Alessandro Urciuoli
email: alessandro.urciuoli@icp.cat

Clément Zanolli

Amélie Beaudet

Marta Pina

Sergio Almécija

Salvador Moyà-Solà

David M Alba
email: david.alba@icp.cat

A comparative analysis of the vestibular apparatus in Epipliopithecus vindobonensis: Phylogenetic implications

Keywords: Pliopithecidae, Catarrhini, Miocene, Inner ear, Phylogeny, Geometric morphometrics 1

établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The phylogenetic position of pliopithecoids

Pliopithecoids are an extinct superfamily of catarrhine primates, recorded in Eurasia from the early to the late Miocene [START_REF] Andrews | Distribution and biochronology of European and Southwest Asian Miocene catarrhines[END_REF][START_REF] Begun | The Pliopithecoidea[END_REF][START_REF] Begun | Evolution of the Pliopithecoidea[END_REF][START_REF] Harrison | The zoogeographic and phylogenetic relationships of early catarrhine primates in Asia[END_REF][START_REF] Harrison | Catarrhine origins[END_REF]. Their first occurrence, in the early Miocene of China (~18-17 Ma; [START_REF] Harrison | Taxonomy and phylogenetic relationships of early Miocene catarrhines from Sihong, China[END_REF][START_REF] Begun | The Pliopithecoidea[END_REF][START_REF] Harrison | Catarrhine origins[END_REF], slightly predates the oldest record of largebodied apes in Eurasia (Heizmann and Begun, 2001;[START_REF] Casanovas-Vilar | Updated chronology for the Miocene hominoid radiation in Western Eurasia[END_REF]. In the absence of older (earliest Miocene) catarrhines in that continent, pliopithecoids are assumed to have an African origin [START_REF] Harrison | The phylogenetic relationships of the early catarrhine primates: a review of the current evidence[END_REF][START_REF] Harrison | Catarrhine origins[END_REF][START_REF] Begun | Evolution of the Pliopithecoidea[END_REF]. Like apes, pliopithecoid ancestors probably dispersed into Eurasia before the Langhian transgression, which was possible due to the lowered sea level and tectonic events that led to the closure of the Tethys Seaway and the establishment of an intermittent terrestrial corridor beginning at ~19 Ma [START_REF] Harzhauser | Biogeographic responses to geodynamics: A key study all around the Oligo-Miocene Tethyan Seaway[END_REF][START_REF] Harrison | Catarrhine origins[END_REF].

Decades ago, pliopithecoids were considered to be phylogenetically related to hylobatids due to some superficial resemblances in cranial morphology as well as body size and proportions (e.g., [START_REF] Hürzeler | Contribution a l'odontologie et a la phylogénèse du genre Pliopithecus Gervais[END_REF][START_REF] Zapfe | The skeleton of Pliopithecus (Epipliopithecus) vindobonensis Zapfe and Hürzeler[END_REF]Zapfe, , 1960[START_REF] Zapfe | Die Primatenfunde aus der miozänen Spaltenfüllung von Neudorf an der March (Děvínská Nová Ves)[END_REF][START_REF] Simons | The history of extinct gibbon-like primates[END_REF]. Currently, they are generally considered a clade of stem catarrhines-as supported by the retention of several cranial and postcranial features that are plesiomorphic compared to the crown members of the group [START_REF] Delson | Evolution and interrelationships of the catarrhine primates[END_REF][START_REF] Ciochon | The phenetic position of Pliopithecus and its phylogenetic relationship to the Hominoidea[END_REF][START_REF] Fleagle | Are there any fossil gibbons?[END_REF][START_REF] Harrison | The phylogenetic relationships of the early catarrhine primates: a review of the current evidence[END_REF][START_REF] Harrison | The zoogeographic and phylogenetic relationships of early catarrhine primates in Asia[END_REF][START_REF] Harrison | Catarrhine origins[END_REF][START_REF] Andrews | Distribution and biochronology of European and Southwest Asian Miocene catarrhines[END_REF][START_REF] Begun | The Pliopithecoidea[END_REF][START_REF] Begun | Evolution of the Pliopithecoidea[END_REF]. The divergence of pliopithecoids before the split of crown catarrhines is further supported by most recent cladistic analyses [START_REF] Zalmout | New Oligocene primate from Saudi Arabia and the divergence of apes and Old World monkeys[END_REF][START_REF] Stevens | Palaeontological evidence for an Oligocene divergence between Old World monkeys and apes[END_REF][START_REF] Nengo | New infant cranium from the African Miocene sheds light on ape evolution[END_REF][START_REF] Gilbert | New middle Miocene ape (Primates: Hylobatidae) from Ramnagar, India fills major gaps in the hominoid fossil record[END_REF], implying a long ghost lineage of ca. 12-14 Myr for pliopithecoids [START_REF] Begun | Evolution of the Pliopithecoidea[END_REF]. The exception is the cladistic analysis by [START_REF] Alba | Miocene small-bodied ape from Eurasia sheds light on hominoid evolution[END_REF], which recovered pliopithecoids as a clade of stem hominoids-thereby eliminating the need to hypothesize a long gap in the pliopithecoid fossil record. Most recently, Almécija et al. (2019) further documented similarities in femoral morphology between pliopithecoids (Epipliopithecus) and extant hominoids, thereby casting additional doubts on the status of pliopithecoids as stem catarrhines. Further uncertainty in this regard stems from the fact that no tail vertebrae are known from pliopithecoids [START_REF] Begun | Evolution of the Pliopithecoidea[END_REF]. Based on sacral morphology, [START_REF] Zapfe | The skeleton of Pliopithecus (Epipliopithecus) vindobonensis Zapfe and Hürzeler[END_REF][START_REF] Zapfe | Die Primatenfunde aus der miozänen Spaltenfüllung von Neudorf an der March (Děvínská Nová Ves)[END_REF] argued that no external tail would have been present, as in hominoids; although this has subsequently been rebutted [START_REF] Ankel | Der Canalis Sacralis als Indikator für die Länge der Caudalregion der Primaten[END_REF][START_REF] Russo | Comparative sacral morphology and the reconstructed tail lengths of five extinct primates: Proconsul heseloni, Epipliopithecus vindobonensis, Archaeolemur edwardsi, Megaladapis grandidieri, and Palaeopropithecus kelyus[END_REF], available evidence in this regard remains uncertain.

There are multiple genera of pliopithecids [START_REF] Harrison | Taxonomy and phylogenetic relationships of early Miocene catarrhines from Sihong, China[END_REF][START_REF] Moyà-Solà | Egarapithecus narcisoi, a new genus of Pliopithecidae (Primates, Catarrhini) from the late Miocene of Spain[END_REF][START_REF] Begun | The Pliopithecoidea[END_REF][START_REF] Begun | Evolution of the Pliopithecoidea[END_REF][START_REF] Harrison | The zoogeographic and phylogenetic relationships of early catarrhine primates in Asia[END_REF][START_REF] Harrison | Catarrhine origins[END_REF][START_REF] Alba | A new species of Pliopithecus Gervais, 1849 (Primates: Pliopithecidae) from the Middle Miocene (MN8) of Abocador de Can Mata (els Hostalets de Pierola, Catalonia, Spain)[END_REF][START_REF] Alba | A new pliopithecid genus (Primates: Pliopithecoidea) from Castell de Barberà (Vallès-Penedès Basin, Catalonia, Spain)[END_REF][START_REF] Alba | On the holotype and original description of the pliopithecid Plesiopliopithecus lockeri (Zapfe, 1960)[END_REF][START_REF] Sankhyan | A highly derived pliopithecoid from the Late Miocene of Haritalyangar, India[END_REF][START_REF] Harrison | A new genus of pliopithecoid from the late Early Miocene of China and its implications for understanding the paleozoogeography of the Pliopithecoidea[END_REF], which, following [START_REF] Harrison | A new genus of pliopithecoid from the late Early Miocene of China and its implications for understanding the paleozoogeography of the Pliopithecoidea[END_REF], we provisionally group into four different families: dionysopithecids (Dionysopithecus and Platodontopithecus), krishnapithecids (Krishnapithecus), pliopithecids (Pliopithecus and Epipliopithecus), and crouzeliids (Plesiopliopithecus, Barberapithecus, Anapithecus, Egarapithecus, and Laccopithecus).

However, it is noteworthy that the treatment of these genera at the family rank, and even the placing of some genera in one or another group, differs among authors (e.g., compare Alba andMoyà-Solà, 2012 with Begun, 2017). Such disagreements largely stem from the fact that the internal phylogeny of pliopithecoids is still unclear and that their affinities with fossil catarrhines from Africa remain uncertain (e.g., [START_REF] Harrison | Catarrhine origins[END_REF].

