and the character was coded missing data for this taxon as well. The groove observed in Phosphatherium is located more medial than in other taxa displaying the transpromontory sulcus.

Figure V. 11 :

 11 Figure V.11 : Character 12, transpromontory sulcus, 2 states. A: state 0 (Loxodonta africana); B: state 1 (Numidotherium kohlense).

Figure V. 12 :

 12 Figure V.12 : Character 13, definition of the ampullae, 2 states. A: state 0 (Phosphatherium escuilliei); B: state 1 (Elephas maximus)

Figure V. 13 : 15 The

 1315 Figure V.13 : States of character 14 (basal thickening of the crus commune) illustrated in Phosphatherium escuilliei A: state 0 and Gomphotherium angustidens B: state 1.

Figure V. 14 :

 14 Figure V.14 : Character 15, thickness of the crus commune, 2 states. A: state 0 (Arsinoitherium zitteli); B: state 1 (Elephas maximus)

Figure V. 15 :

 15 Figure V.15 : Character 16, meeting point of the anterior and posterior canals, 2 states. A: state 0 (Arsinoitherium zitteli); B: state 1 (Mammuthus columbi)

Figure V. 16 :

 16 Figure V.16 : Character 17, shape of the anterior canal, 2 states. A: state 0 (Arsinoitherium zitteli); B: state 1 (Elephas maximus)

  below. This character has been used inBenoit et al. (2013b) as well. It is used here with the same coding.

Figure V. 17 :

 17 Figure V.17 : Character 18, shape of the posterior canal, 2 states. A: state 0 (Mammuthus columbi ); B: state 1 (Arsinoitherium zitteli)

Figure V. 18 :

 18 Figure V.18 : Character 19, extension of the anterior canal apex, 2 states. A: state 0 (Phosphatherium escuilliei); B: state 1 (Anancus arvernensis)

Figure V. 19 :

 19 Figure V.19: Character 20, point of entry of the lateral semicircular canal into the vestibule, 3 states. A: state 0 (Ocepeia daouiensis); B: state 1 (Cuvieronius sp.); C: state 2 (Elephas maximus)

Figure V. 20 :

 20 Figure V.20 : Character 21, shape of the cross-section of the canals, 2 states. A: state 0 (Ocepeia daouiensis); B: state 1 (Loxodonta cyclotis)

  Fig III.42) allowed us to determine two

Figure V. 21 :

 21 Figure V.21 : Character 22, thickness of the semicircular canals, 2 states. A: state 0 (Eritherium azzouzorum); B: state 1 (Loxodonta cyclotis)

Figure V. 22 :

 22 Figure V.22 : Character 23, relative size of the lateral canal, 3 states. A: state 0 (Tenrec); B: state 1 (Ocepeia daouiensis); C: state 2 (Mammut americanum)

  states are given in Fig V.23 below. This character could be considered an adaptation of character 27 from Benoit et al. (2013b), but with a heavily modified coding.

Figure V. 23 :

 23 Figure V.23 : Character 24, contact between the lateral and posterior canals, 3 states. A: state 0 (Eritherium azzouzorum); B: state 1 (Ocepeia daouiensis); C: state 2 (Cuvieronius sp. )

Figure V. 24 :

 24 Figure V.24 : Character 25, posterior expansion of the lateral canal, 2 states. A: state 0 (Loxodonta cyclotis); B: state 1 (Procavia capensis)

Figure V. 25 :

 25 Figure V.25 : Character 26, aspect ratio of the cochlea, 2 states. A: state 0 (Procavia capensis); B: state 1 (Loxodonta cyclotis)

Figure V. 26 : 28 .

 2628 Figure V.26 : Character 27, number of turns of the cochlea, 2 states. A: state 0 (Loxodonta cyclotis) ; B: state 1 (Procavia capensis )

Figure V. 27 :

 27 Figure V.27 : Character 28, lamina secundaria, 2 states. A: state 0 (Eritherium azzouzorum) ; B: state 1 (Loxodonta cyclotis)

Figure V. 28 :

 28 Figure V.28 : Character 29, relative volume of the cochlea, 2 states. A: state 0 (Ocepeia daouiensis); B: state 1 (Loxodonta cyclotis)

Figure V. 29 :

 29 Figure V.29 : Character 30, point of entry of the fenestra cochleae and the cochlear canaliculus within the scala tympani, 2 states. A: state 0 (Protungulatum sp., after Orliac & O'Leary, 2016); B: state 1 (Phosphatherium escuilliei)

Figure V. 30 : 32 .

 3032 Figure V.30 : Character 31, vestibulo-cochlear angle, 3 states. A: state 0 (Tenrec); B: state 1 (Ocepeia daouiensis); C: state 2 (Loxodonta cyclotis)

Figure V. 31 :

 31 Figure V.31 : Character 32, axis of rotation of the apical turn of the cochlea, 2 states. A: state 0 (Ocepeia daouiensis); B: state 1 (Elephas maximus)

  consistency index value. Such a value indicates homoplasy but also shows the presence of information in the tree. While the consistency index found in this analysis (CI = 0.493) is largely lower than in the analysis in Chapter I (CI = 0.905), the difference between the two retention indices is smaller (RI = 0.833 in the analysis of Chapter I and RI = 0.628 here). This highlights the conceptual differences between the two indices. Character indices are summarized in Appendix 26. In the analysis, the ingroup -Proboscidea -is not found monophyletic. Ocepeia, Protungulatum and Eritherium form a polytomy at the base of the tree (node 1). The locations of the transformations are illustrated in Fig V.32. The locations of the ambiguous transformations were fixed on a case-bycase basis, depending on the nature of the character; optimizations that seemed more plausible were favored. For most characters, the chosen optimization is ACCTRAN. Only four nodes are found in the strict consensus tree.

Figure V. 32 :

 32 Figure V.32 : Results of the cladistic analysis performed on the ear region characters of Proboscidea. Strict consensus of the 10,160 most parsimonious trees with location of the transformations. White dots: ambiguously located transformations. Grey dots: unambiguously located transformations. Black dots: unambiguously located transformations that display no homoplasy (RI=1). Black and white striped dots: ambiguously located transformations that display no homoplasy (RI=1). The upper number is the character number and the number between brackets is the character state.

(

  supporting node 2 are: the loss of the subarcuate fossa (character 1, 1→2, RI = 0.800), the transformation of a lateral canal entering into the vestibule at a high and close position to a high and distant position (character 20, 0→1, RI = 0.444) and the loss of the lamina secundaria (character 28, 0→1, RI = 1). Character 28 is non-homoplastic and character 1 display very few homoplasy but character 20 is highly homoplastic. The DELTRAN optimization of character 1 was already discussed in the precedent paragraph. The ambiguity of the transformation location of character 20 (0→1) is caused by the missing data in Moeritherium and Stegomastodon. We chose here to place the transformation at its earliest possible location. The ambiguity of the transformation location of character 28 (0→1) is caused by the missing data in Moeritherium. We chose to place the transformation at its earliest possible location because the loss of the lamina secundaria seems to happen early in proboscidean evolution. In fact, the lamina is not found in one of the two Numidotherium studied cochleae. supporting the node 2 are: the acquisition of a prominent and flat tegmen tympani (character 5, 1→2, RI = 1), the development of a deep groove likely for the middle meningeal artery on the cerebral surface of the tegmen tympani (character 11, 0→1, RI = 1), the thickening of both the crus commune (character 15, 0→1, RI = 0.500) and the semicircular canals (character 22, 0→1, RI = 0.750), the reduction of the lateral canal (character 23, 1→2, RI = 0.667) and the loss of contact between the posterior and lateral canals (character 24, 0→2, two steps, RI = 0.600). The first two characters (5 and 11) are non-homoplastic, while characters 15, 22, 23 and 24 display relatively moderate homoplasy. The ambiguity of the transformation location of character 5 (1→2) is caused by the missing data in Moeritherium. The transformation can be placed at nodes 2 or 3, but we chose to place it at node 3. Indeed, this node groups proboscideans that seem to display globally the same pattern of petrosal anatomy. The petrosal of Moeritherium display several features closer to early proboscideans (e.g. orientation of the internal auditory meatus). Hence the transformation is placed later at node 3. The same can be said about character the transformation location of character 11 is also caused by the missing data in Moeritherium. The crus commune thickness ratio of Moeritherium could not be calculated, however, the crus appears elongated and not very thick and Moeritherium would be certainly coded 0 if the crus was preserved enough. Hence, the transformation of character 15 is placed at node 3. The ambiguity of the transformation location of character 22 (0→1), 23 (1→2) and 24 (0→2) is caused by the missing data in both Moeritherium and Stegomastodon. They were not placed at node 4 because the existence of this node is highly improbable. Since Moeritherium displays a general anatomy that seems closer to earlier proboscideans than to elephantimorphs, the transformations were placed at node 3. Contrary to the other nodes, the node 4 is unusual as Stegomastodon is generally found as a gomphother close to other American genera such as Cuvieronius (Mothé et al. 2016a). This clade is only supported by two non-ambiguous synapomorphies that are homoplastic. The first synapomorphy is the re-acquisition of an anterior canal apex (character 19, 0→1, RI = 0.500), a feature lost in node 1 in this tree. The anterior canal apex is indeed absent in both studied ears of Stegomastodon. The second synapomorphy is the offset of the axis of rotation of the cochlear apical turn with respect the axis of the basal turn (character 32, 0→1, RI = 0.667) which is lost convergently in Platybelodon and Stegodon. polytomy due to a high level of homoplasy. Several synapomorphies of consensual groups are therefore depicted here as convergences. One example is the transformation from a high and distant to a low point of entry of the lateral canal into the vestibule (character 20, 1→2 RI = 0.444). This transformation appears as convergent autapomorphies of Elephas, Loxodonta, both Mammuthus species and Palaeoloxodon (5 steps) on the consensus tree. However, these taxa are all Elephantidae which is an undebated clade of proboscideans. If this clade had been found in our analysis, the transformation of character 20 (1→2) would have been one of its synapomorphy. The moderately high level of homoplasy of our tree prevents from getting a good resolution of the internal topology of the proboscideans and especially of the elephantimorphs.

Figure V. 34 : 5 .

 345 Figure V.34 : Mapping of character 2 (orientation of the internal auditory meatus) on the proboscidean tree. The evolution of the internal auditory meatus orientation within Proboscidea seems to be simple as well (Fig V.34). The vast majority of mammals display an internal auditory meatus with dorsally-oriented acoustical foramens. Indeed, the cranial nerves VII and VIII exit the meatus with a trajectory that is perpendicular to the cerebellar surface (state 0, see Fig V.2) hence directed dorsally. This plesiomorphy is retained in early proboscideans such as Eritherium, Phosphatherium, Numidotherium and Moeritherium. The orientation of the meatus is modified in the clade that

Figure V. 38 : 7 .

 387 Figure V.38 : Mapping of character 6 (hiatus fallopii ) on the proboscidean tree.

Figure V. 40 :Figure V. 41 : 7 (

 40417 Figure V.40 : Mapping of character 9 (crista falciformis) on the proboscidean tree.

Figure V. 44 :

 44 Figure V.44 : Mapping of character 13 (definition of the ampullae) on the proboscidean tree.

Figure V. 47 :::

 47 Figure V.47 : Mapping of character 16 (meeting point of the anterior and posterior canals into the crus commune) on the proboscidean tree.

Figure V. 56 :

 56 Figure V.56 : Mapping of character 26 (aspect ratio of the cochlea) on the proboscidean tree.

Figure V. 57 :

 57 Figure V.57 : Mapping of character 28 (lamina secundaria) on the proboscidean tree.

30 .

 30 Figure V.58 : Mapping of character 29 (relative volume of the cochlea) on the proboscidean tree. The evolution of the relative volume of the cochlea within Proboscidea is illustrated in Fig V.58. The cochlear volume is primitively superior to 55% (Ocepeia, Protungulatum). In Eritherium, the volume is inferior to 55% and in Phosphatherium the volume is superior. The state of this character in the ancestral morphotype of proboscideans is therefore

Figure V. 60 :

 60 Figure V.60 : Mapping of character 32 (axis of rotation of the apical turn of the cochlea) on the proboscidean tree.

  is not preserved enough to code this character in SMNS 47789-90 and it is difficult to evaluate the axis of rotation of the apical turn in the natural cochlear endocast of MNHN.F.LBE1 since it is partially covered by bony structures. The distribution of this character in the rest of proboscideans is ambiguous because of its great degree of homoplasy. The offset of the axis of rotation of the apical turn could be a synapomorphy of node 6 and the feature would be convergently lost in 78 steps. The strict consensus of these trees is given in Fig V.61 and displays a length of 119 steps. The retention index of the consensus tree (RI = 0.634) is very close to that observed in the analysis on the Proboscidea (RI = 0.628). Such a value indicates significant homoplasy but also shows the presence of information in the tree. The consistency index found in this analysis (CI = 0.286) is very low, but the conceptual limitations of this index have been already addressed in this chapter ( § 4.1.1.). Character indices are summarized in Appendix 28A. In the analysis, the ingroup -Afrotheria -is not found monophyletic. ambiguously-located: the loss of the subarcuate fossa (character 1, 1→2, RI = 0.71), the inflation of the tegmen tympani (character 5, 0→1, RI = 0.86), the development of a fallopian notch (character 6, 0→1, RI = 0.5), the reduction of the crista falciformis thickness (character 9, 0→1, RI = 0.75), the posterior canal that becomes oval (character 18, 0→1, RI = 0.3), the loss of the lamina secundaria (character 28, 0→1, RI = 0.85) and the decrease of the cochlear volume (character 29, 0→1, RI = 0.6). These transformations exhibit few to moderate homoplasy, at the exception of character 18 which is highly homoplastic. The node 3 contains all the previous taxa at the exception of Numidotherium and Prorastomus that form a polytomy at the base of the node. It is supported by five homoplastic synapomorphies and one non-homoplastic synapomorphy.

Figure V. 61 :

 61 Figure V.61 : Strict consensus of the 30 most parsimonious trees found in the unweighted analysis extended to the Afrotheria with a DELTRAN optimization. Length: 119; RI: 0.634. White dots: ambiguously located transformations. Grey dots: unambiguously located transformations. Black dots: unambiguously located transformations that display no homoplasy (RI=1). Black and white striped dots: ambiguously located transformations that display no homoplasy (RI=1). The upper number is the character number and the lower number is the character state.

4. 2 . 2 .

 22 Implied weighting analysis A second analysis of the same data set was developed using implied weighting to minimize the weight of the homoplastic characters. The resulting tree (Fig V.62) is compared with the previous tree ( strict consensus of these trees is given in Fig V.62 and displays a length of 95 steps which is less than for the unweighted analysis (119 steps). The retention index of the consensus tree (RI = 0.737) is better than for the unweighted analysis (RI = 0.634). This comes as no surprise since the homoplastic characters have less weight with the implied weighting method. Character indices are summarized in Appendix 28B. The analysis with implied weighting impacts the relationships within Afrotheria and within Proboscidea in the tree. First, the monophyly of the Afrotheria is obtained in the implied weighting analysis (node 2), contrary to the traditional analysis. It is supported by three homoplastic and ambiguously located transformations: a moderate subarcuate fossa (character 1, 0→1, RI = 0.78), a round anterior canal (character 17, 1→0, RI = 0.91) and the contact between the lateral and posterior canals that is only at the level of the posterior ampulla (character 24, 0→1, RI = 0.56). of them are not ambiguously located: the inflation of the tegmen tympani (character 5, 0→1, RI = 1), the development of a petrosal pneumatization (character 7, 0→1, RI = 0.2) and the decrease of the lateral canal relative size (character 23, 0→1, RI = 0.7). Within the Proboscidea, the location of Mammut is different between the two analyses. It is not found in the large polytomy anymore but considered more basal (node 8). This grouping is supported by three synapomorphies. The acquisition of the apical extension of the lateral canal (character 19, 0→1, RI = 0.42) and the offset of the cochlear apical turn axis of rotation (character 32, 0→1, RI = 0.57) are not ambiguously located but are homoplastic. The further decrease of the lateral canal relative size (character 23 1→2, RI = 0.7) is ambiguously located because of the missing data in Stegomastodon and Moeritherium. With the shift of Mammut, the Elephantida is found in the implied weighting tree (node 9). Stegomastodon is the only Elephantida excluded from this clade. In addition, the non-Elephantida Prodeinotherium is included in this node. The node 9 is supported by three synapomorphies: the hiatus Fallopii forms once more a discrete foramen (character 6, 1→0, RI = 0.5), the point of entry of the lateral canal into the vestibule is located high and distant from the posterior ampulla (character 20, 0→1, RI =1) and the lateral canal is not in contact at all with the posterior slender canal nor the posterior ampulla (character 24, 1→2, RI = 0.56). While the character 6 is ambiguously located, the character 20 and 24 are unambiguously located at this node. Moreover, the character 20 is non-), a lateral canal point of entry into the vestibule situated low and close to the posterior ampulla (character 20, 1→2, RI = 1) and a very high angle between the vestibule and the cochlea (character 31, 1→2, RI = 0.5). This node is hence well supported, with three not unambiguous synapomorphies, one of which is nonhomoplastic (character 20). Hence, the position of the lateral canal point of entry into the vestibule seems to be a strong character. A point of entry located low and close to the ampulla is therefore a 12). This comes as no surprise, because Palaeoloxodon was considered a subgenus of Elephas for a long time. However, recent reappraisals consider Palaeoloxodon to be a bona fide elephant genus[START_REF] Shoshani | Relationships within the Elephantinae using hyoid characters[END_REF]).Here the grouping of Palaeoloxodon and

Figure V. 62 :Finally

 62 Figure V.62 : Strict consensus of the 30 most parsimonious trees found in the implied weighting analysis extended to the Afrotheria with a DELTRAN optimization. White dots: ambiguously located transformations. Grey dots: unambiguously located transformations. Black dots: unambiguously located transformations that display no homoplasy (RI=1). Black and white striped dots: ambiguously located transformations that display no homoplasy (RI=1). The upper number is the character number and the number between brackets is the character state.

  petrosal and bony labyrinth characters within Proboscidea has been studied using several methods. The cladistic analyses allowed us to test the phylogenetic message carried by the ear region. It highlights some homoplasy of the petrosal and bony labyrinth characters. However, it was possible to discriminate several proboscidean groups using only characters of the auditory region and to identify the ear region characters that support these groupings. On the other hand, the character mapping on a consensual proboscidean tree allowed raising evolutionary hypotheses of morphological evolution on the current phylogenetic tree of the Proboscidea that was not recovered in our analysis. Thanks to these two approaches, we gain more insight into the evolution of the ear region within the Proboscidea. Our main evolutionary hypotheses are summarized in Fig V.63. The ear region morphotype of the extant elephants has not been acquired gradually during the evolutionary history of Proboscidea. Most of the key ear characters that define the elephant morphotype were already acquired by earlier F is probably the most important in terms of evolution of the ear region. It bears five major synapomorphies.

Figure V. 63 :

 63 Figure V.63 : Summary of the principal evolutionary hypotheses on the ear region of Proboscidea. Divergence dates and time ranges are approximated. The order of the transformations at a same node is not relevant. Only taxa studied in this work are represented. In dark grey: unambiguously located transformations. In light grey: ambiguously located transformations. R is for reversal. Clades: A) Tethytheria, B) Proboscidea, C,D,E,F) Unnamed clades, G) Elephantimorpha, H) Elephantida, I,J,K,L) Unnamed clades M) Elephantidae, N) Elephantini, O) Unnamed clade, P) Mammuthus genus.

Figure VI. 1 :

 1 Figure VI.1 : Semicircular duct system of Elephas maximus CEB150009, viewed in transparency within the bony labyrinth (A), in frontal view (B) and viewed in the plane of the lateral duct (C). Legends: a.a. anterior ampulla, a.c. anterior bony canal, a.s.d. anterior semicircular duct, a.u. anterior utricle, b.c.c. bony crus commune, c.c. crus commune, c.u. common utricle, l.a. lateral ampulla, l.c. lateral bony canal, l.s.d. lateral semicircular duct, l.u. lateral utricle, p.a. posterior ampulla, p.c. posterior bony canal, p.s.d. posterior semicircular duct, p.u. posterior utricle, s.c. simple crus.

Figure VI. 2 :

 2 Figure VI.2 : Different parts involved in the endolymphatic trajectories of the posterior (A), anterior (B) and lateral (C) membranous semicircular ducts of Elephas maximus. Legends: a.a. anterior ampulla, a.s. anterior slender duct, a.u. anterior utricle, c.a. crista ampullaris, c.c. crus commune, c.u. common utricle, l.a. lateral ampulla, l.s. lateral slender duct, p.a. posterior ampulla, p.s. posterior slender duct, p.u. posterior utricle, s.c. simple crus.

Figure VI. 3 :

 3 Figure VI.3 : Schematic representations of the endolymphatic flow (in red) in the anterior duct in views parallel (A) and perpendicular (B) to the duct, with a focus on the ampulla (C). The size of hair cells in panel C is exaggerated. Legends: c.a. crista ampullaris, c.h.a. crista hair cells, ci ciliae, cup cupula.

𝑑𝑑 2 𝑄𝑄

 2 𝑘𝑘 (𝑡𝑡) 𝑑𝑑𝑡𝑡² * 𝑀𝑀 𝑘𝑘 + 𝑑𝑑𝑄𝑄 𝑘𝑘 (𝑡𝑡) 𝑑𝑑𝑡𝑡 * 𝐶𝐶 𝑘𝑘 + 𝑄𝑄 𝑘𝑘 (𝑡𝑡) * 𝐾𝐾 𝑘𝑘 = 𝐺𝐺 𝑘𝑘 ����⃗ and 𝑄𝑄 𝑘𝑘 (𝑡𝑡) respectively correspond to volume acceleration, velocity and displacement of the endolymph at time t. M k is the mass parameter of the semicircular duct k. C k is the damping parameter of the semicircular duct k. K k is the stiffness parameter of the cupula k. 𝐺𝐺 𝑘𝑘 ����⃗ corresponds to a vector representing, by its direction, the axis of rotation that optimally displaces endolymph contained in the semicircular duct and by its magnitude, the inertial forcing parameter of the semicircular duct k.𝑑𝑑²𝛺𝛺 ��⃗ (𝑡𝑡)𝑑𝑑𝑡𝑡² is the vector of head angular acceleration at time t. in the duct during head motion.Rotation axes leading to such values are contained in a plane called the null plane.

  In this equation, 𝜌𝜌 represents the endolymph density (which is close to that of water), a k is the average cross-sectional area of the i-th part of the semicircular duct k and d sk is the length of the𝐶𝐶 𝑘𝑘 = � 𝜇𝜇 𝑒𝑒 (𝑇𝑇°𝐶𝐶) � 𝜆𝜆 𝜇𝜇𝑘𝑘,𝑖𝑖𝑠𝑠𝑘𝑘is used here to define the viscosity. λ μ represents the wall shape drag factor, which is influenced by the shape of the ducts in cross-section.

  parameters that are useful to define vestibular capacities of animals (following[START_REF] Rabbitt | Biomechanics of the semicircular canals and otolith organs[END_REF] David et al. in press):

  The lower the short-time constant, the faster the head rotation is encoded. It can be calculated with this equation: we said earlier, M k is influenced by the inverse of the average cross-sectional area of the duct a k . C k is even more influenced by the inverse of this measurement, because it is squared in the equation. Since most other morphological parameters get canceled in this equation, the short time constant is then only driven by the average crosssectional area of the duct. This highlights the importance of applying these calculations on measurements taken on the membranous ducts instead of the bony canals. Indeed, the average crosssectional area of the ducts can be very different than that of the bony canals, especially in large animals such as Elephas maximus (see Chapter II).

  corresponds to the degree of deflection of the ciliae per degree per second of head rotation. The higher the sensitivity, the more rotations are accurately detected, but the less the system can sustain high angular velocities without saturating (David, 2011). It can be calculated with this equation: , ε corresponds to the transfer factor for endolymph volume displacement to cilia deflection. ε is computed through finite element analysis in ARIADNE (David et al. in press), using a 3D model of the cupula inferred from the the membranous crista ampullaris. On the other hand, C k is extremely influenced by the average cross-sectional area of the ducts. Studying the membranous labyrinth is therefore crucial to the investigation of the sensitivity in mammals.

  differences of orientation of the ducts and therefore, the difference of orientation of their null plane. The anterior and posterior ducts detect head motions in pitch and roll rotations (Fig. VI.4A and VI.4C) while the lateral duct detects head motions in yaw rotations (Fig. VI.4B). Differences between the lateral and vertical canals capacities are taken into account in this chapter.

Figure VI. 4 :

 4 Figure VI.4 : Natural rotations of the head: pitch (A), yaw (B) and roll (C) in the skull of an elephant, with the petrosals seen in transparency.

  decimation and smoothing parameters to all specimens. The different anatomical regions of the membranous labyrinth were then manually separated following the David et al. (in press) protocol. At the end, the labyrinth is divided into eleven individual meshes illustrated in Fig. VI.5.

Figure VI. 5 :

 5 Figure VI.5 : Volume meshes of Elephas obtained at the end of the preparation protocol; Anterior (A), posterior (B) and lateral (C) slender ducts, anterior (D), posterior (E) and lateral (F) ampullae, crus commune (G), posterior utricle (H), common utricle (I), anterior utricle (J) and simple crus (K).

2. 2 . 5 .

 25 Landmark protocol Landmarks were then placed on the membranous labyrinths of Procavia, Elephas and Elephantulus following the protocol of David et al. (in press) and using AVIZO 7.1. Contrary to the bony labyrinth protocol (see 'Introduction' section of the thesis, § 2.2.), all the placed landmarks are internal here. A set of landmarks is placed along the central streamline of each semicircular duct (Fig. VI.6, orange sets). For the vertical ducts, the first landmark is placed at the intersection between the ampulla and the slender duct and the last landmark is placed at the intersection between the duct and the crus commune. For the lateral duct, the first landmark is placed at the intersection between the ampulla and the duct as well, but the last landmark is placed at the intersection between the duct and the simple crus. A set of landmarks is then placed along the streamline of the ampulla of each duct. The first landmark is placed at the intersection between the anterior utricle and the ampulla. The last landmark is placed at the intersection between the ampulla and the duct (Fig. VI.6, pale yellow sets).

Figure VI. 6 :

 6 Figure VI.6 : Landmarks sets of the membranous labyrinth of Elephas in general (A), posterior (B), lateral (C) and anterior (D) views. In orange, landmarks of the slender ducts; in pale yellow, ampullae landmarks; in blue; crus commune landmarks; in brown, simple crus landmarks; in green, anterior utricle landmarks; in purple, posterior utricle landmarks; in red, common utricle landmark.

Figure VI. 7 :

 7 Figure VI.7 : 3D baseline tridimensional model of the posterior cupula of Elephas maximus CEB150009 (A). 3D model of the middle crosssection of the posterior ampulla with the different stereociliae/kinociliae areas (B). In red, 0-30 µm, in yellow, 30-60 µm and in green, 60-90 µm.

(

  VGs ant + VGs post) * 0.707 2 * VGs lat In Elephantulus and Procavia, the ratio is close to 1, which means that sensitivity values are not significantly different for lateral and vertical motion. This implies that the angular velocities these two animals experiment in yaw are of the same order of magnitude as the angular velocities they experiment in roll and pitch. In contrary, Elephas exhibits a ratio that equals two, meaning that the sensitivity of its lateral duct is two times lower than the sensitivity of its vertical ducts. This implies that the angular velocities the elephant is able to experiment in pitch and roll are two times less important that in yaw. In contrary, the vestibular system of Elephas is two times more precise to discriminate angular rotations in pitch and roll than in yaw. In other terms, Elephas is capable of faster movements in yaw than in pitch and roll but can detect more precisely movements of its head in pitch and roll than in yaw. parameters are strongly influenced by the size (and/or body mass) of the animals. Large labyrinths tend to display higher short-time constants and sensitivities as well as lower natural VI -The semicircular duct system of the Proboscidea and the Afrotheria frequencies. In short, large animals tend to be less agile and display semicircular duct systems that respond more slowly to stimuli. Raw values remain interesting to discuss because they reflect real vestibular capacities of animals. However, to truly study adaptations of the semicircular duct system, we must suppress the effect of size. To do so, we used phylogenetic generalized least square regressions. They are presented in the 'Material and Methods' section ( § 2.2.8). Body-mass free values of our specimens and of the mammalian morphotype are given inTable VI.3.

  slower. The particularly low effective short time constants (effective functional parameters given in Table VI.2) are thus principally caused by the small size of the animal. Values for the lateral duct are similar to that of the vertical duct in Elephantulus; the slight reduction of the short time constant observed in the mammalian ancestral morphotype is not observed in Elephantulus. Hence, the lateral duct short time constant of Elephantulus is higher than

  similar to the mammalian ancestral morphotype for the lateral duct. Procavia therefore displays semicircular duct response speed within the same range of the mammalian ancestral morphotype. Thus, the low effective short time constants (Table VI.2) are mostly influenced by the small size of the animal. In Elephas, the short time constant values are different according to the ducts. The anterior duct exhibits the higher constant (6.4 ms) followed by the posterior duct constant (5.0 ms). The constant of the lateral duct is the lowest (3.9 ms). These values are high compared to the mammalian ancestral morphotype especially for the anterior duct (almost twice as high). The difference is slighter for the lateral duct. This shows that the very large size of Elephas is not the only factor that influences the particularly slow response speed of its semicircular duct system. At equal body mass, the vestibular system of Elephas displays particularly slow response speed to angular rotations compared to the mammalian ancestral morphotype. This is more pronounced in pitch and roll motion than in yaw.

ancestral morphotype is very close to 1 (

 1 0.91) which means it displays a very similar sensitivity in all three ducts. Hence the angular velocities the mammalian ancestral morphotype experiments in yaw are of the same order of magnitude as the velocities it experiments in roll and pitch.