Evidence from Epipliopithecus

Deciphering the phylogenetic relationships of most pliopithecoids is hampered by the fact that they are mostly known by fragmentary dentognathic remains, with the exception of Epipliopithecus vindobonensis, whose craniodental and postcranial morphology is well documented by several skeletons from the middle Miocene (MN6, ~14.85-13.45 Ma 1 ) karstic infillings of Devínska Nová Ves, Slovakia [START_REF] Zapfe | The skeleton of Pliopithecus (Epipliopithecus) vindobonensis Zapfe and Hürzeler[END_REF][START_REF] Zapfe | Die Primatenfunde aus der miozänen Spaltenfüllung von Neudorf an der March (Děvínská Nová Ves)[END_REF][START_REF] Andrews | Distribution and biochronology of European and Southwest Asian Miocene catarrhines[END_REF][START_REF] Begun | The Pliopithecoidea[END_REF][START_REF] Harrison | Catarrhine origins[END_REF]. Epipliopithecus was originally established as a subgenus of Pliopithecus by [START_REF] Zapfe | Die Fauna der miozänen Spaltenfüllung von Neudorf an der March (ČSR.)[END_REF], being subsequently considered a junior subjective synonym of the latter (e.g., [START_REF] Andrews | Distribution and biochronology of European and Southwest Asian Miocene catarrhines[END_REF][START_REF] Harrison | Taxonomy and phylogenetic relationships of early Miocene catarrhines from Sihong, China[END_REF][START_REF] Moyà-Solà | Egarapithecus narcisoi, a new genus of Pliopithecidae (Primates, Catarrhini) from the late Miocene of Spain[END_REF][START_REF] Harrison | The zoogeographic and phylogenetic relationships of early catarrhine primates in Asia[END_REF][START_REF] Harrison | Catarrhine origins[END_REF][START_REF] Alba | A new species of Pliopithecus Gervais, 1849 (Primates: Pliopithecidae) from the Middle Miocene (MN8) of Abocador de Can Mata (els Hostalets de Pierola, Catalonia, Spain)[END_REF] or a distinct genus (e.g., [START_REF] Begun | The Pliopithecoidea[END_REF][START_REF] Alba | A new pliopithecid genus (Primates: Pliopithecoidea) from Castell de Barberà (Vallès-Penedès Basin, Catalonia, Spain)[END_REF][START_REF] Arias-Martorell | Morphological affinities of the proximal humerus of Epipliopithecus vindobonensis and Pliopithecus antiquus: Suspensory inferences based on a 3D geometric morphometrics approach[END_REF][START_REF] Alba | Miocene small-bodied ape from Eurasia sheds light on hominoid evolution[END_REF]this study). From a locomotor viewpoint, E. vindobonensis has been variously depicted as an arboreal or semiterrestrial generalized quadruped with varying degrees of climbing and suspensory abilities (see discussion in [START_REF] Arias-Martorell | Morphological affinities of the proximal humerus of Epipliopithecus vindobonensis and Pliopithecus antiquus: Suspensory inferences based on a 3D geometric morphometrics approach[END_REF]. From a phylogenetic perspective, its purported stem catarrhine status has been supported by features such as the short and only partially enclosed ectotympanic, the presence of entepicondylar foramen in the distal humerus, and single hinge-like carpometacarpal joint in the thumb [START_REF] Zapfe | Die Primatenfunde aus der miozänen Spaltenfüllung von Neudorf an der March (Děvínská Nová Ves)[END_REF][START_REF] Szalay | Evolutionary History of the Primates[END_REF][START_REF] Harrison | The phylogenetic relationships of the early catarrhine primates: a review of the current evidence[END_REF][START_REF] Harrison | The zoogeographic and phylogenetic relationships of early catarrhine primates in Asia[END_REF][START_REF] Andrews | Distribution and biochronology of European and Southwest Asian Miocene catarrhines[END_REF][START_REF] Begun | The Pliopithecoidea[END_REF][START_REF] Begun | Evolution of the Pliopithecoidea[END_REF].

1 Age uncertainly based on the boundaries recognized for MN6 (van der Meulen et al., 2011).

The external morphology of the petrosal bone of E. vindobonensis [START_REF] Zapfe | Die Primatenfunde aus der miozänen Spaltenfüllung von Neudorf an der March (Děvínská Nová Ves)[END_REF][START_REF] Szalay | Phylogeny of primate higher taxa: the basicranial evidence[END_REF][START_REF] Fricano | The primate ectotympanic tube: correlates of structure, function, and development[END_REF] has been of utmost significance in the discussion of its phylogenetic affinities, given that the presence of a tubular ectotympanic is considered synapomorphic of crown catarrhines (e.g., [START_REF] Szalay | Phylogeny of primate higher taxa: the basicranial evidence[END_REF][START_REF] Szalay | Evolutionary History of the Primates[END_REF][START_REF] Harrison | The phylogenetic relationships of the early catarrhine primates: a review of the current evidence[END_REF][START_REF] Harrison | The zoogeographic and phylogenetic relationships of early catarrhine primates in Asia[END_REF][START_REF] Andrews | Distribution and biochronology of European and Southwest Asian Miocene catarrhines[END_REF][START_REF] Begun | The Pliopithecoidea[END_REF][START_REF] Zalmout | New Oligocene primate from Saudi Arabia and the divergence of apes and Old World monkeys[END_REF][START_REF] Alba | Miocene small-bodied ape from Eurasia sheds light on hominoid evolution[END_REF][START_REF] Nengo | New infant cranium from the African Miocene sheds light on ape evolution[END_REF]. The possibility remains that such ossification took place to some extent independently in cercopithecoids, hominoids and/or other anthropoids such as pliopithecoids [START_REF] Begun | The Pliopithecoidea[END_REF][START_REF] Begun | Evolution of the Pliopithecoidea[END_REF][START_REF] Alba | Miocene small-bodied ape from Eurasia sheds light on hominoid evolution[END_REF]. However, other features of Epipliopithecus also appear plesiomorphic as compared to crown catarrhines and show no particular similarities with hominoids, namely: the large postglenoid process separated from the acoustic meatus, as in platyrrhines [START_REF] Zapfe | Die Primatenfunde aus der miozänen Spaltenfüllung von Neudorf an der March (Děvínská Nová Ves)[END_REF]; the lack of ossification in the tentorium cerebelli (unlike in most platyrrhines and stem anthropoids, but similar to Aegyptopithecus and crown catarrhines; Kay et al., 2009a); and the deep subarcuate fossa [START_REF] Zapfe | Die Primatenfunde aus der miozänen Spaltenfüllung von Neudorf an der March (Děvínská Nová Ves)[END_REF], as in platyrrhines and most anthropoids except hominids (Gannon et al., 1988;[START_REF] Kunimatsu | Loss of the subarcuate fossa and the phylogeny of Nacholapithecus[END_REF]. In contrast, the inner ear morphology of Epipliopithecus has not been described and therefore its potential phylogenetic implications remain unexplored.

The bony labyrinth of the inner ear

Among the inner cavities of the petrosal, the bony labyrinth of the inner ear is constituted by the semicircular canals (SCs) and the vestibule (which together host the soft-tissue structures linked with the sense of balance) plus the cochlea. Semicircular canal size (e.g., [START_REF] Spoor | The primate semicircular canal system and locomotion[END_REF][START_REF] Silcox | Semicircular canal system in early primates[END_REF][START_REF] Ryan | Evolution of locomotion in Anthropoidea: the semicircular canal evidence[END_REF][START_REF] Grohé | Recent inner ear specialization for high-speed hunting in cheetahs[END_REF] and orientation [START_REF] David | Motion from the past. A new method to infer vestibular capacities of extinct species[END_REF][START_REF] Malinzak | Locomotor head movements and semicircular canal morphology in primates[END_REF][START_REF] Berlin | Functional implications of ubiquitous semicircular canal non-orthogonality in mammals[END_REF][START_REF] Perier | Different level of intraspecific variation of the bony labyrinth morphology in slow-versus fast-moving Primates[END_REF][START_REF] Gonzales | Intraspecific variation in semicircular canal morphology-A missing element in adaptive scenarios?[END_REF] have been frequently used for inferring agility, while the shape of the canals as a whole has tentatively been linked to positional behavior (Le [START_REF] Maître | New data about semicircular canal morphology and locomotion in modern hominoids[END_REF]. At the same time, recent studies have demonstrated that the SCs bear strong phylogenetic signal among anthropoids [START_REF] Lebrun | Deep evolutionary roots of strepsirrhine primate labyrinthine morphology[END_REF][START_REF] Lebrun | The labyrinthine morphology of Pronycticebus gaudryi (Primates, Adapiformes)[END_REF][START_REF] Urciuoli | A deformation-based geometric morphometric analysis of the vestibular apparatus in the Miocene apes Hispanopithecus laietanus and Rudapithecus hungaricus[END_REF][START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF][START_REF] Del Rio | Allometry, function and shape diversification in the inner ear of platyrrhine primates[END_REF][START_REF] Morimoto | Variation of bony labyrinthine morphology in Mio-Plio-Pleistocene and modern anthropoids[END_REF] and other mammals (e.g., [START_REF] Grohé | Bony labyrinth shape variation in extant Carnivora: a case study of Musteloidea[END_REF]Mennecart et al., 2016[START_REF] Mennecart | Bony labyrinth morphology clarifies the origin and evolution of deer[END_REF][START_REF] Costeur | The bony labyrinth of toothed whales reflects both phylogeny and habitat preferences[END_REF].

Although adaptively relevant characters may constitute synapomorphies of particular clades, arguably their relationship with function makes them potentially more prone to homoplasy. However, the correlation between SC morphology and positional behavior has recently been questioned by some studies (i.e., [START_REF] Rae | Semicircular canal size and locomotion in colobine monkeys: a cautionary tale[END_REF]del Río et al., 2020;[START_REF] Morimoto | Variation of bony labyrinthine morphology in Mio-Plio-Pleistocene and modern anthropoids[END_REF], and SC shape variation has been shown to largely follow the expectations of a Brownian motion mode of evolution in both platyrrhines (del Río et al., 2020) and catarrhines [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF]. These results are in accordance with those obtained for the bony labyrinth as a whole, showing that its morphology reflects phylogenetic relatedness as inferred from molecular data [START_REF] Lebrun | Deep evolutionary roots of strepsirrhine primate labyrinthine morphology[END_REF][START_REF] Ekdale | Comparative anatomy of the bony labyrinth (inner ear) of placental mammals[END_REF][START_REF] Macrini | Comparative study of notoungulate (Placentalia, Mammalia) bony labyrinths and new phylogenetically informative inner ear characters[END_REF][START_REF] Billet | Morphological diversity of the bony labyrinth (inner ear) in extant xenarthrans and its relation to phylogeny[END_REF]. Cumulatively, this evidence suggests that bony labyrinth morphology is phylogenetically informative among mammals [START_REF] Mennecart | Bony labyrinth morphology clarifies the origin and evolution of deer[END_REF] and may thus potentially illuminate the phylogenetic relationships of extinct primates. Following Mennecart and Costeur (2016), who suggested that inner ear structures might be highly informative for large cladistics analyses, [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF] explored catarrhine SC shape variation among catarrhines and proposed several potential synapomorphies for crown hominoids.