Figure VI. 8 :

 8 Figure VI.8 : Body mass-free inferred short time constant (T 2 ) of afrotherians for the lateral duct (A) and vertical ducts (B). Values are in ms.

Figure VI. 9 :

 9 Figure VI.9 : Body mass-free inferred natural frequency (ω 0 ) of afrotherians for the lateral duct (A) and vertical ducts (B). Values are in Hz.

  proboscideans display adaptations of the lateral duct to compensate their large size, or that the lateral ducts of Prorastomus, Procavia, Elephantulus and the early embrithopod are poorly adapted to experience relatively high angular velocities for yaw rotations. Within the Proboscidea, Mammuthus columbi and Stegodon display slightly lower sensitivity values, probably making them the taxa experiencing the higher angular velocities for yaw rotation of our sample, if the effect of size is eliminated. On the other hand, Elephantulus displays the highest body mass-free sensitivity. The distribution of body-mass free sensitivity values for the vertical ducts is different than for the lateral duct (Fig VI.10B). Early proboscideans (Eritherium and Phosphatherium) and Ocepeia display the lowest body mass-free fitted sensitivities of the sample which means that they are probably experiencing the highest angular velocities in pitch and roll motion when the effect of size is eliminated. A second functional group is composed of Prorastomus, Prodeinotherium, Tenrec, Numidotherium and Loxodonta africana. They display higher fitted sensitivities hence probably experience lower angular velocities in pitch and roll. Platybelodon is slightly less sensitive for these types of motion and similar to Procavia. Palaeoloxodon, Mammuthus primigenius, Arsinoitherium, Anancus and Stegodon display body massfree values similar to Elephantulus and higher than previous taxa. The other proboscideans all display even higher sensitivity values which means that even without the influence of size, they are experiencing lower angular velocities during pitch and roll motion than the other afrotherians.

Figure VI. 10 :

 10 Figure VI.10 : Body mass-free inferred sensitivity (VGs) of afrotherians for the lateral duct (A) and vertical ducts (B). Values are in mdeg/deg.s -1 .

Figure VI. 11 :

 11 Figure VI.11 : Mapping of the fitted short time constant (T2) of the lateral duct (A) and the vertical ducts (B) on the afrotherian tree. Values are in ms.

Figure VI. 12 :

 12 Figure VI.12 : Mapping of the fitted natural frequency (ω0) of the lateral duct (A) and the vertical ducts (B) on the afrotherian tree. Values are in Hz.

Figure VI. 13 :

 13 Figure VI.13 : Mapping of the fitted sensitivity (VGs) of the lateral duct (A) and the vertical ducts (B) on the afrotherian tree

  5 km but vocal recognition of family and bond group members is usually achieved in smaller distances (McComb et al. 2003). It has been demonstrated that elephant vocalizations produce Rayleigh waves, a type of ground surface wave (O'Connell et al. 1997). The ossicular chain morphology of elephants is suitable for sensing ground vibrations (Reuter & Nummela, 1998). Moreover, O'Connell-Rodwell et al. (2001) suggest that elephants may use bone conduction in order to hear low-frequency sounds. All of these considerations imply that long-range infrasound callings are transmitted via ground surface waves. This is confirmed by O'Connell-Rodwell et al. (2006) and reviewed in O'Connell-Rodwell (2007). The low frequency sounds are produced thanks to flow-induced vocal fold vibrations (Herbst et al. 2012; 2013). While extant elephants are clearly low-frequency hearing specialists, extinct taxa do not necessary display the same pattern. Indeed, Court (1992) suggests that Numidotherium was not able to hear low-frequency sounds, based on the morphology of its cochlea. The objective here is to conduct a preliminary study of the auditory capacities of extinct proboscideans based on their bony labyrinth morphology. These considerations are helpful to make hypotheses on the evolution of lowfrequency hearing within the Proboscidea.

𝑓𝑓 = 1 .

 1 507 exp [-0.578(ρ -1)]

  cochlea is given by the ARIADNE add-on currently developed by Romain David and based on cochlear landmarks (for more details, see the main 'Material and Methods' section of the thesis). The numbers of turns has been calculated with the protocol of West

  capacities of the animal to hear low frequencies. The presence of an undivided perilymphatic foramen in an extinct mammal is another hint at its capacities of hearing low frequency sounds. The distribution of the perilymphatic foramen among proboscideans is therefore studied here to discuss the evolution of hearing within Proboscidea. VII -Preliminary considerations on the auditory capacities of proboscideans This means that it was probably more capable of hearing low frequencies with its left ear than with its right ear. Platybelodon displays a relatively small value compared to other proboscideans but it falls in the group supposedly adapted to hear low-frequency sounds. Prodeinotherium, Stegomastodon and Stegodon exhibit slightly higher values. Mammut and Mammuthus exhibit rather average values. The two specimens of Gomphotherium display relatively different products, MNHN.F.SEP38 being relatively average and CBar coll. V2 displaying the higher value observed in proboscideans (236). Anancus specimens, as well as Elephas, tend to display relative high values. Loxodonta cyclotis tends to display greater values than L. africana even though one L. cyclotis specimen is rather in the middle range (MNHN.AC.ZM.1950-523). However, except for the probably pathological ear of MNHN.AC.ZM.2008-71, Loxodonta specimens exhibit a great variety of values (142 to 214) which covers almost the entire sample. The values used here reflect the relatively high level of cochlear variability among extant elephants -and probably proboscideans in generalhighlighted in Chapter II. The mechanisms of low-frequency hearing in elephants remain poorly understood and certainly are multifactorial. The negative influence of a shorter cochlea displaying less turns on low-frequency hearing could be compensated by variations of other ear features such as the ossicular chain or the spiral ganglion.

  Fig. VII.2 (see also Appendix 31). As said in the 'Material and Methods' section ( § 2.2.2.), the results obtained here are approximated and should only be discussed in terms of tendencies. It appears that Ocepeia and early proboscideans Eritherium and Numidotherium have a low frequency limit superior to 100 Hz. They definitely do not display the adaptations to low-frequency hearing observed in extant elephants. The estimated low-frequency limit of Eritherium is the highest of the sample (ca. 168 Hz) which means that is even less adapted to low-frequency hearing than Ocepeia and Numidotherium. Finally, the elephantimorphs and deinotheriids all display very low low-frequency limits (between 6.6 and 27.1 Hz).

  First, as previously discussed, there is a significant difference between the values found in the right and left ears of Loxodonta specimen MNHN.ZM.AC.2008-71. While the lowfrequency limit of the left ear is estimated to be 14.5 Hz, the low-frequency limit of the right is 27.1 Hz. This suggests that this specimen was able to hear infra-sounds only with its left ear. However, the values are too approximated to really discuss about infra-sound hearing in this functional group. The only proboscidean taxa that are unable to hear infra-sounds according to our results are Eritherium, Numidotherium and Platybelodon. While Eritherium and Numidotherium seem undoubtedly unable to hear infra-sounds (low-frequency limits of 167.7 Hz and 127.7 Hz respectively), the approximation of our results prevent us from drawing conclusions about Platybelodon (lowfrequency limit of 22.3 Hz).

  secundaria) is primitively present in eutherian mammals and even in afrotherians. Ocepeia displays a lamina secundaria. The loss of this spiral lamina is present in almost every studied proboscidean. Only Eritherium and Phosphatherium unarguably exhibit a secondary bony lamina. The information is missing concerning Moeritherium and the presence of a lamina secundaria in Numidotherium appears to be variable. It is absent in the unlabeled specimen segmented by Benoit et al. (2013b) and in UOK5 (described here). However, a lamina secundaria is visible on the natural endocast described in Court (1992). As previously said (in the 'Material and VII -Preliminary considerations on the auditory capacities of proboscideans Methods' section of this chapter), the loss of the secondary bony lamina probably correlates with low-frequency hearing.

  V.35, Chapter V). On the other hand, early proboscideans Eritherium, Phosphatherium and Numidotherium do not display such feature. This anatomical feature provides another hint that suggests that early proboscideans were not low-frequency hearing mammals. The adaptation to low-frequency would thus appear in the clade that includes Moeritherium, the deinotheriids and the elephantimorphs.

3 .

 3 The information given by the three different proxies appears to be congruent.The estimated low-frequency limits suggest that early proboscideans were not able to hear low frequencies (Fig.VII.3A).Conversely, all elephantimorphs and deinotheriids seem to be adapted to lowfrequency hearing. The apparition of this adaptation is ambiguous and is therefore a synapomorphy of the clade (deinotheriidselephantimorphs) or the clade that includes Moeritherium, deinotheriids and elephantimorphs. Similar conclusions are suggested by the distribution of the lamina secundaria among elephantimorphs (Fig VII.3B). However, it should be noted that the presence of the lamina secundaria has been documented only in one Numidotherium specimen. -frequency hearing that would appear in the clade containing Moeritherium, the deinotheriids and the elephantimorphs (Fig VII.3C). These observations confirm the results of the previous chapters. The modern elephantine morphotype of the ear region seems to have been already acquired in Prodeinotherium (and maybe even Moeritherium) and is generalized in elephantimorphs. Such hypotheses are also supported by the geometric morphometrics analysis and the functional study of the semicircular canals. In this case, the modern morphotype seems to be linked with low-frequency hearing, which is a condition that is probably generalized in elephantimorphs, in Prodeinotherium and maybe even in Moeritherium. However, it should be noted that the considerations made in this chapter are only preliminary. The singular auditory capacities of extant elephants (infra-sound hearing abilities) deserve a further study. The evolution of this striking feature remains poorly investigated here, because of too approximated low-frequency limit calculations. On the other hand, the hearing capacities depend on more features than those studied here. Further investigations of the ossicular chain of extant and extinct proboscideans would be of great interest to complete the preliminary work presented here. Phosphatherium escuilliei provides key data about the ancestral morphotype of the Proboscidea. It shows that the ancestral state of the proboscidean ear region was not specialized but was rather generalized and close to the morphology of other paenungulates and afrotherians. The petrosal of extant elephants is solidly fused in the skull and therefore difficult to access. While this region has already been described in the past, the ancient studies fail to provide most of the anatomical considerations taken into account in recent studies of the petrosal and inner ear of mammals. Our anatomical description of the ear region of extant elephants using modern investigation technical tools such as the CT scan provides the first comprehensive study of this structure in one of the most emblematic mammals. The petrosal and bony labyrinth of the three extant elephant species are illustrated and compared, but no striking specific features could be discriminated. The comparison of several specimens of the same species shows some level of intra-specific variability in both the petrosal and the bony labyrinth. Moreover, the segmentation of the right and left ears of the same specimen of an African elephant shows a singular case of intra-individual variability that is likely pathological: the number of turns of the cochlea displays a difference of half a turn between the right and left ears. The intra-specific variability of extant elephants evidenced in this work allows refining the description of extinct proboscidean taxa and the definition of the phylogenetic characters of the petrosal. This study is the first to document the morphological diversity of the petrosal and inner ear of extinct proboscidean taxa. The region is described in sixteen genera (including extant ones), covering most major proboscidean groups. Comparisons with other afrotherians and considerations about the intra-specific variation help to identify some problematic phylogenetic characters and to define a pertinent coding. On the other hand, several new phylogenetic characters General conclusions and perspectives are proposed here, such as the definition of the bony ampullae, the position of the lateral canal insertion with respect to the posterior ampulla, the orientation of the internal auditory meatus, and quantitative ratios are used to define characters measuring the thickness and relative size. Proboscidea shows that the modern morphotype exhibited in extant elephants is acquired gradually in the first stages of proboscidean evolution but generalized in the clade that includes deinotheriids and Elephantiformes. The definition of new phylogenetic characters allows defining new synapomorphies of emblematic groups of proboscideans (e.g. a lateral canal insertion located low and close to the posterior ampulla appears to be a synapomorphy of the Elephantidae). Thanks to an original method (David et al. in press), we were able to study the functional capacities of the vestibular system of proboscideans. Extant elephants display a poor level of agility, especially compared to other afrotherians such as Elephantulus. However, the semicircular duct capacities are dependent of size. When the effect of size is eliminated, Elephas actually displays better functional capacities than predicted. We suggest that extant elephants compensate their large size with the morphology of their semicircular duct. Reductions of the duct volume and of the lateral duct radius seem to be adaptations allowing Elephas to compensate the disadvantage due to its large size. On the other hand, inferences on the semicircular canals of extinct proboscideans confirm the existence of a key evolutionary stage of the ear region in this group. Indeed, the functional capacities exhibited in extant elephants appear to have been the locomotor and auditory capacities of proboscideans. The congruence of these data strongly supports the idea that the modern morphotype exhibited in extant elephants was already acquired in Prodeinotherium and generalized in elephantimorphs and that those features were selected for their functional implications. Several areas of work need further studies. Given the difficulty to scan large skulls of elephants, the study of the intraspecific variation in extant species remains based on a low number of specimens. The sample expansion would allow testing the variability with statistical methods and making considerations on the ontogenetic variability of the inner ear and petrosal characters. On the other hand, be tested to see if it allows discriminating Elephas from Loxodonta, and even Loxodonta cyclotis from Loxodonta africana. The segmentation of the membranous labyrinths of other afrotherians such as the sirenians would allow us to calibrate the functional inferences even more and to make assumptions on the controversial lifestyle of early proboscideans. Finally, the preliminary study of the audition in the Proboscidea should be expanded. Indeed, a complete and connected ossicular chain is preserved in one of the studied extant specimens as well as isolated ossicles in Anancus and other extant elephants. A morpho-functional study of the ossicles is therefore envisaged in the future. The study of the preserved membranous cochlear duct in one specimen of Elephas should allow us to draw more precise conclusions on the audition of extant elephants and to infer the morphology of the duct in extinct species. Hopefully, these considerations would shed new lights on the evolution of audition in the Proboscidea and specifically on the development of lowfrequency hearing in this emblematic modern order of mammals.

TABLE OF CONTENTS

 OF

	INTRODUCTION
	1. Context, concepts and objectives
	2. Material and methods
	2.1. Material
	2.2. Methods
	CHAPTER I -

The ear region of earliest known elephant relatives: new light on the ancestral morphotype of proboscideans and afrotherians

  Comparison of the petrosal morphology of Eritherium and Phosphatherium 4.2. Cladistic analysis of petrosal and inner ear features of Eritherium and Phosphatherium among Proboscidea 4.3. Significance of Phosphatherium and Eritherium for understanding petrosal character evolution among Placentalia, Afrotheria and Proboscidea 5. Conclusion CHAPTER

	1. Introduction
	2. Material and methods
	2.1. Material studied
	2.2. CT scanning acquisition
	2.3. Measurements
	2.4. Abbreviations
	3. Systematic descriptions
	3.1. Eritherium azzouzorum Gheerbrant, 2009
	3.2. Phosphatherium escuilliei Gheerbrant et al. 1996
	4. Discussion
	4.1.

II -Petrosal and inner ear anatomy of extant elephants

	1. Introduction
	2. Material and methods
	2.1. Material
	2.2. Methods
	3. Anatomical descriptions
	3.1. The auditory region and its location in the skull
	3.2. Petrosal
	3.3. Ossicles
	3.4. Labyrinth
	3.4.1. Loxodonta sp
	3.4.2. Elephas maximus
	4. Discussion
	4.1. Intraspecific variability
	4.2. Intra-individual variability
	4.3. Constant similarities between Elephas and Loxodonta
	4.4. Differences between Elephas and Loxodonta
	4.5. Differences between the two African species
	5. Conclusion
	CHAPTER III -

Anatomy of the ear region of fossil proboscideans: comparisons with extant elephants and close relatives

	3.2.3. Prodeinotherium bavaricum
	3.2.4. Mammut americanum
	3.2.5. Gomphotherium angustidens
	3.2.6. Cuvieronius sp.
	3.2.7. Stegomastodon sp
	3.2.8. Platybelodon grangeri
	3.2.9. Anancus arvernensis
	3.2.10. Stegodon orientalis
	3.2.11. Mammuthus
	3.2.12. Palaeoloxodon antiquus
	4. Comparisons
	4.1. Petrosal
	4.2. Inner ear
	5. Conclusion
	CHAPTER IV -
	1. Introduction
	2. Material and methods
	2.1. Taxa sample
	2.1.1. Non-proboscideans
	2.1.2. Proboscideans
	2.2. Methods
	3. Systematic descriptions
	3.1. Outgroups
	3.1.1. Ocepeia daouiensis
	3.1.2. Unnamed Embrithopoda from the Ypresian of Morocco
	3.2. Proboscideans
	3.2.1. Numidotherium koholense
	3.2.2. Moeritherium lyonsi

Geometric morphometrics study of the bony labyrinth of proboscideans and afrotherians using 3D semi-landmarks

	1. Introduction
	2. Material and methods
	2.1. Taxa sample
	2.2. Methods
	3. Results
	3.1. Analysis of the Afrotheria
	3.1.1. Analysis A1 of the whole labyrinth
	3.1.2. Analysis A2 restricted to the semicircular canals
	3.2. Analysis of the Proboscidea
	3.2.1. Analysis P1 of the whole labyrinth
	3.2.2. Analysis P2 restricted to the semicircular canals
	3.3. Analysis of extant elephants
	3.3.1. Analysis E1 of the whole labyrinth
	3.3.2. Analysis E2 restricted to the semicircular canals
	4. Discussion
	4.1. Impact of the addition of cochlear landmarks
	4.2. Procavia capensis, a derived afrotherian
	4.3. Differences between the bony labyrinth of Arsinoitherium and elephants
	4.4. Loxodonta cyclotis VS Loxodonta africana
	4.5. Effect of the size
	5. Conclusion
	CHAPTER V

-Evolution of the ear region characters within the Proboscidea and the Afrotheria

	1. Introduction
	2. Material and methods
	2.1. Taxon sampling
	2.1.1. Proboscidea
	2.1.2. Afrotheria
	2.2. Methods
	2.2.1. Cladistic analysis performed on the Proboscidea

Table 2 :

 2 List of the taxa scanned during this PhD thesis with indications on their collection number, the location of where they were scanned, the model of the scanner and the resolution used during the acquisition. AMNH stands for American Museum of Natural History; AST-RX stands for Accès Scientifique à la Tomographie à Rayons X; GEIT stands for General Electronics Inspection Technologies; MNHN stands for Muséum national d'Histoire naturelle; MPI-EVA stands for Max Planck Institute for Evolutionary Anthropology; NHMUK stands for Natural History Museum of the United Kingdom.

	Order	Genus	Species	Collection number	Scanning platform and scanner	Voxel size (µm)
	Proboscidea	Eritherium	azzouzorum	PM88	AST-RX (MNHN) v¦tome¦x L240 (GEIT)	10.1
	Proboscidea	Phosphatherium	escuilliei	PM17	AST-RX (MNHN) v¦tome¦x L240 (GEIT)	38.6

Proboscidea Elephas maximus MNHN.ZM.AC.1904-273 AST-RX (MNHN) v¦tome¦x L240 (GEIT) 79.27(l) 73.26(r) Introduction

Table I . 1 :

 I1 Measurements of the bony labyrinths of Eritherium and Phosphatherium. ? indicates unknown states.

  The main features of both taxa are compared and summarized in greater detail in Table I.2.

			I -The ear region of earliest known elephant relatives
	4. Discussion
	4.1. Comparison of the petrosal morphology of Eritherium and Phosphatherium	We compared the petrosal and inner ear characters of Eritherium and
	Although	Eritherium	and	Phosphatherium with other proboscideans
	Phosphatherium are both basal primitive	and also among various afrotherians,
	Proboscidea, the anatomy of their ear differences in both middle and inner ear regions differs markedly. They display	1.57 placentals and primitive eutherians and 1.62 cochlea 2 >1 Number of turns of the therians (e.g. zhelestids and
	structures.	The	most	remarkable	Length of the cochlea (mm)	14.13	?
	difference is seen in the depth of the fossa	(%) Relative cochlear volume	45	25
						Cochlear aspect ratio	0.35	>0.41
						Lamina secundaria depth (mm)	0.1	0.07
						Length of the crus commune (mm)	>2.26	2.57
						Anterior canal radius of curvature	1.53	1.74
						Lateral canal radius of curvature	1.36	1.41
						Posterior canal radius of curvature	1.36	1.66
						Angle between anterior and posterior canals (°)	92	91
						Angle between anterior and lateral canals (°)	87	76
						Angle between lateral and posterior canals (°)	90	85
						Mean of the angles (°)	89.8	84

subarcuata; Eritherium has an extremely deep fossa, whereas it is much more moderate in Phosphatherium (with some individual variation). In addition, the fossa subarcuata of Phosphatherium is larger and longer antero-posteriorly. The tegmen tympani of Eritherium is strongly inflated and displays an ossified canal for the ramus superior of the stapedial artery, whereas in Phosphatherium the tegmen tympani is not inflated, and it does not possess a canal for the superior ramus of the stapedial artery. The lateral and posterior semicircular canals of Phosphatherium are fully merged, thus forming a true crus commune secundaria, whereas they are only partly merged in Eritherium. In general, the semicircular canals in Eritherium are larger than those of Phosphatherium.

Table I . 2 :

 I2 Comparisons of the main features of the ear region of Eritherium and Phosphatherium. ? is for unknown states.

		Eritherium	Phosphatherium
	Fossa subarcuata	Very deep	Moderately deep but wider antero-posteriorly
	Fenestra cochleae and cochlear aqueduct	Probably not merged into a unique perilymphatic foramen	Not merged into a unique perilymphatic foramen
	Stapedial ratio	1.57	1.62
	Size of the fenestra vestibuli	Large	Small
	Promontorium shape	Rather flat	Bulging
	Inflation of the tegmen tympani	Strong	Absent
	Stapedial sulcus	Absent	Absent
	Transpromontory sulcus	Absent	Absent
	Superior ramus for the stapedial artery	Located in an ossified canal	Absent
	Prootic sinus	Present	Absent
	Pneumatization of the petrosal	Present	Absent
	Cross-section of the semicircular canals	Round	Round
	Crus commune secundaria	Partial	Present
	Semicircular canal aspects	Slender	Slender
	Cochlear aspect in profile	Planispiral	? (broken)
	Number of turns of the cochlea	2	? (broken but >1)

Table I . 3 :

 I3 Comparison of some major described characters of the petrosal and inner ear of the early proboscideans Eritherium and Phosphatherium among eutherians and placentals, and inferred ancestral state optimization. Sources: Macroscelidea represented by Chambius(Benoit et al. 2013c), Afrosoricida represented by Potamogale

Fossa subarcuata (1) Undivided perilymphatic foramen (2) Shape of the fenestra vestibuli (3) Size of the fenestra vestibuli (4) Crus commune secundaria (13) Thickness of the semicircular canals (14) Number of turns of the cochlea (17) Lamina secundaria (18) Henkelotherium

I -The ear region of earliest known elephant relatives

Table II .

 II

1 : Extant elephants taxa sample. 'L' is for left, 'R' is for right. 'Ossicles column' references the ossicles preserved in the middle ear. 'M' is for malleus, 'I' is for incus, 'S' is for stapes,'-' is for none. In the provenance column, '-' is for missing data.

Table II .3: Stapedial ratio of extant elephants Taxon Specimen Ratio

 II

	II -Petrosal and inner ear anatomy of extant elephants
	The fenestrae of Elephas specimen
	1904-273 and Loxodonta specimen 1950-
	278 are slightly more oval than the other
	specimens (ratio of 1.8). In contrast, the
	fenestra vestibuli of Elephas specimen
	2008-81 and Loxodonta specimen 1861-53
	are slightly rounder (ratio of 1.6).
	Elephas	1904-273	1.8
	Elephas	1941-209	1.7
	Elephas	2008-81	1.6
	Elephas	CEB 150009	-
	Loxodonta	1861-53	1.6
	Loxodonta	1932-523	1.7
	Loxodonta	1950-278	1.8
	Loxodonta	1956-194	-
	Loxodonta	1957-465	1.7
	Loxodonta	1961-69	1.7
	Loxodonta	2008-71L	1.7
	Loxodonta	2008-71R	1.7
	Loxodonta	CEB130168	1.7
	66

Figure II.9 : Ventral

  view of the petrosal. Promontorium without the posterior bulge (A, L. cyclotis MNHN.ZM.AC.1957-465) and promontorium with the posterior bulge (B, Elephas MNHN.ZM.AC.2008-81). Legends:

bu posterior bulge, c.i. crista interfenestralis, e.w. epitympanic wing, f.v. fenestra vestibuli, pr promontorium.

	In 1861-53, there is a cavity located
	near the inflation. In Loxodonta 2008-71
	(left and right side) the inflation is extreme
	and displays a bean-shaped protuberance.
	The protuberance is present in Loxodonta
	1956-194 and 1950-278 but is less
	developed than in 2008-71. The
	investigation of the protuberance through
	the microtomographic slices reveals no
	peculiar internal structure.

Figure II.10 :

  Variations of the protuberance located closely to the promontorium in medial view. (A) No protuberance (Elephas MNHN.ZM.AC.1941-209), (B) slight protuberance (L. cyclotis MNHN.ZM.AC.1956-194), (C) very inflated protuberance (Loxodonta sp MNHN.ZM.AC.2008-71, right ear).

	Legends:	e.w.	epitympanic	wing,	pr	promontorium,	prot	protuberance.

Table II . 3 :

 II3 Measurements of the semicircular canals of extant elephants

			II -Petrosal and inner ear anatomy of extant elephants
	The angle between the anterior
	and posterior semicircular canals varies
	between the species. In Elephas maximus,
	Crus commune length (mm) the variation is minimal (from 72.6° to Crus commune section radius (mm) Crus commune thickness ratio ASC length (mm) PSC length (mm) 78.9°) but it is more pronounced in Loxodonta. Indeed there are specimens displaying very acute canals (Loxodonta sp. MNHN.ZM.AC.1932-523 with 70.9°) while other specimens display larger angles (L. africana CEB130168 with 84.8°	LSC length (mm)	SCC average thickness ratio	Angle ASC-PSC (°)	Angle ASC-LSC (°)	Angle PSC-LSC (°)	ASC radius of curvature	PSC radius of curvature	LSC radius of curvature
	Elephas 1904-273	7.11	1.51 21.19 22.45 22.44 20.33 4.64	72.6	75.7	88.8	5.25	5.20	3.16
	Elephas 1941-209	5.58	1.20 21.53 22.79 22.49 23.06 4.13	76.5	74.2	83.2	5.19	5.23	3.52
	Elephas 2008-81	6.53	1.48 22.62 26.66 24.56 26.07 3.52	76.6	75.0	85.8	5.97	5.60	4.06
	Elephas	3.07	1.51 49.20 23.47 21.01 24.10 4.86	78.9	67.9	85.7	5.04	4.65	3.65
	CEB150009
	Loxodonta 1932-523	5.47	1.38 25.26 24.99 23.65 21.26 3.02	70.9	72.4	85.8	5.66	5.37	3.21
	Loxodonta 2008-71	5.63	1.13 20.09 22.49 22.31 22.54 3.90	75.9	59.8	83.5	5.18	5.14	3.56
	L. africana 1861-53	5.50	1.82 27.27 27.42 24.36 21.04 3.57	81.1	73.8	82.2	5.86	5.25	3.54
	L. africana	4.05	1.51 37.23 27.44 25.40 24.07 3.28	84.8	72.7	78.0	5.80	5.55	3.72
	CEB130168
	L. cyclotis 1950-728	5.89	1.64 27.87 23.85 21.40 21.06 3.69	83.3	72.3	88.5	5.41	4.91	3.35
	L. cyclotis 1956-194	5.37	1.57 29.20 31.98 29.92 23.44 2.74	76.7	72.9	93.8	6.87	6.25	4.09
	L. cyclotis 1957-465	4.84	1.94 40.15 23.99 21.88 20.50 4.01	74.7	80.0	85.0	5.48	4.98	3.15
	L. cyclotis 1961-69	4.46	1.40 31.33 22.30 20.61 21.16 4.77	80.9	68.1	80.6	5.06	4.78	3.37

and L. cyclotis

MNHN.ZM.AC.1950-728

with 83.3°). The variation is also found at the intra-specific level in L. cyclotis. The same can be said concerning the angle between the anterior and lateral canals.

The variability is less pronounced in Elephas (from 67.9° to 74.2°) than in Loxodonta (from Loxodonta sp. MNHN.ZM.AC.2008-71 with 59.8° to L. cyclotis MNHN.ZM.AC.1957-465 with 80°).

Table II . 4 :

 II4 Measurements of the bony cochlea of extant elephants

	The number of turns of the cochlea
	is not a fully constant feature in extant
	elephants. It varies slightly in Elephas:
	MNHN.ZM.AC.2008-81, 1904-273 and
	1941-209 display 2.375 turns (855°) but
	CEB 150009 displays a little less (2.25
	turns; 810°). There is more variation in
	Loxodonta. The greatest number of turns Specimen is 2.625 (L. cyclotis: MNHN.ZM.AC.1956-	Number of turns	Coiling (°)	Length (mm)	Aspect ratio
	Elephas 1904-273	2.375		74.13	0.38
	Elephas 1941-209	2.375		80.46	0.38
	Elephas 2008-81	2.375		80.28	0.43
	Elephas CEB 150009	2.25		73.11	0.36
	Loxodonta sp 1932-523	2.25		77.13	0.41
	Loxodonta sp 2008-71 (average)	1.81		67.92	0.32
	Left ear	2		73.61	0.34
	Right ear	1.625		62.18	0.30
	Loxodonta africana 1861-53	2.375		71.54	0.45
	Loxodonta africana CEB130168	2		70.84	0.37
	Loxodonta cyclotis 1950-728	2.25		69.16	0.40
	Loxodonta cyclotis 1956-194	2.625		74.16	0.40
	Loxodonta cyclotis 1957-465	2.625		79.03	0.44
	Loxodonta cyclotis 1961-69	2.625		81.55	0.44

Table III .