Here we test between two different phylogenetic hypotheses for Epipliopithecus, one hypothesis being that Epipliopithecus is a stem catarrhine, the other hypothesis that Epipliopithecus is a hominoid, based on the information provided by the shape of the SCs and vestibule. This morphology is described here for the first time using a threedimensional geometric morphometric (3DGM) approach applied to a broad sample of extant and fossil anthropoids [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF]. We refrained from analyzing the entire bony labyrinth (i.e., including also the cochlea) because its potential for phylogenetic reconstruction among primates is currently unclear. A recent analysis in platyrrhines suggested that cochlear shape departs from a Brownian motion mode of evolution (Blomberg's K < 1;del Río et al., 2020), thus potentially reflecting a greater influence of function (and likely homoplasy due to similar selection pressures) than is the case for the SCs and vestibule. This is in agreement with previous studies linking several macroscopic cochlear features to hearing capabilities (e.g., [START_REF] Manoussaki | Cochlea's graded curvature effect on low frequency waves[END_REF][START_REF] Kirk | Cochlear labyrinth volume and hearing abilities in primates[END_REF][START_REF] Coleman | Correlations between auditory structures and hearing sensitivity in non-human primates[END_REF]. More detailed morphometric analyses of this structure among anthropoids is thus required to determine whether cochlear morphology can be meaningfully used to decipher the phylogenetic relationships of extinct catarrhines such as Epipliopithecus.

Materials and methods

Described material

We inspected three petrosals of E. vindobonensis belonging to two individuals from Devínska Nová Ves, Slovakia (Zapfe, 1960[START_REF] Zapfe | Die Primatenfunde aus der miozänen Spaltenfüllung von Neudorf an der March (Děvínská Nová Ves)[END_REF]

Comparative sample

The comparative sample includes μCT scans of 162 dried crania and temporal bones belonging to 31 extant anthropoid species (see Supplementary Online Material

[SOM] Table S1 for the sample size of the extant species), plus five fossil anthropoids (SOM Table S2): the stem anthropoid Parapithecus [START_REF] Bush | Endocranial volume and optic foramen size in Parapithecus grangeri[END_REF], the stem catarrhine Aegyptopithecus [START_REF] Simons | A remarkable female cranium of the early Oligocene anthropoid Aegyptopithecus zeuxis (Catarrhini, Propliopithecidae)[END_REF], the stem platyrrhines Dolichocebus (Kay et al., 2009b) and Homunculus [START_REF] Fulwood | Stem members of Platyrrhini are distinct from catarrhines in at least one derived cranial feature[END_REF], and the hominoid Oreopithecus [START_REF] Rook | The bony labyrinth of Oreopithecus bambolii[END_REF]. et al. (2020: Supplementary File 1). The slice stacks of these crania were processed using Avizo v. 9.0.1. and the left bony labyrinth was segmented using the semiautomatic 'watershed' tool of Avizo (with additional manual corrections in the case of partially filled canals found in the fossil specimens) and digitally extracted; when the left bony labyrinth was unavailable, the right one was mirrored. As in [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF], the SCs and the vestibule were separated from the cochlea by cutting the generated 3D meshes immediately inferior to the saccule and the oval window, using landmarks placed along the maximum curvature of the junction between the vestibule and the cochlea as reference for the cutting plane (Fig. 1). The resulting holes were filled with a flat surface using Geomagic Studio v. 2014.3.0 (3D Systems, Rock Hill, USA). Prior to the 3DGM analysis, the surfaces were first roughly prealigned by manually superimposing the meshes to ensure biological correspondence. Subsequently, the alignment was automatically refined using the Avizo module 'Align Surface' with the 'rigid + uniform' option. Similar to Procrustes superimposition, this module minimizes the distances between the faces of each surface by scaling, translating and rotating the analyzed meshes. The phylogenetic relationships of the extinct taxa included in the analyses, relative to extant anthropoids, are summarized in Figure 2.

Sample preparation

Shape analysis

Differences in vestibule and SC shape were evaluated using a landmark-free 3DGM technique based on deformation, which relies on the geometrical correspondence of continuous surfaces and computes the magnitude and direction of deformation of the analyzed meshes from a group-average template [START_REF] Glaunès | Template estimation form unlabeled point set data and surfaces for Computational Anatomy[END_REF]Durrleman et al., 2012a, b;[START_REF] Dumoncel | Landmark-free 3D method for comparison of fossil hominins and hominids based on endocranium and EDJ shapes[END_REF][START_REF] Beaudet | Upper third molar internal structural organization and semicircular canal morphology in Plio-Pleistocene South African cercopithecoids[END_REF][START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF]. The deformations are mathematically modeled to obtain a one-to-one correspondence of the 3D space using the open-source software Deformetrica 4 [START_REF] Bône | Deformetrica 4: an open-source software for statistical shape analysis[END_REF]. This technique yields results similar to landmark-based 3DGM methods while more easily tracking changes in volume [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF], and is less prone to biases introduced by the design of landmarking protocols, caused by the inherent difficulty to adequately capture complex 3D shapes based on a reduced number of homologous landmarks.

Due to the high computational power required, the sets of vectors, representing the flow of deformations from the initial position of the control points on the template to the target shape, were computed in the Barcelona Supercomputing Center (BSC) using the MinoTauro cluster (https://www.bsc.es/marenostrum/minotauro). To identify major patterns of shape variation across the sample, the resulting sets of vectors were inspected using between-group principal component analysis (bgPCA; [START_REF] Mitteroecker | Linear discrimination, ordination, and the visualization of selection gradients in modern morphometrics[END_REF], using major clades (platyrrhines, cercopithecoids, hylobatids, and hominids) as the grouping factor [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF]. To address recent concerns about the use of bgPCA based on highly multivariate data sets, such as those generated by 3DGM, and to rule out the presence of spurious groupings in our results [START_REF] Bookstein | Pathologies of between-groups principal components analysis in geometric morphometrics[END_REF][START_REF] Cardini | Seeing distinct groups where there are none: Spurious patterns from between-group PCA[END_REF], we computed cross-validated bgPCA scores. These were obtained by iteratively repeating the bgPCA on a subset of the sample. The cross-validated bgPCA scores were then compared to those obtained with standard bgPCA [START_REF] Cardini | Cross-validated between-group PCA scatterplots: A solution to spurious group separation?[END_REF]. The affinities of fossil specimens with the groups defined a priori in the bgPCA were evaluated using the 'typprobClass' function of the Morpho package v. 2.7 [START_REF] Schlager | Morpho and Rvcgshape analysis in R: R-packages for geometric morphometrics, shape analysis and surface manipulations[END_REF] in R v. 3.6.1 (R [START_REF] Core | R: A language and environment for statistical computing[END_REF]. This function computes posterior probabilities of group membership based on the Mahalanobis distances between the bgPC scores of fossil specimens and group centroids. Null hypotheses of group membership were rejected at p < 0.05.

Similarities among anthropoid species were also evaluated by running a cluster analysis (Ward's method) on the Mahalanobis distances between pairs of bgPCA species centroid scores using the 'ward.D2' method of the 'hclust' function of the 'stats' package in R. The cophenetic correlation coefficient, which allows one to evaluate how faithfully the obtained dendrogram preserves the pairwise distances between the original unmodeled datapoints, was calculated using the same package.

In addition, we inspected the volumetric proportions of Epipliopithecus and the remaining fossil taxa included in the analysis, and determined the correlation between log-transformed cube root canal volume (ln VolSC, mm) and log-transformed canal length (ln L, mm) by means of ordinary least-squares regression. Given that previous analyses identified an allometric grade shift between hominids and nonhominid anthropoids [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF], separate regression lines were computed for hominids and nonhominid anthropoid taxa using the 'stats' package in R.

Phylomorphospace, ancestral state estimation, and phylogenetic signal

To intuitively visualize the direction and magnitude of evolutionary change we relied on a phylomorphospace approach [START_REF] Sidlauskas | Continuous and arrested morphological diversification in sister clades of characiform fishes: a phylomorphospace approach[END_REF], by which a phylogenetic tree is projected onto the tangent space defined by the bgPCA of our shape data. Ancestral states for the internal nodes are estimated using a maximum likelihood method for continuous characters via the 'fastAnc' function of the 'phytools' version 0.6-60 package for R [START_REF] Revell | Phytools: an R package for phylogenetic comparative biology (and other things)[END_REF], while the tips of the tree branches correspond to the centroid scores for the included taxa. We repeated the analyses using two composite phylogenetic trees, one with Epipliopithecus as a stem catarrhine and the other with this taxon as a stem hominoid (Figs. 2 and3). For extant taxa we relied on a Bayesian phylogenetic analysis of eleven mitochondrial and six autosomal genes downloaded from the 10kTrees Website v.