 III

	Volume	Cochlea	Crus

1 : Measurements of the bony labyrinth in fossil proboscideans and outgroups. ASC: anterior semicircular canal, LSC: lateral semicircular canal, PSC: posterior semicircular canal, SCC: semicircular canals, ?: missing data, e: estimated.

commune Angles between the SCC Bony labyrinth volume (mm 3 ) Cochlea volume(mm 3 ) Relative volume of the cochlea (%) Stapedial ratio Number of turns of the cochlea Aspect ratio of the cochlea Length of the cochlea (mm) Crus commune length (mm) Crus commune average section radius (mm) Crus commune average thickness ratio Angle between the ASC and the PSC (°) Angle between the ASC and the LSC (°) Angle between the LSC and the PSC (°)

	Gomphotherium
	angustidens CBar coll. V2	988.3	497.0	50	1.5	2.63	0.47	90.1	8.73	1.24	14.2	79.2	67.8	85.3
	Gomphotherium angustidens SEP38	814.4	400.2	49	1.5	2.38	0.47	69.3	6.82	1.27	18.7	85.7	72.8	91.1
	Mammut
	americanum	936.3	343.1	37e	?	2.38	0.44	68.0	7.74	1.18	15.2	86.5	68.8	81.4
	FM14293A
	Mammut
	americanum	?	?	?	?	?	?	?	7.21	1.55	21.6	80.5	65.1	80.9
	FM14293B
	Mammuthus
	columbi	?	?	?	?	?	?	?	5.23	1.41	27	76.6	73.3	87.2
	FM144658
	Mammuthus
	primigenius	1131	480.1	42	?	2.25	0.46	67.6	5.57	1.42	25.5	68.6	71.4	88.0
	MNHN.F.1904-12
	Moeritherium 68436	?	?	?	?	1.5e	?	?	?	?	?	?	?	?
	Numidotherium koholense UOK5	84.4	35.1	42	?	1.5	0.48	27.1	4.50	0.67	14.9	78.0	75.5	96.1
	Palaeoloxodon antiquus M82706	?	?	?	?	?	?	?	6.35	1.41	22.2	77.1	76.2	92.6
	Platybelodon
	grangeri	854.5	373.8	44	?	2	0.41	56.8	4.20	1.17	27.9	73.9	67.4	98.8
	26564 (824+)
	Prodeinotherium
	Ocepeia daouiensis 2013.01108E PM45 bavaricum	17.5 674.4	11.7 322.1	66 48e	2.05 ?	2.13 2.25	0.72 0.29	19.2 ?	1.75 5.91	0.30 1.26	17.4 21.4	91.6 77.2	80.1 67.6	87.8 90.7
	Embrithopoda Stegodon PM53 orientalis	? 1117.5	? 507.8	? 45	? ?	? 2	? 0.50	? 68.7	3.92 5.34	0.53 1.37	13.7 25.7	86.0 108	83.4 74.9	98.6 94.0
	Unknown FM18632
	rhinocerotid 2013.01108A Stegomastodon sp FM21807	401.3 ?	229.2 530	57 ?	? ?	2 2	0.33 0.45	50.6 65.8	4.02 6.67	1.12 1.29	27.8 19.4	94.4 96.6	76.1 ?	98.9 ?
	Unknown
	rhinocerotid	?	?	?	?	?	?	?	4.33	1.08	24.9	91.0	73.9	95.0
	Beon 98 E1 3049
	Anancus
	arvernensis	934.6	468.3	50	1.7	2.5	0.43	72.3	5.11	1.06	20.8	90.5	58.2	77.6
	NMNHS.FM2991A
	Anancus
	arvernensis	?	?	?	?	?	?	?	6.70	1.34	20.1	81.0	58.9	78.0
	NMNHS.FM2991B
	Anancus
	arvernensis	957.5e	442.2e	46e	1.6	2.5	0.41	?	3.28	1.32	40.4	79.8	63.8	81.3
	NMNHS.FM2991C
	Anancus
	arvernensis	1151e	539.3e	47e	1.7	2.5	0.37	78e	4.58	1.64	35.8	92.4	70.4	81.2
	NMNHS.FM2991D
	Anancus
	arvernensis	1440.5	701.8	49	1.6	2.5	0.37	80.1	6.39	1.38	21.7	87.5	70.4	87.9
	NMNHS.FM2991E
	Anancus
	arvernensis	1215e	502.1e	41e	1.8	2.5	0.47	78e	7.23	1.33	18.4	88.6	68.9	80.5
	NMNHS.FM2991F
	Anancus
	arvernensis	933.9e	394.1e	42e	1.6	>2.5	0.45	73e	6.04	1.23	20.3	78.5	64.6	79.7
	NMNHS.FM2991G
	Cuvieronius sp
	FM103247	?	?	?	?	?	?	?	9.52	1.65	17.4	82.1	77.4	85.5
						127

III -Anatomy of the ear region of fossil proboscideans

Table III . 2 :

 III2 Measurements of the semicircular canals in fossil proboscideans and outgroups

	Numidotherium koholense UOK5	3.52	3.28	2.56	13.9	14.7	13.9	0.34	0.30	0.28	2.47	2.03	1.99	2.16
	Palaeoloxodon M82706 antiquus	5.87	Radius of curvature 5.14	3.93	Length (mm) 26.2 22.2 24.1	Average section radius (mm) 0.92 0.93 0.91	Average thickness ratio 3.51 4.18 3.78 3.82
	Platybelodon grangeri 26564 Prodeinotherium bavaricum 2013.01108E Stegodon orientalis FM18632 Ocepeia daouiensis Stegomastodon sp FM21807	ASC 5.16 5.60 5.36 1.64 4.91	PSC 4.89 5.01 7.48 1.55 5.30	LSC 3.54 3.98 3.27 1.24 ?	ASC 22.0 24.7 23.7 6.87 19.4	PSC 22.0 22.5 23.4 7.49 22.5	LSC 22 22.7 15.2 6.79 ?	ASC 0.81 0.69 0.83 0.15 1.32	PSC 0.65 0.69 0.82 0.16 1.18	LSC 0.68 0.59 0.77 0.14 ?	ASC 3.69 2.79 3.51 2.22 6.8	PSC 2.93 3.06 3.51 2.18 5.24	LSC 3.11 2.62 5.10 2.04 ?	3.25 2.82 4.04 Global thickness ratio 2.15 6.02
	Unnamed Embrithopoda	3.26	3.13	2.3e	12.6	13.4	11e	0.22	0.21	0.12	1.72	1.57	1.1e	1.46
	Rhinocerotid 2013.01108A	4.13	3.98	3.44	17.4	19.2	18.5	0.42	0.45	0.44	2.39	2.36	2.37	2.37
	Rhinocerotid Beon 98 E1 3049	4.19	3.94	3.26	17.5	18.6	17.4	0.54	0.51	0.64	3.09	2.76	3.66	3.17
	Anancus arvernensis NMNHS.FM2991A	5.02	4.79	3.19	22.7	20.9	20.3	0.70	0.70	0.74	3.09	3.37	3.63	3.36
	Anancus arvernensis NMNHS.FM2991B	5.91	5.63	4.06	25.4	23.9	24.4	0.58	0.64	0.66	2.29	2.66	2.72	2.56
	Anancus arvernensis NMNHS.FM2991C	5.15	4.89	3.39	23.8	21.5	21.7	0.76	0.74	0.78	3.18	3.43	3.58	3.40
	Anancus arvernensis NMNHS.FM2991D	5.24	5.39	3.39	23.5	24.1	21.7	0.79	0.82	0.84	3.36	3.40	3.86	3.54
	Anancus arvernensis NMNHS.FM2991E	5.52	5.37	3.54	24.3	23.0	21.8	0.91	0.92	1.06	3.75	3.99	4.87	4.20
	Anancus arvernensis NMNHS.FM2991F	5.68	5.67	3.92	24.6	25	23.6	0.83	0.78	0.83	3.39	3.10	3.50	3.33
	Anancus arvernensis NMNHS.FM2991G	5.33	5.67	3.58	23.2	25.8	22.2	0.79	0.70	0.79	3.39	2.70	3.56	3.21
	Cuvieronius sp FM103247	6.18	6.06	3.57	25.0	25.4	21.4	0.85	0.86	0.89	3.41	3.37	4.18	3.65
	Gomphotherium
	angustidens	5.26	5.56	3.71	20.4	23.2	22.2	0.77	0.76	0.78	3.78	3.26	3.50	3.51
	CBar coll. V2
	Gomphotherium angustidens SEP38	5.45	5.11	3.36	22.8	21.6	19.1	0.64	0.71	0.78	2.82	3.29	4.09	3.40
	Mammut
	americanum	6.33	6.09	3.82	28.8	25.5	24.1	0.95	0.95	0.92	3.30	3.70	3.82	3.61
	FM14293A
	Mammut
	americanum	5.43	5.68	2.96	23.6	23.8	18.4	1.01	1.04	0.87	4.30	4.33	4.74	4.47
	FM14293B
	Mammuthus columbi FM144658	5.71	4.84	3.08	25.9	21.2	21.3	1.10	1.2	0.99	4.24	5.65	4.65	4.85
		5.80	5.53	2.92	26.8	25.3	19.7	0.88	1.01	0.93	3.28	3.99	4.69	3.99
						129

Mammuthus primigenius MNHN.F.1904-12

III -Anatomy of the ear region of fossil proboscideans

Table III . 3 :

 III3 Angle between the cerebral and cerebellar surfaces and stapedial ratio of Anancus arvernensis. "?" is for missing data.

		III -Anatomy of the ear region of fossil proboscideans
	The subarcuate fossa is absent, however
	the cerebellar surface of the petrosal is
	slightly	convex	except	for
	NMNHS.FM2991B in which it is completely
	flat. The internal auditory meatus is
	oriented antero-posteriorly as in extant
	elephants. The crista partis petrosa is
	blunt in general but it is sharper in
	specimens NMNHS.FM2991C, F and G. In
	cerebral view, the middle meningeal
	artery leaves a deep groove on the surface
	of the tegmen tympani. This feature is
	visible in every specimen except for
	NMNHS.FM2991E, F and G in which the
	tegmen tympani is broken.
		In tympanic view, the unique
	perilymphatic foramen is retained during
	ontogeny, therefore, the cochlear
	canaliculus is absent. The promontorium is
	bulbous and exhibits a very thick crista
	interfenestralis. The fenestra vestibuli is
	oval. Its stapedial ratio varies around 1.7
	(Table III.3). A lateral protuberance (like in	Angle between	Stapedial ratio
	some extant elephants specimens) is	surfaces
	present near the perilymphatic foramen in	NMNHS.FM2991A	110°	1.7
	several specimens (NMNHS.FM2991A, B, C	NMNHS.FM2991B	100°	?
	and G). The fragile mastoid process is	NMNHS.FM2991C	95°	1.6
	broken in all of the studied specimens.	NMNHS.FM2991D	100°	1.7
					NMNHS.FM2991E	90°	1.6
					NMNHS.FM2991F	90°	1.8
					NMNHS.FM2991G	100°	1.6

  -Anatomy of the ear region of fossil proboscideans

	average except for NMNHS.FM2991B and	almost	right	values	(87.9°	in
	NMNHS.FM2991E which have respectively	NMNHS.FM2991E). It is the same for the
	very low (0.66 mm) and high (1.06 mm)	angle between the anterior and posterior
	values. Hence NMNHS.FM2991B has a	canals	(between	78.5°		in
	particularly low posterior thickness ratio	NMNHS.FM2991G	and	92.40		in
	compared to the other specimens (2.72)	NMNHS.FM2991D). In some specimens,
	although this is less marked than for its	the largest angle is the one between the
	anterior canal (2.25). The relative	anterior	and	posterior	canals
	slenderness of the lateral canal of this	(NMNHS.FM2991A,	NMNHS.FM2991B,
	specimen is distinct on the reconstruction.	NMNHS.FM2991D and NMNHS.FM2991F)
	In contrast NMNHS.FM2991E has a	while it is the opposite in others
	particularly high lateral thickness ratio	(NMNHS.FM2991C, NMNHS.FM2991E and
	(4.87). Other specimens have more or less	NMNHS.FM2991G). If we compare the
	similar thickness ratio values (3.50 to	radii of curvature we can observe that the
	3.86). The average lateral thickness ratio	lateral canal is always smaller than the
	of all seven specimens of Anancus is 3.67	anterior and posterior canals, which tend
	(which is slightly higher than the two other	to share more similar radii of curvature
	canals). The radius of curvature of the	(see Table III.2). However, the radius of
	anterior canal is 3.58 on average. This	curvature of the anterior canal is always
	value varies from 3.19 (NMNHS.FM2991A)	larger than for the posterior canal, except
	to 4.06 (NMNHS.FM2991B).	for	NMNHS.FM2991D		and
	The angle between the anterior	NMNHS.FM2991G. The anterior canal
	and lateral canals is always the lowest in	apex is located higher than the posterior
	Anancus specimens. It is always acute and	canal apex. In NMNHS.FM2991G, this
	varies from particularly low values (58.20°	feature is present but less marked. In
	and 58.9° in NMNHS.FM2991A and	Anancus, the thickness of the canals is
	NMNHS.FM2991B respectively) to higher	average compared to other proboscideans
	values (70.4° in NMNHS.FM2991D and

NMNHS.FM2991E). The angle between the lateral and posterior canals oscillates between acute values (the lowest angle being 77.6° in NMNHS.FM2991A) and

Table III . 2

 III2

			III -Anatomy of the ear region of fossil proboscideans
	The variance is smaller in Elephas
	maximus (0.35) and even smaller in
	Anancus specimens (0.24). However, such
	values are to be taken with caution
	because of our very small sample.
	III.42. Early proboscideans tend to display Concerning the outgroups, the earliest
	more slender semicircular canals than known afrotherian Ocepeia daouiensis
	modern exhibits a small ratio (therefore slender proboscideans. Eritherium
	exhibits the most slender semicircular semicircular canals) which is close to the
	canals (ratio of 1.08). Phosphatherium and ratios of Numidotherium and
	Numidotherium canals are slightly thicker Phosphatherium (2.15). The early sirenian
	(respectively 2.24 and 2.16) but still from Chambi displays slender canals as
	relatively slender compared to modern well (2.18). In embrithopods, the
	proboscideans. The value is not available unpublished early specimen has very thin
	for Moeritherium. The specimen referred canals (1.46) while Arsinoitherium displays
	to Prodeinotherium exhibits thicker canals canals as thick as modern elephants
	(2.82) but they are still less thick than (3.42). Elephantulus is in the middle range
	modern proboscideans. Elephantimorphs (2.79). This character seems interesting to
	always display ratios over 3.00 and up to keep for our phylogenetic analysis. Placing
	4.86 with one exception being a specimen the states limit at 3 seems to discriminate
	well	early	proboscideans	from
	elephantimorphs. Moreover, except for
	one Loxodonta specimen that displays a
	ratio of 3.02 (MNHN.AC.ZM.1932-523),
	there is a considerable gap in the
	distributions of the ratio between values
	under 2.82 and values over 3.21.

(beginning of chapter III). The distribution of the global thickness ratio of the semicircular canals is given in Fig.

of

Loxodonta (MNHN.AC.ZM.1956-194)

with a ratio of 2.74. It appears that the semicircular canals of proboscideans are primitively slender. They tend to become progressively thicker in modern taxa. The group that includes the most recent common ancestor of Prodeinotherium and elephantimorphs contains only taxa with a ratio over 2.7. Some extant specimens display ratios up to 4.86 (ElephasMemb). There is some intraspecific variability among Anancus, Loxodonta and Elephas specimens. The Loxodonta specimens display the greater variance (0.40) but the specimens compared are not all from the same species. Within Loxodonta cyclotis specimens, the variance is even greater (0.70).

Figure III.42 : Distribution of the global thickness ratio of the semicircular canals among proboscideans and some outgroups. Values are summarized in Appendix 15.

Table IV . 2 :

 IV2 Relative participation of the principal components (PCs) in the different analyses (in % of the total variation)

		PC1	PC2	PC3	PC4	PC5	PC6
	Afrotheria -Whole labyrinth (A1)	31.8	23.5	12.5	9.2	5	3.7
	Afrotheria -Canals only (A2)	40.6	15.5	8.5	6.2	5.3	4.7
	Proboscidea -Whole labyrinth (P1)	36.6	19.8	11	8.3	5.8	3.9
	Proboscidea -Canals only (P2)	32.4	15.4	9.9	9.5	6.3	4.5
	Extant elephants -Whole labyrinth (E1)	52.2	14.8	12	6.7	4.1	2.9
	Extant elephants -Canals only (E2)	36.2	17.1	12.8	10.5	6.6	5.4

Table IV . 3 :

 IV3 Results of the phylogenetic generalized least-squared regressions performed on the first three PCs of analyses A1 (whole labyrinth of Afrotheria), A2 (semicircular canals of Afrotheria), P1 (whole labyrinth of Proboscidea) and P2 (semicircular canals of Proboscidea). Bold p-values are for principal components significantly influenced by the size.

			p-value	Adjusted R-square
		PC1	0.6429	-0.05858
	A1	PC2 0.03247	0.2525
		PC3 0.01584	0.3232
		PC1 0.001288	0.3823
	A2	PC2	0.637	-0.03808
		PC3	0.3785	-0.009078
		PC1	0.6636	-0.09704
	P1	PC2 2.74E-06	0.9371
		PC3 0.01549	0.4824
		PC1 0.005409	0.4191
	P2	PC2 7.14E-05	0.6932
		PC3 0.03208	0.2538

Table VI .2 : Raw functional parameters of extant afrotherians. Elephantulus Elephas Procavia Short time constant (T 2 ) of the anterior duct, in ms

 VI

	1.2	14.2	1.9
	Short

time constant (T 2 ) of the posterior duct, in ms

	1.2	11.8	2.1
	Short

time constant (T 2 ) of the lateral duct, in ms

	1.3	8.6	2.0
	Natural

frequency (ω 0 ) of the anterior duct, in Hz

	4.3	0.7	2.4
	Natural

frequency (ω 0 ) of the posterior duct, in Hz

	5.7	0.9	2.4
	Natural

frequency (ω 0 ) of the lateral duct, in Hz

	4.3	0.7	3.2
	Sensitivity (

velocity gain VGs) of the anterior duct, in mdeg/deg.s -1

	0.0036	0.0339	0.0058
	Sensitivity (

velocity gain VGs) of the posterior duct, in mdeg/deg.s -1

	0.0037	0.0393	0.0060
	Sensitivity (

velocity gain VGs) of the lateral duct, in mdeg/deg.s -1

	VI -The semicircular duct system of the Proboscidea and the Afrotheria
	This means that responses within head angular rotation Elephas is able to	Natural frequency (ω 0 )
	the semicircular duct system are detect is ten times smaller than in
	approximately 1.5 times faster in Elephantulus and six times smaller than in	Elephas exhibits particularly low
	Elephantulus than in Procavia. In contrast, Procavia. This also means that the	values for the natural frequency. This
	Elephas exhibits extremely high short-time maximal angular velocities that Elephas is	implies that elephants do not tend to
	constants. Its vertical short-time constants able to experiment in pitch and roll are	display high frequency motion of the
	are more than ten times higher than in ten times less important than in	head. The values are similar in all three
	Elephantulus while its lateral short-time Elephantulus and six times less important	semicircular ducts, hence this tendency is
	constant is almost eight times higher than than in Procavia. Regarding the lateral	constant in pitch, roll and yaw motion.
	in Elephantulus. This implies that the duct, the difference is less marked with	Elephantulus, on the other hand, displays
	vestibular system of Elephas responds to Elephas exhibiting a sensitivity four times	higher values of the natural frequency
	angular rotations much more slowly than higher than Elephantulus and two times	which means it is capable to move its head
	in Elephantulus and Procavia. This is higher than Procavia.	more often. The value is even higher for
	probably due to the particularly large size To better compare vertical and	the posterior duct, meaning that
	and body mass of Elephas but this does lateral values of the sensitivity within the	Elephantulus is capable of particularly
	not change the fact that the vestibular same individual, an ideal inclination of the	frequent head motion along pitch and/or
	system of Elephas is slower to respond to vertical ducts with the coronal plane (45°)	roll axes. Procavia displays somewhat
	the excitation than the two other studied has to be taken into account. Hence the	average values compared to the other two
	afrotherians. On the other hand, Elephas values for the vertical ducts have to be	afrotherians. However, given its higher
	also displays significant differences multiplied by 0.707 (cos(45°)). A ratio of	natural frequency in the lateral duct, it is
	between values of vertical and lateral vertical/lateral values (that we will call the	capable of higher frequency motion in yaw
	ducts. Vertical ducts (and especially the V/L ratio in this work) is calculated to	than in pitch and roll.
	anterior duct) display higher short-time express differences between lateral and
	constants and therefore respond more vertical values and is given in Table VI.3.	Sensitivity (or velocity gain, VGs)
	slowly to angular rotations than the lateral	Elephas displays the highest
	duct. This means that elephants are The equation to calculate the V/L ratio is:	sensitivity values of the three studied
	capable to respond more rapidly to yaw	afrotherians. The sensitivity of its vertical
	motion than to pitch or roll motion.	ducts is approximately ten times higher
		0.0030	0.0123	0.0055
	Sensitivity V/L ratio	0.85	2.10	0.76

than in Elephantulus and approximately six times higher than in Procavia. This means that the minimal change in vertical

Table VI . 3 :

 VI3 Body mass-free functional parameters of the semicircular duct system of afrotherians

					Elephantulus	Elephas	Procavia	Mammalian ancestral	morphotype
	Short time constant (T 2 ) of the anterior duct, in ms	4.2	6.4	3.1	3.7
	Short time constant (T 2 ) of the posterior duct, in ms	4.6	5.0	3.5	4.0
	Short time constant (T 2 ) of the lateral duct, in ms	4.7	3.9	3.2	3.1
	Natural frequency (ω 0 ) of the anterior duct, in Hz	1.9	1.5	1.7	1.4
	Natural frequency (ω 0 ) of the posterior duct, in Hz	2.4	1.6	1.8	1.7
	Natural frequency (ω 0 ) of the lateral duct, in Hz	2.0	1.1	2.4	1.7
	Sensitivity (velocity gain VGs) of the anterior duct, in mdeg/deg.s -1	0.0157 0.0132 0.0101 0.0098
	Sensitivity (velocity gain VGs) of the posterior duct, in mdeg/deg.s -1	0.0175 0.0145 0.0109 0.0095
	Sensitivity (velocity gain VGs) of the lateral duct, in mdeg/deg.s -1	0.0133 0.0048 0.0096 0.0075
	Sensitivity V/L ratio		0.88	2.04	0.77	0.91
		The short time constants of
	Procavia are similar between ducts. At
	equal body mass, they are slightly lower
	than	the	mammalian	ancestral
	morphotype for the vertical ducts and

Table VII . 1 :

 VII1 Afrotherian taxa segmented during the thesis for which at least one labyrinth preserves the cochlea. The first number refers to the number of specimens and the number in bracket refers to the number of labyrinths. Numbers in italics are for incomplete labyrinths.

	Genus	Species	Specimens (ears)
	Ocepeia	daouiensis	1(2)
	Eritherium	azzouzorum	1(1)
	Phosphatherium	escuilliei	1(2)
	Numidotherium	koholense	1(1)
	Moeritherium	lyonsi	1(1)
	Prodeinotherium	bavaricum	1(1)
	Mammut	americanum	1(1)
	Platybelodon	grangeri	1(1)
	Gomphotherium	angustidens	2(3)
	Stegomastodon	sp.	1(1)
	Stegodon	orientalis	1(2)
	Anancus	arvernensis	6(6)
	Loxodonta	sp.	2(3)
	Loxodonta	africana	2(2)
	Loxodonta	cyclotis	4(4)
	Mammuthus	primigenius	1(1)
	Elephas	maximus	4(4)

  Appendix 11 -Comparisons of the stapedial ratio values in proboscideans and other mammals

		Stapedial	MNHN.AC.ZM.1950-278
		ratio	Loxodonta cyclotis	1.74
	Amphiorycteropus (Benoit et al.,	1.18	MNHN.AC.ZM.1957-465
	2015; average)		Loxodonta cyclotis	1.69
	Anancus NMNHS.FM2991A	1.66	MNHN.AC.ZM.1961-69
	Anancus NMNHS.FM2991C	1.64	Loxodonta sp	1.72
	Anancus NMNHS.FM2991D	1.73	MNHN.AC.ZM.1932-523
	Anancus NMNHS.FM2991E	1.65	Loxodonta sp	1.65
	Anancus NMNHS.FM2991F	1.76	MNHN.AC.ZM.2008-71 (left)
	Anancus NMNHS.FM2991G	1.58	Loxodonta sp	1.74
	Arsinoitherium BMNH 8800	1.60	MNHN.AC.ZM.2008-71 (right)
	Chambi sirenian	1.95	Macroscelides (Benoit et al.,	1.78
	Chambius (Benoit et al., 2013c)	1.72	2013)
	Chrysochloris (Benoit et al.,	2.26	Macroscelides (Ekdale, 2013)	1.90
	2015; average)		Numidotherium unlabeled	1.81
	Chrysochloris (Ekdale, 2013)	2.80	(Benoit et al., 2013b)
	Dendrohyrax (Benoit, 2013)	2.07	Orycteropus (Benoit et al., 2015;	1.80
	Elephantimorpha (Ekdale, 2011)	1.60	average)
	Elephantulus (Benoit, 2013)	1.65	Petrodromus (Benoit, 2013)	1.50
	Elephas CEB150009	1.52	Phosphatherium PM17	1.62
	Elephas MNHN.AC.ZM.1904-273	1.83	Plesiorycteropus (Benoit et al.,	1.42
	Elephas MNHN.AC.ZM.1941-209	1.65	2015; average)
	Elephas MNHN.AC.ZM.2008-81	1.63	Potamogale (Benoit et al., 2015;	1.61
	Eritherium PM88	1.57	average)
	Gomphotherium Cbar coll. V2	1.52
	Gomphotherium MNHN.F.SEP38	1.48
	Helioseus (Benoit, 2013)	1.55
	Hemicentetes (Ekdale, 2013)	1.60
	Heterohyrax (Benoit, 2013)	1.74
	Hyopsodus (Ravel & Orliac,	1.44
	2015)
	Kulbeckia (Ekdale, 2013)	2.00
	Loxodonta africana CEB130168	1.70
	Loxodonta africana	1.58
	MNHN.AC.ZM.1861-53
	Loxodonta cyclotis	1.76