3 [START_REF] Arnold | The 10kTrees website: A new online resource for primate phylogeny[END_REF]. Extinct species were added based on their phylogenetic position, [START_REF] Kay | Biogeography in deep time -What do phylogenetics, geology, and paleoclimate tell us about early platyrrhine evolution?[END_REF]; and Oreopithecus 6.75 Ma (mean of 7.0 and 6.5 Ma for the last occurrence according to [START_REF] Rook | Geochronology of Oreopithecusbearing succession at Baccinello (Italy) and the extinction pattern of european miocene hominoids[END_REF].

their
The phylogenetic signal embedded in the shape data was measured using Pagel's λ [START_REF] Pagel | Inferring the historical patterns of biological evolution[END_REF]) and Blomberg's K [START_REF] Blomberg | Testing for phylogenetic signal in comparative data: behavioral traits are more labile[END_REF], together with the multivariate version of Blomberg's K (K mult ; Adams, 2014). Pagel's λ and Blomberg's K were computed using the 'phylosig' function of the 'phytools' package in R, while K mult was computed with the 'physignal' function of the 'geomorph' package v. 3.1.0 in R [START_REF] Collyer | Geomorph: Software for geometric morphometric analyses[END_REF].

These metrics were computed based on extant taxa only [START_REF] Arnold | The 10kTrees website: A new online resource for primate phylogeny[END_REF].

Ancestral node morphologies were computed from the bgPC scores for the last common ancestors (LCAs) estimated by means of maximum likelihood, which were rotated and translated from the morphospace back into the deformation field space, generating a set of momentum vectors that were used in Deformetrica 4 to warp the template surface into the target LCA morphology. Volumetric proportions for the LCAs were computed based on the rescaled 3D models obtained from the phylomorphospace approach; the scaling factor for each LCA was estimated using the 'anc.ML' function of the R package 'phytools'. Morphological similarities between Epipliopithecus and the LCA centroids were assessed by means Euclidean distances between the Epipliopithecus centroid and the LCA bgPC scores, weighted on the basis of the percentage of variance explained by each bgPC and computed using the 'distances' function of the 'distances' package version 0.1.8 in R [START_REF] Savje | distances: tools for distance metrics[END_REF].

The two phylogenetic hypotheses for Epipliopithecus depicted in Figure 3 were assessed further based on the coding of seven discrete characters that were deemed of phylogenetic significance based on shape comparisons and analyses. The resulting character-taxon matrix was analyzed for character congruence against a fixed topology consistent with the phylogenetic hypotheses depicted in Figure 3. For both cladograms, three indices customarily employed in cladistics [START_REF] Farris | The retention index and the rescaled consistency index[END_REF] were computed in PAUP* v.

4.0a168 for Mac [START_REF] Swofford | PAUP*. Phylogenetic Analysis Using Parsimony (*and Other Methods)[END_REF] to assess the most parsimonious hypothesis: the consistency index (CI), the retention index (RI), and the rescaled consistency index (RC).

Results

Description and comparisons

The three bony labyrinths of E. vindobonensis are well preserved-except for the lateral canal of NMB OE 303b, which shows a small fracture in the bony encasing-and are not affected by diagenetic deformation, thereby permitting a straightforward extraction of the 3D surfaces of the vestibular apparatus bony labyrinth (Fig. 4a-c). Overall, the canals are fairly slender, as in platyrrhines and cercopithecins, falling within their variability as shown by a bivariate plot of SC volume vs. length (Fig. 5; Table 2; SOM Table S3). The bony vestibule is large, albeit less so than in hominids. The anterior and posterior canals are larger than the lateral canal, as in platyrrhines (Fig. 4e-i) and modern humans (Fig. 4u).

The E. vindobonensis common crus (CC) is long, as in extant platyrrhines (Fig. 4gi) and in Dolichocebus (Fig. 4e), but unlike in most catarrhines. The trajectories of the anterior and posterior canal form a right angle when merging at the CC apex. Despite some similarities, the morphology of Epipliopithecus is clearly distinguishable from that of Dolichocebus and Parapithecus (Fig. 4d), as the CC is not posteromedially inclined and the anterior canal connection is placed more laterally.

The anterior canal of E. vindobonensis is slightly wider than tall (as in Hoolock; Fig. 4q), yet clearly rounded and lacking the vertical compression characteristic of extant hominoids (Fig. 4o-u), the anterosuperior elongation typical of hylobatids and Pongo (Fig. 4o-r; [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF], and the extreme superior projection found in Ateles (Fig. 4g).

The anterior canal of Epipliopithecus further differs from that of the stem anthropoid Parapithecus (Fig. 4d), the stem platyrrhine Dolichocebus (Fig. 4e), and the stem catarrhine Aegyptopithecus (Fig. 4j), characterized by an almost triangular morphology (albeit less so in the last genus). The superiormost portion of the anterior canal bends medially, causing a moderate torsion of the canal trajectory. This morphology is also found in the stem platyrrhine Homunculus (Fig. 4f) and, to a lesser extent, Chlorocebus (Fig. 4l)

and Dolichocebus (Fig. 4e), while in most cercopithecoids it is much more bent (e.g., Macaca; Fig. 4m). A sinuous trajectory of the anterior canal, although with a different morphology, is also displayed by other taxa (e.g., Cebus; Fig. 4i) and thus is not very informative from a phylogenetic viewpoint. Despite the aforementioned similarities,

Epipliopithecus differs from the stem platyrrhines Homunculus (Fig. 4f) and Dolichocebus (Fig. 4e), from most extant platyrrhines (particularly Ateles; Fig. 4g), and from the stem catarrhine Aegyptopithecus (Fig. 4j), in displaying a much less mediolaterally compressed anterior canal.

The posterior canal of Epipliopithecus is slightly taller than wide, similar to that of Alouatta (Fig. 4h) and Symphalangus (Fig. 4p), but differs from the latter by displaying a less arched connection with the CC. The orientation of the posterior canal relative to the plane defined by the anterior canal is different in the two individuals of Epipliopithecus: it forms an obtuse angle in NHMW 1970/1397/0003 (resembling the hylobatid condition), but forms a right angle in NMB OE 303 (as in other anthropoids; SOM Fig. S2).

The lateral canal is rounded and smaller than the other canals (more so in NMB OE 303), as in stem platyrrhines (Fig. 4e,f) and the stem catarrhine Aegyptopithecus (Fig. 4j), although in Epipliopithecus this canal is not strongly compressed mediolaterally as in the latter taxon (Fig. 4j). The trajectory of the ampullary portion of the lateral canal slightly bends superiorly (more so in NMB OE 303; Fig. 4b,c), while the insertion of its slender part is located anteriorly to the base of the CC (particularly in NHMW 1970/1397/0003; Fig. 4a), so that-as in extant hominoids but unlike cercopithecoids-the lateral canal does not intersect the plane defined by the posterior canal. The lateral canal also shows a wave-like shape, with its lateral-most tip pointing downwards, superficially resembling some individuals of Pongo (Fig. 4r), while differing from the morphology of Trachypithecus (Fig. 4k) and Macaca (Fig. 4m), where the canal bends inferiorly right before the ampullary portion.

Shape analysis

The bgPCA discriminates major anthropoid clades with just minimal overlap when the three axes are considered simultaneously (Fig. 6), thus closely resembling the previous results by [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF] despite the increased number of platyrrhine taxa included here. The bgPCA results reported in Figure 6 closely resemble those derived using a cross-validated bgPCA (SOM Fig. S1), indicating that group separation is not spurious [START_REF] Cardini | Cross-validated between-group PCA scatterplots: A solution to spurious group separation?[END_REF].

The first principal component (bgPC1, which explains 59% of the variance) mainly reflects differences in volumetric proportions among the SCs and the volume they occupy relative to that of the bony vestibule, separating hominids (stout canals; quite negative scores) from both cercopithecoids and hylobatids (slender canals; positive to slightly negative scores), while platyrrhines (including stem taxa), the stem anthropoid Parapithecus, the stem catarrhine Aegyptopithecus, the stem hominoid Oreopithecus, and

Epipliopithecus occupy an intermediate position in the morphospace. In particular, the two Epipliopithecus individuals, due to their fairly slender canals (Fig. 4a-c), display similar intermediate scores along this axis, overlapping extensively with both extant and extinct platyrrhines in the overlap zone of cercopithecoids and hominoids (Fig. 6a,c).

In turn, bgPC2 (which explains 30% of the variance) accounts for differences in the size and shape of the anterior and posterior canals (Fig. 6a,d The slightly dissimilar bgPC3 scores for the two Epipliopithecus individuals result from differences in orientation between the posterior and anterior canals (obtuse angle in NHMW 1970/1397/0003 vs. right angle in NMB OE 303; SOM Fig. S2), causing a wider separation between the lateral and posterior canals (Fig. 4a-c).

When the three bgPCs are considered together, the two Epipliopithecus individuals

show the greatest morphological similarities with platyrrhines (less so in NHMW 1970/1397/0003), as demonstrated by Mahalanobis distances from group centroids and by their posterior probabilities of group membership ( 5). A cluster analysis based on the momenta of the deformation fields confirms these results (Fig. 7).

Epipliopithecus clusters with Alouatta and Ateles (large and rounded vertical canals and a large gap between the lateral and posterior canals), as well as Pithecia (obtuse angle formed by the anterior and posterior canals), within a larger cluster that includes the remaining extant platyrrhines and the other fossil taxa included in the analysis. In particular, Aegyptopithecus and Homunculus cluster with Saimiri and Cebus (flat lateral canal and similarities in the anterior canal morphology), while Oreopithecus clusters with larger group that also includes most cercopithecoids, and extant great apes cluster together due to their distinctive stout volumetric proportions [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF].