  Appendix 16 -Comparisons of the number of turns of the cochlea in mammals

	other mammals (page 1/3) other mammals (page 2/3) other mammals (page 3/3)		Turns
	Anterior radius of curvature 3.26 5.01 5.91 5.15 Anterior radius of curvature 1.1 4.43 1.48 Anterior radius of curvature Amphiorycteropus (Benoit et al., Amphiorycteropus (Benoit et al., 2015) Anancus NMNHS.FM2991A Anancus NMNHS.FM2991B Anancus NMNHS.FM2991C Hemicentetes (Benoit et al., 2015) Heterohyrax (Benoit, 2013) Hyopsodus (Ravel & Orliac, 2015) 1.714 Posterior radius of curvature 2.83 4.79 5.63 4.89 Posterior radius of curvature 0.89 4.11 1.19 Posterior radius of curvature 2015) Anancus NMNHS.FM2991A 2.500 Platybelodon 26564 (824+) 5.37 4.81 Anancus NMNHS.FM2991C 2.500 Plesiorycteropus (Benoit et 2.31 1.89 Anancus NMNHS.FM2991D 2.500 al., 2015) Anancus NMNHS.FM2991E 2.500 Potamogale (Benoit et al., 2015) 1.61 1.37 Anancus NMNHS.FM2991F 2.500 Anancus NMNHS.FM2991D 5.24 5.39 Anancus NMNHS.FM2991E 5.52 5.37 Anancus NMNHS.FM2991F 5.68 5.67 Anancus NMNHS.FM2991G 5.21 5.69 Arsinoitherium BMNH 8800 4.5 4.34 Chambius (Benoit et al., Chrysochloris (Benoit et al., Chrysochloris (Benoit et al., Cuvieronius FM103247 6.18 6.06 2013) 2.3 2.38 Didelphis (Ekdale, 2013) 1.46 1.23 Dugong (Benoit et al., 2013b) 2.85 2.57 Elephantimorph (Ekdale, 2011) 5 5.5 Elephantulus (Benoit et al., 2013c) 1.4 1.24 Elephas CEB150009 5.04 4.65 MNHN.AC.ZM.1904-273 5.23 5.2 MNHN.AC.ZM.1941-209 5.27 5.21 MNHN.AC.ZM.2008-81 4.97 5.64 Embrithopoda PM53 3.26 3.13 Eritherium PM88 1.74 1.83 V2 5.25 5.99 Helioseus (Benoit, 2013) 1.42 1.27 2013) 1.52 1.23 Petrodromus (Benoit, MNHN.F.SEP38 5.45 5.12 Palaeoloxodon M82706 5.87 5.14 Gomphotherium 2015) 3.37 3.14 Orycteropus (Benoit et al., Gomphotherium Cbar coll. Ocepeia PM45 1.64 1.55 Numidotherium UOK5 3.7 3.29 (Benoit et al., 2013b) 3.27 3.21 Numidotherium unlabelled Elephas MNHN.F.1904-12 5.8 5.52 Mammuthus primigenius Elephas FM144658 (right) 5.68 4.81 Mammuthus columbi Elephas MNHN.AC.ZM.2008-71 5.17 5.13 Mammut FM14293A 6.33 6.09 5.63 5.62 Mammuthus columbi FM144658 (left) 5.71 4.84 2013) 1.46 1.2 Zalambdalestes (Ekdale, Mammut FM14293B MHNT.PAL.2013.01108A 4.13 3.98 Unknown rhinocerotid al., 2013c) 1.27 1.08 Unknown rhinocerotid 4.19 3.94 Macroscelides (Benoit et 2013c) 4.3 4.46 Trichechus (Benoit et al., Loxodonta sp Loxodonta sp Titanohyrax (Benoit, 2013) 2.42 2.34 MNHN.AC.ZM.1932-523 5.65 5.35 1.19 1.11 Tenrec (Benoit et al., 2015) Dendrohyrax (Benoit, Loxodonta cyclotis MNHN.AC.ZM.1961-69 5.08 4.8 5.36 7.48 Stegodon FM18632 Sirenian from Chambi 2.21 2.14 2015) 0.98 0.68 Loxodonta cyclotis MNHN.AC.ZM.1957-465 5.46 4.96 2016) 1.52 1.54 Seggeurius (Benoit et al., 2015) 0.86 0.68 Loxodonta cyclotis MNHN.AC.ZM.1956-194 6.86 6.25 2013) 2 1.77 Rhynchocyon (Benoit, 2013c) 0.8 0.71 Loxodonta cyclotis MNHN.AC.ZM.1950-278 5.37 4.91 O'Leary, 2016) 1.18 1.02 Protungulatum (Orliac & Kulbeckia (Ekdale, 2013) 1.19 0.96 Loxodonta africana CEB130168 5.8 5.56 Loxodonta africana MNHN.AC.ZM.1861-53 6.1 5.2 Prorastomus 2.84 3.01 MHNT.PAL.2013.01108E 5.6 5.01 Prodeinotherium 2013b) 2.12 1.66 Procavia (Benoit et al., Arsinoitherium BMNH 8800	2015; Trichechus (Ekdale, 2013) average) Zalambdalestes (Ekdale, 2013) Mean radius of the vertical canals Lateral radius of curvature 3.05 3.3 4.9 3.19 5.77 4.06 5.02 3.39 Mean radius of the vertical canals Lateral radius of curvature Lateral canal 1.45 1.60 1.70 Lateral canal ratio (%) 108.4 65 70.4 ratio (%) 1 0.68 68.3 4.27 3.39 79.4 1.34 1.12 83.9 Mean radius of the vertical canals Lateral radius of Lateral canal ratio (%) curvature 5.09 3.55 69.7 2.1 2.14 101.9 1.49 1.49 100 67.6 5.32 3.43 64.5 5.45 3.54 65.1 5.68 3.92 69.1 5.45 3.64 66.8 4.42 3.3 6.12 3.58 58.5 2.34 1.97 84.2 1.35 0.88 2.71 2.41 88.9 5.25 2.7 51.4 1.32 1.05 79.5 4.85 3.65 75.3 5.22 3.16 60.5 5.24 3.52 67.1 5.31 4.06 76.5 3.2 2.29 1.78 1.38 5.62 3.71 66 1.35 1.24 92.2 1.38 1.32 96 5.28 3.36 63.7 5.51 3.99 72.4 3.26 3.42 105.1 1.59 1.25 78.5 77.5 3.49 2.56 73.3 71.7 3.24 2.46 75.9 5.66 2.92 51.6 5.24 3.24 61.8 5.15 3.56 69.2 6.21 3.84 61.8 5.62 2.96 52.7 5.28 3.08 58.4 1.33 1.21 91 4.06 3.44 84.9 1.18 1.02 86.8 4.06 3.26 80.3 4.38 3.54 80.8 65.4 2.38 2.15 90.3 5.5 3.21 58.3 1.15 1.12 97.4 4.94 3.37 6.42 3.27 51 68.3 2.18 1.95 89.6 0.83 0.66 79.5 5.21 3.17 60.8 1.53 1.28 83.7 0.77 0.61 79.2 6.55 4.09 62.3 1.89 1.45 76.9 0.76 0.65 86.1 5.14 3.35 65.1 1.1 0.94 85.5 74.7 1.08 0.92 85.6 5.68 3.72 5.65 3.54 2.93 2.96 101.2 62.7 5.31 3.98 75 65.4 1.89 1.97 104.2
	Phosphatherium PM17	1.91	1.88	1.9	1.49	78.5

  .844

	Elephantulus MNHN.AC.ZM.1930-92	1.875
	Elephas CEB150009	2.250
	Elephas MNHN.AC.ZM.1904-273	2.375
	Elephas MNHN.AC.ZM.1941-209	2.375
	Elephas MNHN.AC.ZM.2008-81	2.375
	Eritherium PM88	2.000
	Gomphotherium Cbar coll. V2	2.625
	Gomphotherium MNHN.F.SEP38	2.375
	Helioseus

La région de l'oreille osseuse chez les Proboscidea (Afrotheria, Mammalia) : anatomie, fonction, évolution Résumé Les

  éléphants font partie des rares mammifères capables d'entendre les infrasons et leur comportement locomoteur est unique. Ces singularités correspondent à des spécialisations de leurs organes sensoriels contenus dans l'oreille interne : la cochlée (audition) et le système vestibulaire (locomotion). Alors que la diversité actuelle des proboscidiens est très faible (trois espèces), ce groupe a été bien plus diversifié pendant les 60 millions d'années qui composent son histoire. Cette thèse étudie pour la première fois de façon complète la morphologie et la fonction de la région de l'oreille (périotique, labyrinthes osseux et membraneux) d'éléphants actuels grâce aux techniques CT scan 3D. De plus, les périotiques de quatorze genres de proboscidiens fossiles sont décrits afin de documenter l'évolution de ce complexe anatomique au sein de cet ordre de mammifères. Les résultats montrent que certains caractères de l'oreille sont très variables au niveau spécifique. Notre analyse inclut les plus anciens proboscidiens connus et suggère que la morphologie de la région otique a évolué graduellement pendant la première moitié de l'histoire évolutive du groupe et que le morphotype moderne éléphantin est déjà acquis chez les Deinotheriidae et généralisé chez les éléphantimorphes. Les inférences sur la locomotion et l'audition des taxons fossiles confirment ces observations. Ce travail permet ainsi de lever le voile sur l'évolution d'une région anatomique majeure, jusque-là méconnue chez un groupe emblématique de mammifères.

		.428
	Procavia CEB150012	3.500
	Prodeinotherium MHNT.PAL.2013.01108E	2.250
	Prorastomus (Benoit et al., 2013a)	1.530
	Rhynchocyon (Benoit, 2013)	2.119
	Seggeurius (Benoit et al., 2016)	1.910
	Sirenian from Chambi (Benoit et al., 2013a)	2.500
	Stegodon FM18632	2.000
	Stegomastodon FM21807	2.000
	Tenrec (Benoit et al., 2015)	1.767
	Tenrec MNHN.AC.ZM.1933-3	1.875
	Titanohyrax (Benoit, 2013)	1.919
	Trichechus (Benoit et al., 2013b)	1.131
	Unknown rhinocerotid MHNT.PAL.2013.01108A	2.000
	Zalambdalestes (Ekdake, 2012)	1.022

Mots clés : périotique, labyrinthe, Proboscidea, éléphant, anatomie, phylogénie, analyse fonctionnelle

in tympanic (A), medial (B), cerebellar (C) and cerebral (D) views. Legends: a.v. aquaeductus vestibuli, c.i. crista interfenestralis, c.p.p. crista partis petrosa, e.w. epitympanic wing, g.m.m.a. groove for the middle meningeal artery, i.a.m. internal auditory meatus, p.f. perilymphatic foramen, p.m. pars mastoidea, pr promontorium, s.c. stylomastoid canal, t.t. tegmen tympani, ty tympanohyal

III -Anatomy of the ear region of fossil proboscideans

[START_REF] Gheerbrant | L'origine et l'évolution des éléphants[END_REF]. It is supported by two non-

Remerciements

CHAPTER III Anatomy of the ear region of fossil proboscideans: comparisons with extant elephants and close relatives CHAPTER VII Preliminary considerations on the auditory capacities of proboscideans

CHAPTER II

Petrosal and inner ear anatomy of extant elephants

Material and methods

Taxa sample

In this chapter, we investigated the significance of the morphology at three distinct systematics levels, involving three distinct taxa samples: 1) analysis including specimens of afrotherians; 2) analysis restricted to proboscidean taxa;

3) analysis including only extant proboscideans. Although most of our specimens preserve the cochlea, there are several fossils in our taxa sample for which we do not have cochlear landmarks. In order to include these taxa in our study of the cochlea, we performed two analyses for each investigated question: one with cochlear landmarks and one without cochlear landmarks. Therefore, we conducted six different analyses:

-A1, analysis of the whole labyrinth including all afrotherian specimens preserving the cochlea; -A2, analysis restricted to the semicircular canals and therefore including all afrotherian specimens;

-P1, analysis of the whole labyrinth of all proboscidean specimens that preserve the cochlea;

-P2, analysis restricted to the semicircular canals that includes all the proboscideans ; -E1, analysis of the whole labyrinth of all extant elephants; -E2, analysis restricted to the semicircular canals of extant elephants.

The composition of each data sample is summarized in Table IV.1. to decrease but less than in A2. However, the point of entry of the lateral canal into the vestibule still tends to be located higher.

Figure IV.13 :

Deformations along the first axis of the analysis (PC1, 32.4%) restricted to the semicircular canals of Proboscidea (P2) in the view showing the plane of the anterior (A), posterior (B) and lateral (C) canals. "-" represents the extreme shape towards the negative extremity of the axis, "+" the extreme shape towards the positive extremity of the axis and "0" the mean shape on this axis.

V -Evolution of the ear region characters within the Proboscidea and the Afrotheria

Character cartography performed on the Proboscidea

Introducing characters of the ear region in the published matrices of Proboscidea (e.g. [START_REF] Delmer | Les premières phases de différenciation des proboscidiens (Tethytheria, Mammalia): le rôle du Barytherium grave de Libye[END_REF] yields a set of problems. Although the total evidence approach [START_REF] Kluge | A concern for evidence and a phylogenetic hypothesis of relationships among Epicrates (Boidae, Serpentes)[END_REF] has been widely accepted it sometimes brings undesirable ambiguities or noise (i.e. [START_REF] Lecointre | Le principe du "total evidence" requiert l'exclusion de données trompeuses[END_REF], especially when the taxonomic samples are too different in terms of both taxa and characters. On the one hand several terminal taxa used in the present analyses have not been coded in previously published analyses. On the other hand, many terminal taxa in previously published analyses do not bear ear-region information. The combination of these two difficulties can only bring the inflation of missing data (an undesirable result in respect to total evidence) unless a careful revision and recoding of all known proboscidean characters used by previous authors is done, which is beyond the scope of this study. Sometimes more is less. Hence the decision was taken to 1) compare the result of the characters of the ear region to the presently accepted phylogeny of Proboscidea, and 2) map the ear region characters on the presently accepted phylogeny of Proboscidea, so that both congruence and incongruence in distributions of characters between the two resulting analyses can be discussed and explained. The consensual tree used to map the characters is a synthesis of [START_REF] Tassy | Gaps, parsimony, and early Miocene elephantoids (Mammalia), with a reevaluation of Gomphotherium annectens (Matsumoto, 1925)[END_REF], [START_REF] Tassy | Who is who among the Proboscidea[END_REF], [START_REF] Kalb | The Proboscidea: evolution and palaeoecology of elephants and their relatives[END_REF], [START_REF] Shoshani | Para-or monophyly of the gomphotheres and their position within Proboscidea. The Proboscidea: Evolution and palaeoecology of elephants and their relatives[END_REF] and [START_REF] Shoshani | Elephantidae phylogeny: morphological versus molecular results[END_REF].

Cladistic analysis performed on the Afrotheria

Two cladistic analyses were performed on the Afrotheria, using the software TNT [START_REF] Goloboff | TNT, a free program for phylogenetic analysis[END_REF]. The analyses are based on the same 32 ear region characters used in the Proboscidea analysis. The multi-state characters were treated as ordered as well, as we consider them to be morphological clines. In the analyses extended to Afrotheria, three characters remain not informative (8, 25 and 27). Kulbeckia is defined as the outgroup. A first analysis was carried out with all the characters equally weighted and using a traditional search (10 random seeds and 100 replicates). The second analysis was carried out using implied The subarcuate fossa is fully filled in later proboscideans (node 4) which all lack a distinct subarcuate fossa on the cerebellar surface of the petrosal. In Moeritherium, both states were observed. A synapomorphic reversion appears either at node 5 or node 6.

Extension of the anterior canal apex

Finally, the extension of the anterior canal apex seems to be lost in Stegomastodon (observed in both studied specimens).

Vestibulo-cochlear angle

Axis of rotation of the apical turn of the cochlea with respect to the basal turn

The evolution of the alignment of the axis of rotation of the apical turn of the cochlea with respect to the basal turn is illustrated in Fig V .60. The axis of rotation of the apical turn is primitively aligned with the axis of rotation of the apical turn in Proboscidea. This feature is found in outgroups (Ocepeia, Protungulatum) and in early proboscideans (Eritherium, Numidotherium). In all of these taxa, the apical and basal turns are centered on the bony modiolus.

CHAPTER VI

The semicircular duct system of the Proboscidea and the Afrotheria: functional capacities and inferences on the inner ear of extinct taxa

Material and methods

Taxa sample

Three extant specimens preserving the membranous labyrinth were sampled (Procavia, Elephantulus and Elephas), in a view to segment the membranous ducts in 3D. The reconstructions are used, amongst other things, in order to infer the membranous features of extinct taxa. On the other hand, the bony labyrinths of proboscideans that were segmented during the thesis were prepared in order to infer their functional capacities. Only specimens preserving all three semicircular canals are analyzed here (Table VI.1).

Preparation of the membranous specimens

Dissection and stain protocol

The membranous labyrinth of Elephantulus was sampled on a specimen conserved in formaldehyde from the ). We used these regressions in order to compute residuals for the logarithm of each functional parameter.

We then calculated estimated values for the logarithm of the functional parameters of the three afrotherian species, as if they weighted the same mass (50 kg), to which we added the previously computed residuals, and we finally raised 10 to the power of the obtained value to get body mass-free functional parameters.

Functional parameters of an estimated mammalian ancestral morphotype, based on these 30 mammal species, are used as a comparison.

Functional inferences on the bony specimens

To infer the functional capacities of the fossil taxa, the corresponding bony

Results & discussion

Length and number of turns

As previously said, the product of the absolute cochlear length and the number of turns of the cochlea is a proxy to estimate the hearing capacities of fossil mammals. This product correlates positively with low-frequency hearing capacities [START_REF] Ekdale | Form and function of the mammalian inner ear[END_REF]. However, this method is imprecise and found products should not be compared with too much detail. This only allows us to grossly

Chapter cover illustrations

Chapter I

Reconstitution of Phosphatherium escuilliei (illustration by Dominique Visset) with the skull seen in transparency and with a focus on the petrosal and the labyrinth.