Phylogenetic signal and phylomorphospace

Like previous analyses [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF][START_REF] Del Rio | Allometry, function and shape diversification in the inner ear of platyrrhine primates[END_REF]Morimoto, et al., 2020, our results indicate that the vestibule and SCs embed significant phylogenetic signal (K mult = 1.134, p < 0.001), suggesting these traits conform to a Brownian motion model of evolution, with closely related taxa resembling one another slightly more than expected (K mult > 1). The phylogenetic signal computed for each bgPC separately is significant in all instances (Table 6), with bgPC1 and bgPC2 suggesting the same evolutionary mode as K mult (K > 1). Conversely, we observe that the variance accumulates within clades for bgPC3 (K < 1), thus suggesting that changes along this axis might be more strongly affected by homoplasy.

The phylogenetic signal detected justifies the application of the phylomorphospace approach (Fig. 8). The results indicate that the reconstructed LCAs of crown anthropoids (Fig. 9a) and crown catarrhines (Fig. 9c) fall within the variability of extant New World monkeys, being very close to the platyrrhine LCA (Fig. 9b)-irrespective of the phylogenetic hypothesis used in the analysis for Epipliopithecus (i.e., stem catarrhine vs.

stem hominoid, Figs. 3 and8; SOM Fig. S3). Cercopithecoids and hominoids appear much more derived in SC morphology than platyrrhines, but in different directions. The crown anthropoid, crown platyrrhine and crown catarrhine LCAs are reconstructed as possessing large and slightly vertically-elongated canals (more so in the crown anthropoid and crown platyrrhine LCAs; Fig. 9a,b) coupled with a long CC (shorter in the crown catarrhine LCA; Fig. 9c), intermediate volumetric proportions (similar to those found in New World monkeys and cercopithecins; Fig. 10), and a coplanar lateral canal that does not intersect the plane of the posterior one (Fig. 9a-c). The LCA of crown catarrhines also shows a slightly more superiorly bent ampullary portion, more so than in Epipliopithecus (Fig. 9c). In contrast, the reconstructed crown hominoid LCA (Fig. 9d) is found in an area of the morphospace devoid of extant taxa and, according to our estimation, it already displayed some derived characters that are not found in Epipliopithecus (i.e., moderately vertically-compressed anterior canal, stouter canal proportions, lateral ampulla connecting more superiorly with the vestibule).

From a phenetic viewpoint, based on weighted Euclidean distances between

Epipliopithecus and the bgPC scores for the reconstructed LCAs (Table 7), the former taxon is most similar to the crown catarrhine ancestral condition, and also closer to the crown anthropoid and platyrrhine LCAs, than to the ancestral conditions reconstructed for either hominoids or cercopithecoids.

We further synthesized the information provided by the phylomorphospace approach by defining seven discrete characters coded in a cladistic fashion (Table 8; Fig. 11). Their coding for the reconstructed LCAs as well as both extant and extinct anthropoids included in the analyses is reported in Table 9 and SOM Table S4. When the character states for extinct and extant taxa are analyzed against the two phylogenetic hypotheses by considering parsimony as a criterion (Table 10), Epipliopithecus is more parsimoniously interpreted as a stem catarrhine (Fig. 3a) than as a stem hominoid (Fig. 3b). The phylogenetic implications of the seven coded characters (Fig. 11; Tables 8 and9;

SOM Table S4) are discussed below and illustrated in Figure 12.

Size of the vestibule relative to the semicircular canals Extant hominids differ from all the remaining extant taxa in possessing a relatively larger vestibule, which may be thus interpreted as a synapomorphy of at least crown hominids. Among the extinct taxa, only the purported stem hominoid Oreopithecus displays the derived hominid condition, indicating either an independent acquisition of this feature in this taxon (as supported by our LCA reconstructions) or a secondary reversal in hylobatids. Epipliopithecus, in any case, retains the plesiomorphic condition of nonhominoid anthropoids.

Robusticity of the semicircular canals This character has the same distribution as the size of the vestibule relative to the SCs. Extant hominids and Oreopithecus differ from the remaining taxa by displaying stouter proportions. Accordingly, such proportions might be interpreted either as convergent between Oreopithecus and hominids, or as a hominoid synapomorphy with subsequent reversal in hylobatids. Our LCA reconstructions do not provide clear support for either possibility, as they suggest an intermediate ancestral condition in the overlap zone between hominoids and nonhominoid catarrhines. In either case, for this character Epipliopithecus displays the more plesiomorphic condition of nonhominoid anthropoids.

Shape of the anterior semicircular canal This character is more variable than the preceding ones, both within anthropoid subclades, and sometimes even within the same species. However, extant catarrhines generally differ from platyrrhines by possessing an anterior canal that is not superiorly elongated, being instead either rounded (as in humans and most cercopithecoids) or vertically compressed (as in great apes and generally hylobatids, although in the latter it varies intraspecifically between rounded and vertically compressed). Our LCA reconstructions suggest that the ancestral anthropoid condition-a superiorly elongated anterior canal-is symplesiomorphic not only for platyrrhines but also for the stem catarrhine Aegyptopithecus. They further support the view that a rounded anterior SC is synapomorphic of crown catarrhines, while a vertically compressed anterior SC would be synapomorphic for crown hominoids + Oreopithecus. In this regard,

Epipliopithecus is more derived than Aegyptopithecus but less so than Oreopithecus. This character, therefore, unambiguously supports for Epipliopithecus a catarrhine status more derived than in Aegyptopithecus, although it would be consistent with either a stem catarrhine or a stem hominoid status.

Shape of the anterior portion of the semicircular canal Hylobatids and orangutans differ from the rest of the sample by displaying an anterosuperiorly-projecting anterior portion of the anterior canal. This condition may be interpreted as a crown hominoid synapomorphy subsequently reversed in hominines, as further supported by the fact that Oreopithecus displays the derived condition for hominoids. Alternatively, this feature might have been independently acquired in Oreopithecus, as suggested by our LCA reconstructions, which only recover it as a hylobatid synapomorphy. Given the possession of other SC hominoid synapomorphies in Oreopithecus, we tend to favor the former interpretation, even if both are equally parsimonious. In any case, Epipliopithecus retains the more plesiomorphic condition of non-hominoid anthropoids.

Shape of the posterior semicircular canal Although this character is somewhat variable within anthropoid subclades and sometimes even within species, some generalities can be drawn. In platyrrhines, the posterior canal is generally elongated superiorly to some extent, whereas most cercopithecoids have a rounded posterior canal, and hominoids generally vary between a rounded and a vertically compressed morphology (only sometimes superiorly elongated in Pan). Our LCA reconstructions indicate that platyrrhines and Aegyptopithecus retain the ancestral anthropoid condition (superiorly elongated posterior canal), whereas the rounded morphology would be synapomorphic for crown hominoids.

Epipliopithecus displays the plesiomorphic anthropoid condition and thus differs from

Oreopithecus, which displays the derived catarrhine morphology.

Shape of the lateral semicircular canal ampullary portion Extant hominoids differ from the remaining extant taxa and all the analyzed extinct genera by displaying a markedly superiorly-bent ampullary portion of the lateral canal. Both Epipliopithecus and

Oreopithecus thus display a more plesiomorphic condition than crown hominoids, as further confirmed by our LCA reconstructions.

Length of the common crus This character is also variable to some extent, but platyrrhines generally display a longer CC than extant catarrhines, with hominoids having an even shorter CC than most cercopithecoids. Our LCA reconstructions support an intermediate length of the CC as synapomorphic of crown catarrhines, with a short CC being synapomorphic for hominoids. Epipliopithecus resembles Aegyptopithecus and platyrrhines by retaining the ancestral anthropoid condition, whereas Oreopithecus displays the derived hominoid morphology.

Discussion

Our analysis of the SC and vestibule morphology of Epipliopithecus allows us to refine our understanding of the evolution of this anatomical region in anthropoid primates and to refine previous hypotheses proposed by [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF]. The results of our deformation-based 3DGM analysis and the reconstruction of ancestral morphotypes for main anthropoid clades indicate that, like the stem catarrhine Aegyptopithecus, Epipliopithecus displays a platyrrhine-like morphology most similar to that reconstructed for the crown catarrhine LCA. This might be compatible with Epipliopithecus being either a stem catarrhine, or a crown catarrhine only slightly postdating the cercopithecoid-hominoid split. However, the fact that Epipliopithecus most closely resembles the crown anthropoid (and platyrrhine) LCAs (Table 7) suggests that the semicircular morphology of this taxon is most consistent with its status as a stem catarrhine. This conclusion is further supported by the analysis of seven discrete characters coded for this anatomical area-which indicate that this is the most parsimonious hypothesis, for reasons discussed in greater detail below.

Epipliopithecus as a hominoid

Based on the morphology of the SCs and vestibule, Epipliopithecus lacks multiple hominoid synapomorphies, including a large vestibule relative to the canals, stout SCs, vertically-compressed anterior canal, anterosuperiorly-projecting anterior portion of the anterior canal, markedly superiorly-bent ampullary portion of the lateral canal, and short CC. [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF] already interpreted some of these features (vertically-compressed anterior canal and markedly superiorly-bent ampullary portion of the lateral canal) as potential crown hominoid synapomorphies, whereas they interpreted others (large vestibule and stout canals) as hominid synapomorphies. Urciuoli et al. ( 2020) interpreted a superiorly-bent ampullary portion of the lateral canal as a hominoid synapomorphy.

However, hominoids are, in fact, characterized by the possession of a markedly bent trajectory, whereas other catarrhines display a flat to slightly superiorly-bent ampullary portion of the lateral canal. This is the case for Epipliopithecus, which displays much less bending of the lateral canal than in Oreopithecus or any extant hominoid.

The possession of a large vestibule and stout canals was previously interpreted as being synapomorphic for hominids [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF] because hylobatids display a different ('monkey-like') condition. The differences in volumetric proportions between

Epipliopithecus and hominids are particularly clear (Fig. 10), with the former closely resembling platyrrhines, Aegyptopithecus, and the inferred ancestral catarrhine condition.

Given that both features are present in Oreopithecus, they may be interpreted as hominoid synapomorphies subsequently reversed in hylobatids-thereby supporting a more basal branching for Epipliopithecus. However, their interpretation as hominid synapomorphies is equally parsimonious, as it would only imply their independent acquisition in Oreopithecus.

Therefore, neither a large vestibule nor stout canals can be used to unambiguously discount a hominoid status for Epipliopithecus. A similar caveat applies to the lack of an anterosuperiorly-projecting anterior canal in Epipliopithecus. This condition was previously interpreted as an autapomorphy of Hylobates (Le [START_REF] Maître | New data about semicircular canal morphology and locomotion in modern hominoids[END_REF] or as a hylobatid synapomorphy [START_REF] Spoor | Comparative review of the human bony labyrinth[END_REF][START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF]). However, given its presence in orangutans and Oreopithecus, it is more readily interpreted as a hominoid synapomorphy subsequently reversed in hominines. The interpretation of some of the potential hominoid synapomorphies lacking in Epipliopithecus is ambiguous due to homoplasy (convergence and/or reversal). However, it is worth noting that, except for the markedly superiorly bent ampullary portion of the lateral canal, Oreopithecus further displays two more unambiguous hominoid synapomorphies (vertically compressed anterior canal and short CC). The absence of these features in Epipliopithecus thus conclusively excludes a more derived hominoid status for the latter as compared with Oreopithecus.

Epipliopithecus also displays some hylobatid-like features in the spatial configuration between the lateral and posterior canals, as well as in the orientation between the anterior and posterior canals. According to [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF], the lack of intersection between the lateral and posterior canals and the presence of an obtuse angle between the anterior and posterior canals would be synapomorphic for hominoids and hylobatids, respectively. However, only Hylobates consistently displays both features, while most anthropoid taxa, as well as the two Epipliopithecus individuals, show a considerable amount of intraspecific variation. Hence, we refrained from coding these features in a cladistic manner, especially in view of the low phylogenetic signal (K < 1) recovered for bgPC3 (accounting for the variation in the configuration of these features), which suggests a substantial degree of homoplasy. Indeed, previous analyses hypothesized that suspensory species possess more obtuse angles between the vertical canals [START_REF] Gonzales | Intraspecific variation in semicircular canal morphology-A missing element in adaptive scenarios?[END_REF], as this configuration provides an increased sensitivity for pitch (at the expense of roll) head movements (Muller and Verhagen, 2002a,b,c). The similarities between NHMW 1970/1397/0003, hylobatids, and some atelids [START_REF] Spoor | Comparative review of the human bony labyrinth[END_REF][START_REF] Gonzales | Intraspecific variation in semicircular canal morphology-A missing element in adaptive scenarios?[END_REF] would thus agree with previous inferences about the locomotor repertoire of this taxon including some degree of suspensory behaviors [START_REF] Zapfe | The skeleton of Pliopithecus (Epipliopithecus) vindobonensis Zapfe and Hürzeler[END_REF][START_REF] Fleagle | Locomotor adaptations of Oligocene and Miocene hominoids and their phyletic implications[END_REF][START_REF] Langdon | Functional morphology of the Miocene hominoid foot[END_REF][START_REF] Rose | Quadrupedalism in some Miocene catarrhines[END_REF][START_REF] Arias-Martorell | Morphological affinities of the proximal humerus of Epipliopithecus vindobonensis and Pliopithecus antiquus: Suspensory inferences based on a 3D geometric morphometrics approach[END_REF]. In contrast, the more plesiomorphic condition of NBM OE 303III (characterized by tangent lateral and posterior canals, and vertical canals approximating a right angle), also found in Aegyptopithecus and some nonsuspensory platyrrhine species, suggests caution when using SC orientation alone for inferring positional behaviors [START_REF] Perier | Different level of intraspecific variation of the bony labyrinth morphology in slow-versus fast-moving Primates[END_REF]contra Malinzak et al., 2012;[START_REF] Berlin | Functional implications of ubiquitous semicircular canal non-orthogonality in mammals[END_REF].

Epipliopithecus as a stem catarrhine

Epipliopithecus resembles both stem platyrrhines and the stem catarrhine

Aegyptopithecus in lacking all of the aforementioned hominoid synapomorphies, thereby retaining the plesiomorphic anthropoid condition-a relatively small vestibule, slender SCs, anterosuperiorly nonprojecting anterior portion of the anterior canal, superiorly elongated posterior canal, ampullary portion of the lateral canal not markedly bent superiorly, and long CC. The fact that Epipliopithecus lacks hominoid synapomorphies displayed by Oreopithecus could still be consistent with a more basal stem hominoid status. However, such an interpretation is contradicted by the retention in Epipliopithecus of a superiorly elongated posterior canal and a long CC-contrasting with the rounded posterior canal and moderately short CC that are synapomorphic of crown catarrhines. The catarrhine status of Epipliopithecus and other pliopithecoids is well established based on multiple features, such as the loss of the second premolars and the presence of a C 1 /P 3 honing complex (e.g., [START_REF] Harrison | Catarrhine origins[END_REF]. The catarrhine status of Epipliopithecus is further supported by the possession of a rounded anterior canal, which is intermediate between the primitive morphology (superiorly elongated anterior canal) retained by platyrrhines and Aegyptopithecus, and the more derived (vertically compressed) morphology synapomorphic of hominoids. In this regard, Epipliopithecus is more derived toward crown catarrhines than the propliopipithecoid Aegyptopithecus, in agreement with other cranial features such as the possession of a partially enclosed tubular ectotympanic in Epipliopithecus (e.g., [START_REF] Harrison | Catarrhine origins[END_REF].

In summary, based on the morphology of the SCs and vestibule, Epipliopithecus is most parsimoniously interpreted as a stem catarrhine more derived than Aegyptopithecus, due to its possession of a crown catarrhine synapomorphy-rounded anterior canalcoupled with the lack of two additional crown catarrhine synapomorphies (superiorly elongated posterior canal and long CC) and multiple hominoid and/or hominid synapomorphies as described above. The shapes of the anterior and posterior canals and CC should be considered with caution in light of the intraspecific variability displayed by these characters in some taxa (SOM Table S4). Previous analyses noted a structural relationship between the morphology of these canals and the extension of the subarcuate fossa [START_REF] Jeffery | The primate subarcuate fossa and its relationship to the semicircular canals part I: prenatal growth[END_REF][START_REF] Jeffery | The primate subarcuate fossa and its relationship to the semicircular canals part II: Adult interspecific variation[END_REF], and this relationship has been uncritically assumed in some studies [START_REF] Spoor | The primate semicircular canal system and locomotion[END_REF][START_REF] Silcox | Semicircular canal system in early primates[END_REF][START_REF] Gonzales | Intraspecific variation in semicircular canal morphology-A missing element in adaptive scenarios?[END_REF]. However, in most cases the fossa simply expands within the space left available from the ossification of the canals, with little or no influence on their shape [START_REF] Jeffery | The primate subarcuate fossa and its relationship to the semicircular canals part II: Adult interspecific variation[END_REF]; see also [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF]. In support of the latter hypothesis, we observe meager dissimilarities in the anterior canal morphology of NHMW 1970/1397/0003 and NBM OE 303III-except for the angle, as discussed above-irrespective of the marked differences in the morphology of the fossa between the two individuals (Zapfe, 1960).

While a large amount of morphological variation has been documented within ruminant genera (Mennecart and Costeur, 2016), variation in CC length and shape has not been exhaustively analyzed in primates [START_REF] Spoor | Comparative review of the human bony labyrinth[END_REF][START_REF] Ekdale | Comparative anatomy of the bony labyrinth (inner ear) of placental mammals[END_REF][START_REF] Lee | A morphometric study of the semicircular canals using micro-CT images in three-dimensional reconstruction[END_REF]. In the present study, we found considerable intraspecific variation in CC length for some species of monkeys and apes. Nevertheless, our results support a clear morphocline from the ancestral condition (long CC) retained by platyrrhines, Aegyptopithecus, and Epipliopithecus, to the most derived condition (short CC) characteristic of hominoids, with cercopithecoids displaying an intermediate condition that is likely synapomorphic for crown catarrhines as a whole. Therefore, Epipliopithecus SC morphology supports its interpretation as more derived than Aegyptopithecus toward crown catarrhines, but excludes a crown catarrhine status and, in particular, a closer relationship with hominoids (unlike in the case of Oreopithecus).

Conclusions

Our results are in broad agreement with previous analyses suggesting that Epipliopithecus displays a 'typical monkey' inner ear morphology [START_REF] Morimoto | Variation of bony labyrinthine morphology in Mio-Plio-Pleistocene and modern anthropoids[END_REF], while Oreopithecus possesses SC and vestibule features derived toward the crown hominoid condition [START_REF] Urciuoli | The evolution of the vestibular apparatus in apes and humans[END_REF]. At the same time, our study further refines previous comparisons of SC and vestibule morphology between Epipliopithecus and other anthropoids, enabling us to test competing hypotheses about the phylogenetic position of this taxon (i.e., stem catarrhine vs. stem hominoid).