Chapter II

Skull of an African forest elephant with the petrosal seen in transparency. Illustration of the petrosal of an African forest elephant (Charlène Letenneur, CR2P-MNHN). 3D reconstruction of the bony labyrinth and the ossicular chain of an African elephant.

Chapter III

3D reconstruction of the petrosal of Stegomastodon sp., with the natural cast of the bony labyrinth visible at the surface, with the bony labyrinth seen in transparency, and with the labyrinth only.

Chapter IV

Bony labyrinth of an elephant with the landmarks sets used in the thesis seen in transparency.

Chapter V

Bony labyrinths of extinct and extant proboscideans (from the smallest to the largest: Eritherium, Phosphatherium, Numidotherium, Mammut, Platybelodon, Stegomastodon, Gomphotherium, Stegodon, Anancus, Elephas and Loxodonta). The figure is not in scale.

Chapter VI

Membranous semicircular ducts seen in transparency in the bony labyrinth of Procavia, Elephantulus and Elephas. The membranous saccule and cochlear duct are not represented.

Chapter VII

Bony labyrinth of Gomphotherium angustidens and schematic representation of infrasound waves.

Appendix 2 -Illustrations of the phylogenetic characters used in the preliminary cladistic analysis performed on proboscideans. ASC = Anterior semicircular canal ; LSC = Lateral semicircular canal ; PSC = Posterior semicircular canal (3 pages).

443

Appendix 3 -Matrix used in the preliminary cladistic analysis performed on proboscideans.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Zhelestid 0 0 (01) 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 Henkelotherium 0 0 ? ? 1 ? ? 1 0 0 ? ? 0 ? ? 0 0 0 Eritherium 0 0 1 0 1 1 1 0 1 0 1 0 1 0 0 0 1 0 Phosphatherium 1 0 1 1 0 0 1 0 0 1 0 0 0 0 0 ? ? 0 Numidotherium 1 0 0 1 0 0 1 1 ? 1 0 0 0 0 ? 0 1 0 Moeritherium 1 1 1 ? 0 ? 1 0 ? 1 ? ? ? ? ? 1 ? ? Gomphotherium 2 1 ? 0 0 0 1 0 0 1 ? ? ? ? ? ? ? ? Elephantidae 2 1 1 ? 0 0 1 0 0 1 0 1 2 1 1 0 1 1 Appendix 4 -Cladogram obtained in the analysis extended to the Afrotheria with its associated matrix. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Henkelotherium 0 0 ? ? 1 ? ? 1 0 0 ? ? 0 ? ? 0 0 0 Zhelestids 0 0 (01) 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 Protungulatum 0 0 0 0 1 0 0 1 ? 1 ? ? ? ? ? ? ? ? Diacodexis 0 0 0 1 ? 0 ? ? 0 ? 0 0 0 0 1 0 1 0 Dasypus 1 0 0 0 0 0 1 1 0 1 ? 0 2 0 0 0 1 0 Ocepeia 0 0 0 0 0 1 1 0 1 ? 1 0 1 0 0 0 1 0 Orycteropus 1 0 1 ? 0 1 0 1 0 1 0 0 0 0 ? 0 1 0 Chambius 0 0 0 0 0 1 0 1 0 1 0 0 0 0 ? 1 1 0 Potamogale 0 0 1 0 1 0 0 1 0 1 ? 0 2 0 0 1 1 0 Procavia 1 0 0 0 1 0 1 0 ? 1 1 1 2 0 0 1 1 0 Arsinoitherium 2 1 1 ? 0 0 1 0 0 1 0 1 0 1 1 0 1 0 Chambi sirenian ? ? 0 0 0 1 1 0 0 1 1 0 0 0 ? 1 1 1 Prorastomus 2 0 1 ? 0 1 1 0 0 1 1 0 2 0 1 0 1 0 Trichechus 2 1 1 ? ? ? 1 0 ? 1 1 0 2 0 1 0 0 1 Eritherium 0 0 1 0 1 1 1 0 1 0 1 0 1 0 0 0 1 0 Phosphatherium 1 0 1 1 0 0 1 0 0 1 0 0 0 0 0 ? ? 0 Numidotherium 1 0 0 1 0 0 1 1 ? 1 0 0 0 0 ? 0 1 0 Moeritherium 1 1 1 ? 0 ? 1 0 ? ? ? ? ? ? ? 1 ? ? Gomphotherium 2 1 ? 0 0 0 1 0 0 1 ? ? ? ? ? ? ? ? Elephantoidea 2 1 1 ? 0 0 1 0 0 1 0 1 2 1 1 0 1 1

Henkelotherium and zhelestids were defined as outgroups. Characters are unordered. This topology was found after a heuristic search with PAUP 3. Anancus

Embrithopoda PM53

Mammuthus primigenius Anancus

Arsinoitherium Elephantimorpha ?

Helioseus

M. primigenius

Numidotherium

Appendix 26 -Parameters of the phylogenetic characters used in the analysis focused on the Proboscidea. 'NI' is for not informative. Appendix 27 -Strict consensus of the 18 most parsimonious trees obtained for the implied weighting analysis performed on proboscideans. Length = 66; CI = 0.579; RI = 0.922. Except for the implied weighting, the parameters of the analysis are the same as the unweighted analysis presented in Chapter V. The software TNT was used instead of PAUP. The multistate characters are ordered.

Appendix 28A -Parameters of the phylogenetic characters used in the unweighted analysis extended to the Afrotheria. 'NI' is for not informative. Appendix 30 -Script used to infer the functional capacities of extinct and extant proboscideans and afrotherians with R (7 pages)

library(phytools) library(caper) library(geiger) library(rgl) library(calibrate) library(MASS) library(geometry)

joint.lambda<-function(tree,X){ result<-optimize(f=likMlambda,X=X,C=vcv(tree),interval=c(0,1), maximum=TRUE) return(list(lambda=result$maximum,logL=result$objective [1]) [,16:30] Function_Subset_AVERAGE = cbind (Function_AVERAGE[,[START_REF] Benoit | Shape of the fenestra vestibuli[END_REF]rowMeans(Function_AVERAGE[,1:2]),rowMeans (Function_AVERAGE[,1:3]),Functi on_AVERAGE [,6],rowMeans(Function_AVERAGE[,4:5]), rowMeans (Function_AVERAGE[,4:6]), Function_AVERAGE[,9],rowMeans(Function_AVERAGE[,7:8]),rowMeans (F unction_AVERAGE[,7:9]), Function_AVERAGE[,12],rowMeans(Function_AVERAGE[,10:11]),rowMeans (Function_ AVERAGE[,10:12]), Function_AVERAGE[,[START_REF] Benoit | lateral semicircular canal[END_REF]rowMeans(Function_AVERAGE[,13:14]),rowMeans (Function_AVERAGE[,13:15])) colnames(Function_Subset_AVERAGE)=c("T1_H", "T1_V", "T1_M", "T2_H", "T2_V", "T2_M", "w0_H", "w0_V", "w0_M", "VG_H", "VG_V", "VG_M", "AG_H", "AG_V", "AG_M") (Names_AVERAGE,Function_Subset_AVERAGE_LOG,Morpho_AVERAGE_LOG,PCA_Morpho_AVERAGE_LOG$x[,1:5]) PGLS_T1_H = pgls(T1_H~PC1+PC2+PC3+PC4,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_T1_V = pgls(T1_V~PC1+PC2,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_T1_M = pgls(T1_M~PC1+PC2,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_T2_H = pgls(T2_H~PC1+PC2+PC3+PC4+PC5,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_T2_V = pgls(T2_V~PC1+PC2+PC3+PC4+PC5,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_T2_M = pgls(T2_M~PC1+PC2+PC3+PC4+PC5,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_w0_H = pgls(w0_H~PC1+PC2+PC3,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_w0_V = pgls(w0_V~PC1+PC2,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_w0_M = pgls(w0_M~PC1+PC2+PC3,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_VG_H = pgls(VG_H~PC1,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_VG_V = pgls(VG_V~PC1+PC2+PC3+PC4+PC5,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_VG_M = pgls(VG_M~PC1+PC2+PC3+PC4+PC5,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_AG_H = pgls(AG_H~PC1+PC2+PC3,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_AG_V = pgls(AG_V~PC1+PC2+PC3+PC4+PC5,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") PGLS_AG_M = pgls(AG_M~PC1+PC2+PC3+PC4+PC5,comparative.data(TREE,PGLS_SET,B_Taxa),lambda = "ML") ((predict(PGLS_T1_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:4]))+fastAnc(TREE,PGLS_T1_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_T1_V, as.data.frame (PCA_Morpho_BONY_LOG_x[,1:2]))+fastAnc(TREE,PGLS_T1_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_T1_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:2]))+fastAnc(TREE,PGLS_T1_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_T2_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_T2_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), predict(PGLS_T2_V, as.data.frame (PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_T2_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), predict(PGLS_T2_M, as.data.frame (PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_T2_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_w0_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:3]))+fastAnc(TREE,PGLS_w0_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_w0_V,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:2]))+fastAnc(TREE,PGLS_w0_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_w0_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:3]))+fastAnc(TREE,PGLS_w0_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_VG_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1,drop=FALSE]))+fastAnc(TREE,PGLS_VG_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_VG_V, as.data.frame (PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_VG_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict (PGLS_VG_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_VG_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_AG_H, as.data.frame(PCA_Morpho_BONY_LOG_x[,1:3]))+fastAnc(TREE,PGLS_AG_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), 480 (predict(PGLS_AG_V,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_AG_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict (PGLS_AG_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_AG_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF])) fastAnc(TREE,PGLS_T1_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1] fastAnc(TREE,PGLS_T1_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2] fastAnc(TREE,PGLS_T1_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF] Fitted_Function_BONY = 10^(Fitted_Function_BONY_LOG) Fitted_Function_AVERAGE_LOG = cbind ((predict(PGLS_T1_H,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:4]))+fastAnc(TREE,PGLS_T1_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), predict(PGLS_T1_V, as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:2]))+fastAnc(TREE,PGLS_T1_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_T1_M, as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:2]))+fastAnc(TREE,PGLS_T1_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_T2_H, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_T2_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_T2_V, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_T2_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_T2_M, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_T2_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_w0_H, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:3]))+fastAnc(TREE,PGLS_w0_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_w0_V, as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:2]))+fastAnc(TREE,PGLS_w0_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_w0_M, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:3]))+fastAnc(TREE,PGLS_w0_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_VG_H, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1,drop=FALSE]))+fastAnc(TREE,PGLS_VG_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_VG_V, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_VG_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_VG_M, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_VG_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_AG_H, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:3]))+fastAnc(TREE,PGLS_AG_H$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_AG_V, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_AG_V$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]), (predict(PGLS_AG_M, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_AG_M$residuals,CI=TRUE)$ace [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF])) Fitted_Function_AVERAGE = 10^(Fitted_Function_AVERAGE_LOG) Lower_Function_BONY_LOG = cbind ((predict(PGLS_T1_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:4]))+fastAnc(TREE,PGLS_T1_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_T1_V, as.data.frame(PCA_Morpho_BONY_LOG_x[,1:2]))+fastAnc(TREE,PGLS_T1_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_T1_M, as.data.frame(PCA_Morpho_BONY_LOG_x[,1:2]))+fastAnc(TREE,PGLS_T1_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_T2_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_T2_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_T2_V, as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_T2_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_T2_M, as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_T2_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), 481 (predict(PGLS_w0_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:3]))+fastAnc(TREE,PGLS_w0_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_w0_V,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:2]))+fastAnc(TREE,PGLS_w0_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_w0_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:3]))+fastAnc(TREE,PGLS_w0_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_VG_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1,drop=FALSE]))+fastAnc(TREE,PGLS_VG_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_VG_V,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_VG_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_VG_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_VG_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_AG_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:3]))+fastAnc(TREE,PGLS_AG_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_AG_V, as.data.frame (PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_AG_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]), (predict(PGLS_AG_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_AG_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]))

482

(predict(PGLS_AG_V, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_AG_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1]) , (predict(PGLS_AG_M,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_AG_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]1] )) Lower_Function_AVERAGE = 10^(Lower_Function_AVERAGE_LOG) Upper_Function_BONY_LOG = cbind ((predict(PGLS_T1_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:4]))+fastAnc(TREE,PGLS_T1_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_T1_V,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:2]))+fastAnc(TREE,PGLS_T1_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_T1_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:2]))+fastAnc(TREE,PGLS_T1_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_T2_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_T2_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_T2_V,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_T2_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_T2_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_T2_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_w0_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:3]))+fastAnc(TREE,PGLS_w0_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_w0_V,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:2]))+fastAnc(TREE,PGLS_w0_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_w0_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:3]))+fastAnc(TREE,PGLS_w0_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_VG_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1,drop=FALSE]))+fastAnc(TREE,PGLS_VG_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_VG_V,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_VG_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_VG_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_VG_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_AG_H,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:3]))+fastAnc(TREE,PGLS_AG_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_AG_V,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_AG_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_AG_M,as.data.frame(PCA_Morpho_BONY_LOG_x[,1:5]))+fastAnc(TREE,PGLS_AG_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2])) Upper_Function_BONY = 10^(Upper_Function_BONY_LOG) Upper_Function_AVERAGE_LOG = cbind ((predict(PGLS_T1_H,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:4]))+fastAnc(TREE,PGLS_T1_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_T1_V, as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:2]))+fastAnc(TREE,PGLS_T1_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_T1_M,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:2]))+fastAnc(TREE,PGLS_T1_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]) , (predict(PGLS_T2_H,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_T2_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_T2_V, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_T2_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_T2_M, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_T2_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]) , 483 (predict(PGLS_w0_H,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:3]))+fastAnc(TREE,PGLS_w0_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]) , (predict(PGLS_w0_V,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:2]))+fastAnc(TREE,PGLS_w0_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]) , (predict(PGLS_w0_M,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:3]))+fastAnc(TREE,PGLS_w0_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2] ), (predict(PGLS_VG_H,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1,drop=FALSE]))+fastAnc(TREE,PGLS_VG_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]), (predict(PGLS_VG_V, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_VG_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]) , (predict(PGLS_VG_M, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_VG_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2] ), (predict(PGLS_AG_H,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:3]))+fastAnc(TREE,PGLS_AG_H$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]) , (predict(PGLS_AG_V,as.data.frame(PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_AG_V$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2]) , (predict(PGLS_AG_M, as.data.frame (PCA_Morpho_AVERAGE_LOG$x[,1:5]))+fastAnc(TREE,PGLS_AG_M$residuals,CI=TRUE)$CI95 [START_REF]the tegmen tympani: (0) poorly developed, (1) prominent and inflated prominent, (2) forming a flat and large cerebral surface[END_REF]2] ))

Appendix 31 -Calculation of the low-frequency limit estimates in proboscideans using the equations of [START_REF] West | The relationship of the spiral turns of the cochlea and the length of the basilar membrane to the range of audible frequencies in ground dwelling mammals[END_REF]