From a phenetic viewpoint, for this anatomical area Epipliopithecus more closely resembles platyrrhines and the stem catarrhine Aegyptopithecus, as well as the reconstructed ancestral catarrhine morphotype. The fact that Epipliopithecus shows greater similarities with the platyrrhine and anthropoid ancestral morphotypes, rather than with those of cercopithecoids or hominoids, supports the view that Epipliopithecus is a stem catarrhine instead of a stem hominoid. From a cladistic perspective, this interpretation is confirmed based on a series of crown catarrhine and crown hominoid synapomorphies. Epipliopithecus is more parsimoniously interpreted as a stem catarrhine than as a stem hominoid based on the vestibular morphology analyzed here because it lacks several catarrhine and all hominoid synapomorphies. Specifically, the possession of a rounded posterior canal reinforces the view that Epipliopithecus is more derived than

Aegyptopithecus among stem catarrhines.

The information provided by the SCs and vestibule is thus congruent with the ectotympanic morphology of Epipliopithecus (see review in [START_REF] Fricano | The primate ectotympanic tube: correlates of structure, function, and development[END_REF], which is more plesiomorphic than in crown catarrhines but more derived than in propliopithecoids. Some similarities between Epipliopithecus and hylobatids are based on characters that are too variable within species to be of use for phylogenetic assessment. Such features might have evolved independently between some atelids and hylobatids, due to similar locomotor-related selection pressures, and do not support the close phylogenetic link classically hypothesized between pliopithecoids and hylobatids [START_REF] Hürzeler | Contribution a l'odontologie et a la phylogénèse du genre Pliopithecus Gervais[END_REF]Zapfe, 1960[START_REF] Zapfe | Die Primatenfunde aus der miozänen Spaltenfüllung von Neudorf an der March (Děvínská Nová Ves)[END_REF][START_REF] Simons | The history of extinct gibbon-like primates[END_REF], particularly given that Epipliopithecus displays no crown hominoid synapomorphies. We therefore conclude that the SC and vestibular morphology reinforces the most commonly held view that, in accordance with most [START_REF] Zalmout | New Oligocene primate from Saudi Arabia and the divergence of apes and Old World monkeys[END_REF][START_REF] Stevens | Palaeontological evidence for an Oligocene divergence between Old World monkeys and apes[END_REF][START_REF] Nengo | New infant cranium from the African Miocene sheds light on ape evolution[END_REF] but not all [START_REF] Alba | Miocene small-bodied ape from Eurasia sheds light on hominoid evolution[END_REF] recent cladistic analyses, Epipliopithecus is best interpreted as a stem catarrhine rather than a stem hominoid.

(

Oreopithecus bambolii

1 1 0 1 1 0 Parapithecus grangeri 0 0 2 0 2 0 Crown anthropoid LCA 0 0 2 0 2 0 Crown platyrrhine LCA 0 0 2 0 2 0 Crown catarrhine LCA 0 0 1 0 1 0 Crown cercopithecoid LCA 0 0 1 0 1 0 Crown hominoid LCA 0 0 0 0 1 1 Crown hylobatid LCA 0 0 0 1 1 1 Crown hominid LCA 1 1 0 0 1 1 a 1133
See character definitions in Table 7 and SOM Table S2 for the coding of extant species. 1134 hypotheses (i.e., stem catarrhine vs. stem hominoid) discussed in this paper for Epipliopithecus. The higher the index, the more parsimonious the hypothesis. a .

Metrics

Stem catarrhine (Fig. 3a) Stem hominoid (Fig. 3b) 8 and9, and SOM Table S4.

  : NMB OE 303a, b (individual III), left (a) and right (b), housed in the Naturhistorisches Museum of Basel, Switzerland 2 ; and NHMW 1970/1397/0003 (individual II), right, housed in the Naturhistorisches Museum of Wien, Austria.

  ), in the position of the lateral canal ampullary insertion on the vestibule, and in CC length, separating most platyrrhines (positive scores) from catarrhines (moderately positive to negative scores). In particular, platyrrhines possess large and very superiorly elongated canals in the portion close to the CC apex, as well as a flat lateral canal, which also connects more inferiorly on the vestibule with its ampullary portion. Catarrhines are more variable in these features, showing rounded to vertically compressed anterior and posterior canals, a shorter CC, and a variably sinuous lateral canal with its ampullary portion connecting more superiorly.Epipliopithecus displays moderately positive scores, falling within the range of several extant platyrrhines (Aotus, Alouatta, Callithrix and Callicebus), due to their large anterior and posterior canals, coupled with a long CC and a small lateral canal. Both the stem platyrrhines and Oreopithecus show similar moderately positive scores, while Aegyptopithecus and Parapithecus show markedly positive values due to their superiorly elongated vertical canals (Fig.6a).Finally, bgPC3 (which explains 11% of the variance) is driven by the position of the lateral canal relative to the posterior one, by the size and orientation of the posterior canal, as well as the shape of the anterior canal and CC thickness (Fig.6b, e), separating hylobatids (most positive values) from most extant and fossil anthropoids (intermediate to negative scores). Hylobatids have a much larger gap between the lateral and posterior canals than other anthropoids except some modern humans, and their posterior canal is also smaller than, and forms an obtuse angle with, the large and anteriorly-protruding anterior canal. In contrast, in most cercopithecoids, Aotus, and Callithrix, the lateral canal broadly intersects with the posterior canal, while in the African great apes, Theropithecus, and Cebus the canals are only minimally separated. In addition, in all extant anthropoids except hylobatids, the plane of the posterior canal forms a right angle with the anterior canal, which does not project anteriorly. Both Epipliopithecus individuals display positive scores (NMB OE 303 with lower values), overlapping with some hylobatids (mainly Hoolock) and other extant anthropoids (particularly the hominids Homo and Pongo, the platyrrhines Ateles and Alouatta, and the cercopithecoids Theropithecus and Piliocolobus).

Figure captions Figure 1 .

 captions1 Figure captions

Figure 2 .

 2 Figure 2. Cladogram of extant and fossil anthropoids showing the two phylogenetic

Figure 3 .

 3 Figure 3. Phylogenetic trees used for the phylomorphospace approach. They differ in

Figure 4 .

 4 Figure 4. Rendered 3D models of the semicircular canals and vestibule of Epipliopithecus

Figure 5 .

 5 Figure 5. Bivariate plot of canal log-transformed cube root canal volume (mm; Ln VolSC)

Figure 6 .

 6 Figure 6. Patterns of vestibule and semicircular canal shape variation among major

Figure 7 .

 7 Figure 7. Dendrogram resulting from a cluster analysis (Ward's method) based on

Figure 8 .

 8 Figure 8. Phylomorphospace of the anthropoid semicircular canal. The phylogenetic tree

Figure 9 .

 9 Figure 9. Reconstruction of the semicircular canals and vestibule for the last common

Figure 10 .

 10 Figure 10. Box-and-whisker plot of allometric residuals based on best-fit line of the

Figure 11 .

 11 Figure 11. Illustration of the discrete characters of semicircular canal (SC) and vestibule

  Table 3), leading us to reject close similarities to the remaining groups for NMB OE 303, and to all anthropoid groups for

NHMW 1970/1397/0003 (p < 0.05). Aegyptopithecus, Parapithecus, Oreopithecus, and stem platyrrhines also closely resemble extant New World monkeys, with Oreopithecus also showing marginal affinities with cercopithecoids (Table

3

). We obtain very similar results when considering all catarrhines as a single group, with all fossils being classified as platyrrhines (Table

4

). For Oreopithecus and NHMW 1970/1397/0003, group membership for catarrhines cannot be rejected. However, both specimens show much lower Mahalanobis distances to the platyrrhine centroid (almost three times) than to that of catarrhines. The two Epipliopithecus individuals are closer to one another than they are to other fossil taxa (except for one individual of Homunculus, MPM-PV 3501), in turn showing similarities with stem platyrrhines, Aegyptopithecus and Oreopithecus (Table

Table 1 .

 1 Epipliopithecus NHMW 1970/1397/0003), Martin Dockner, Loïc Costeur (Epipliopithecus NMBOE 303), Lorenzo Rook (Oreopithecus), José Braga (human specimens), Lynn Copes, Lynn Lucas, and the MCZ (part of the scans used in the study, funded by NSF DDIG #0925793 and Wenner-Gren Foundation Dissertation Grant #8102 to Lynn Copes), Richard Kay (Homunculus and Dolichocebus),Timothy Ryan (Aegyptopithecus; funded by NSF BCS-0416164 to Timothy Ryan and the Leakey Foundation), and the Division of Fossil Primates of the Duke Lemur Center (Parapithecus). We also thank Erik Seiffert and Steven Heritage for providing a digital rendering of Parapithecus. Finally, we thank the Editor (Andrea Taylor), the Associate Editor, and three anonymous reviewers for useful comments that helped us to improve a previous version of this paper. Digital object identifiers (DOIs) of the 3D virtual models of the vestibule and semicircular canals of Epipliopithecus vindobonensis available from MorphoSource.org (https://www.morphosource.org).

	Catalog No.	Museum	DOI
	NMBOE 303a (individual III)	NMBOE	https://doi.org/10.17602/M2/M113935
	NMBOE 303b (individual III)	NMBOE	https://doi.org/10.17602/M2/M113933
	NHMW 1970/1397/0003 (individual II)	NHMW	https://doi.org/10.17602/M2/M113932
	Abbreviations: NMB OE = Naturhistorisches Museum Basel, Switzerland; NHMW =
	Naturhistorisches Museum Wien, Austria.

Table 2 .

 2 Log-transformed cube root of canal volume (ln VolSC, mm 3 ) and logtransformed canal length (ln L, mm) measured for the fossil taxa included in the analysis. a See SOM TableS1for the specimens included in the extant comparative sample.

	Catalog No.	Taxon	ln VolSC	ln L
	NMBOE 303a	Epipliopithecus vindobonensis	3.640	0.993
	NMBOE 303b	Epipliopithecus vindobonensis	3.602	0.910
	NHMW 1970/1397/0003	Epipliopithecus vindobonensis	3.593	0.916
	CGM 85785	Aegyptopithecus zeuxis	3.365	0.847
	MPM-PV 30501	Homunculus patagonicus	3.391	0.780
	MPM-PV 30502	Homunculus patagonicus	3.359	0.720
	MPM-PV 30503	Homunculus patagonicus	3.359	0.784
	MACN 14128	Dolichocebus gaimanensis	3.802	0.803
	BAC 208	Oreopithecus bambolii	3.295	0.803
	DPC 18651	Parapithecus grangeri	3.640	0.993
	Abbreviations: BAC = Baccinello (field acronym; housed at Naturhistorisches Museum
	Basel, Switzerland); CGM = Egyptian Geological Museum, Cairo, Egypt; MPM-
	PV = Museo Regional Provincial Padre M.J. Molina, Río Gallegos, Argentina;
	MACN = Museo Argentino de Ciencias Naturales, Buenos Aires, Argentina; DPC = Duke
	Lemur Center, Durham, NC, USA.

a

Table 3 .

 3 Mahalanobis distances (D 2 ) and posterior probabilities of group membership (p) based on the scores for fossil specimens in the between-group principal component analysis for the entire anthropoid sample. a,b

	D 2	Cercopithecoidea Hominidae Hylobatidae Platyrrhini
	Epipliopithecus vindobonensis (NHMW	17.179	10.539	6.485	3.437
	1970/1397/0003)
	Epipliopithecus vindobonensis (NMB OE	12.190	14.262	6.588	0.779
	303a)
	Epipliopithecus vindobonensis (NMB OE	13.307	15.085	6.682	1.056
	303b)
	Oreopithecus bambolii (BAC 208)	8.083	5.450	11.574	1.579
	Aegyptopithecus zeuxis (CGM 85785)	12.430	9.133	15.513	0.990
	Homunculus patagonicus (MPM-PV 3501) 11.817	13.356	11.017	0.073
	Homunculus patagonicus (MPM-PV 3502) 10.336	12.736	12.056	0.165
	Homunculus patagonicus (MPM-PV 3503) 10.083	7.449	11.284	0.590
	Dolichocebus gaimanensis (MACN 14128) 5.204	13.516	12.687	1.935
	Parapithecus grangeri (DPC 18651)	6.533	17.859	13.047	2.110
	P	Cercopithecoidea Hominidae Hylobatidae Platyrrhini
	Epipliopithecus vindobonensis (NHMW	0.006	0.007	0.018	0.029
	1970/1397/0003)
	Epipliopithecus vindobonensis (NMB OE	0.018	<0.001	<0.001	0.678
	303a)
	Epipliopithecus vindobonensis (NMB OE	0.013	<0.001	<0.001	0.608
	303b)
	Oreopithecus bambolii (BAC 208)	0.052	0.005	<0.001	0.530
	Aegyptopithecus zeuxis (CGM 85785)	0.001	<0.001	<0.001	0.688
	Homunculus patagonicus (MPM-PV 3501) 0.003	<0.001	<0.001	0.980
	Homunculus patagonicus (MPM-PV 3502) 0.003	<0.001	<0.001	0.919
	Homunculus patagonicus (MPM-PV 3503) 0.019	0.001	<0.001	0.848

Table 4 .

 4 Mahalanobis distances (D 2 ) and posterior probabilities of group membership (p) based on the scores for fossil specimens in the between-group principal component analysis for the entire anthropoid sample and considering all catarrhines as a single group. a,b

	D 2	Catarrhini	Platyrrhini
	Epipliopithecus vindobonensis (NHMW 1970/1397/0003)	13.016	5.341
	Epipliopithecus vindobonensis (NMB OE 303a)	11.837	1.654
	Epipliopithecus vindobonensis (NMB OE 303b)	13.040	2.098
	Oreopithecus bambolii (BAC 208)	9.085	3.890
	Aegyptopithecus zeuxis (CGM 85785)	16.900	3.204
	Homunculus patagonicus (MPM-PV 3501)	13.814	0.135
	Homunculus patagonicus (MPM-PV 3502)	13.057	0.284
	Homunculus patagonicus (MPM-PV 3503)	10.989	1.806
	Dolichocebus gaimanensis (MACN 14128)	8.645	2.417
	Parapithecus grangeri (DPC 18651)	12.592	3.670
	P	Catarrhini	Platyrrhini
	Epipliopithecus vindobonensis (NHMW 1970/1397/0003)	0.109	0.241
	Epipliopithecus vindobonensis (NMB OE 303a)	0.022	0.876
	Epipliopithecus vindobonensis (NMB OE 303b)	0.017	0.847
	Oreopithecus bambolii (BAC 208)	0.124	0.673
	Aegyptopithecus zeuxis (CGM 85785)	0.002	0.886
	Homunculus patagonicus (MPM-PV 3501)	0.002	0.985
	Homunculus patagonicus (MPM-PV 3502)	0.002	0.968
	Homunculus patagonicus (MPM-PV 3503)	0.034	0.935
	Dolichocebus gaimanensis (MACN 14128)	0.013	0.841
	Parapithecus grangeri (DPC 18651)	0.002	0.795

Table 5 .

 5 Mahalanobis distances (D 2 ) between specimens of Epipliopithecus and other fossils based on between group principal component analysis scores.

	D 2	NHMW	NMB OE	NMB OE
		1970/1397/0003	303a	303b
	Epipliopithecus vindobonensis (NHMW	-	1.332	1.285
	1970/1397/0003)
	Epipliopithecus vindobonensis (NMB OE 303a)	1.332	-	0.176
	Epipliopithecus vindobonensis (NMB OE 303b)	1.285	0.176	-
	Oreopithecus bambolii (BAC 208)	2.244	1.901	2.055
	Aegyptopithecus zeuxis (CGM 85785)	2.360	1.804	1.927
	Homunculus patagonicus (MPM-PV 3501)	1.943	0.919	1.033
	Homunculus patagonicus (MPM-PV 3502)	2.246	1.251	1.388
	Homunculus patagonicus (MPM-PV 3503)	1.914	1.450	1.592
	Dolichocebus gaimanensis (MACN 14128)	3.081	2.077	2.243
	Parapithecus grangeri (DPC18651)	3.201	2.017	2.161

Abbreviations: NHMW = Naturhistorisches Museum Wien, Austria; NMB OE = Naturhistorisches Museum Basel, Switzerland; BAC = Baccinello (housed at NMB); CGM = Egyptian Geological Museum, Cairo, Egypt; MPM-PV = Museo Regional Provincial Padre M.J. Molina, Río Gallegos, Argentina; MACN = Museo Argentino de Ciencias Naturales, Buenos Aires, Argentina; DPC = Duke Lemur Center, Durham, NC, USA.

Table 6 .

 6 Phylogenetic signal computed for the between-group principal analysis applied to the deformation fields of the extant anthropoid comparative sample. The variance explained by each principal component (bgPC) and the p-value for the statistics are given within parentheses.

		bgPC1 (59%)	bgPC2 (30%)	bgPC3 (11%)
	Pagel's λ	1.000 (p < 0.0001)	0.843 (p < 0.0001)	0.925 (p < 0.0001)
	Blomberg's K	1.148 (p < 0.0001)	1.446 (p < 0.001)	0.732 (p < 0.001)

[START_REF] Morimoto | Variation of bony labyrinthine morphology in Mio-Plio-Pleistocene and modern anthropoids[END_REF] included the bony labyrinth of NMB OE

303a in their comparative study but did not depict or specifically describe its morphology.

Acknowledgements

This research has been funded by the Agencia Estatal de Investigación (CGL2016-76431-P and CGL2017-82654-P, AEI/FEDER EU; and BES-2015-071318 to A.U.), the Generalitat de Catalunya (CERCA Programme, and consolidated research groups 2017 SGR 86 and 2017 SGR 116 GRC), the French Centre National de la Recherche Scientifique, the Leakey Foundation (research grant), and the Synthesys Project (AT-TAF-4689; http://synthesys3.myspecies.info/), which is financed by the European Community Research Infrastructure Action under the FP7. Part of the analyses were performed using High Performance Computing resources from BSC (BCV-2020-1-0008). We are grateful to Jose Torres for the technical help provided in the setup of the analysis. We thank the following people for providing or permitting access to CT scans: Ursula Göhlich

Note that these are probability estimates of having a particular score given membership in a particular group, not the likelihood of group membership in each of the a priori defined groups given a particular score (the greater the number, the higher the probability). Note that these are probability estimates of having a particular score given membership in a particular group, not the likelihood of group membership in each of the a priori defined groups given a particular score (the greater the number, the higher the probability).

b

The lowest distance and highest probability for each specimen are bolded.

Character statements (characters + character states) a

#1 Size of the vestibule relative to the SCs: 0 = small; 1 = large. See Figure 11 for an illustration of the various character states and Table 9 and SOM Table S4 for the scoring of reconstructed last common ancestors and individual taxa, respectively.