Laurent Pallas

Guillaume Daver

Hassane T Mackaye

Andossa Likius

Patrick Vignaud

Franck Guy
email: franck.guy@univ-poitiers.fr

A window into the early evolutionary history of Cercopithecidae: Late Miocene evidence from Chad, Central Africa

Keywords: Cercopithecoides, Colobinae, stem Colobini, Adaptive Radiation, Ecomorphology

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Introduction

With an extensive geographical distribution, a rich taxonomy and a marked ecomorphological diversity, extant Cercopithecidae (i.e., Colobinae and Cercopithecinae) represent one of the most successful adaptive radiations of Neogene primates on the African and Eurasian continents. Old World Monkeys (OWM) are known to diverge from an ancestral African stock (i.e., Victoriapithecidae) presenting dentognathic and postcranial morphologies adaptively linked to frugivory and terrestrial locomotion [START_REF] Harrison | New postcranial remains of Victoriapithecus from the middle Miocene of Kenya[END_REF][START_REF] Benefit | The permanent dentition and phylogenetic position of Victoriapithecus from Maboko Island, Kenya[END_REF]. Extant African (i.e., Colobini) and Asian (i.e., Presbytini) representatives of the subfamily Colobinae depart from this adaptive zone in exhibiting morphological and physiological adaptations associated with folivory and arboreal locomotion. While a rich Miocene OWM fossil record is documented in Eurasia at 8.5-6 Ma with the radiation of the putative stem colobine Mesopithecus spp. [START_REF] Delson | Fossil colobine monkeys of the circum-Mediterranean region and the evolutionary history of the Cercopithecidae (Primates, Mammalia)[END_REF], the fossil record of Miocene OWM in Africa is sparse. Dating back as far as 12.5 Ma, the African cercopithecid fossil record is known from only a handful of localities mostly restricted to East [START_REF] Benefit | Miocene fossil Cercopithecoids from Kenya[END_REF][START_REF] Leakey | Cercopithecidae from Lothagam[END_REF][START_REF] Hlusko | A new Late Miocene species of Paracolobus and other Cercopithecoidea (Mammalia: Primates) fossils from Lemudong'o, Kenya. Kirtlandia[END_REF][START_REF] Frost | Cercopithecidae[END_REF][START_REF] Gilbert | Miocene Cercopithecoidea from the Tugen Hills, Kenya[END_REF][START_REF] Nakatsukasa | Earliest colobine skeletons from Nakali, Kenya[END_REF][START_REF] Suwa | Newly discovered cercopithecid, equid and other mammalian fossils from the Chorora Formation, Ethiopia[END_REF] and North Africa [START_REF] Delson | Fossil colobine monkeys of the circum-Mediterranean region and the evolutionary history of the Cercopithecidae (Primates, Mammalia)[END_REF][START_REF] Benefit | New Fossil Cercopithecoids from the Late Miocene of As Sahabi, Libya[END_REF]. In spite of being suggested as a cradle of diversity for extant Cercopithecidae [START_REF] Böhm | Historical biogeography and the evolution of the latitudinal gradient of species richness in the Papionini (Primata: Cercopithecidae): Evolution of diversity gradients[END_REF]Ting, 2008), Central Africa has provided little evidence of the early evolutionary history of OWM [START_REF] Gundling | Geological context of fossil Cercopithecoidea from eastern Africa[END_REF]. The Central African hominin-bearing fossiliferous area of Toros-Menalla (TM), Chad at ca. 7 ± 0.2 Ma [START_REF] Brunet | A new hominid from the Upper Miocene of Chad, Central Africa[END_REF][START_REF] Lebatard | Application of the authigenic 10Be/9Be dating method to continental sediments: Reconstruction of the Mio-Pleistocene sedimentary sequence in the early hominid fossiliferous areas of the northern Chad Basin[END_REF] has yielded colobine remains, giving us the unique opportunity to assess current hypotheses regarding the paleobiology and phylogenetic relationships of Late Miocene colobines in Africa. Particularly, the wellpreserved dentognathic materials from TM fill a temporal gap between a primitive dental morphology related to frugivory [START_REF] Benefit | New Fossil Cercopithecoids from the Late Miocene of As Sahabi, Libya[END_REF][START_REF] Merceron | Folivory or fruit/seed predation for Mesopithecus, an earliest colobine from the late Miocene of Eurasia?[END_REF][START_REF] Rossie | Early cercopithecid monkeys from the Tugen Hills, Kenya[END_REF][START_REF] Suwa | Newly discovered cercopithecid, equid and other mammalian fossils from the Chorora Formation, Ethiopia[END_REF]Thiery et al., 2017) and a derived dental morphology linked to a leaf-dominated diet [START_REF] Gilbert | Miocene Cercopithecoidea from the Tugen Hills, Kenya[END_REF].

Moreover, the discovery of a nearly complete forelimb allows us to reconsider the emergence of terrestrial locomotor behavior among Miocene colobines [START_REF] Leakey | Cercopithecidae from Lothagam[END_REF]Youlatos et al., 2012). In addition, the chronological setting of TM encompassed the estimated divergence times of extant crown Colobini taxa (Ting, 2008), permitting to assess hypotheses regarding the placement of the Chadian colobine among the stem or crown Colobini group [START_REF] Jablonski | Cercopithecoidea[END_REF][START_REF] Frost | The Hand of Cercopithecoides williamsi (Mammalia, Primates): Earliestevidence for thumb reduction among Colobine monkeys[END_REF]. Here we describe Cercopithecoides bruneti sp. nov. from the Late Miocene of Central Africa, at ca. 7 Ma and provide new evidence for terrestrial locomotor habits and an increase in leaf consumption among Miocene colobines.

We also provide insights into the phylogenetic affinities of the Chadian colobine, and discuss the contribution of TM to our understanding of cercopithecid evolution in light of the ecomorphological diversity of Late Miocene OWM in a previously unknown spatial and temporal setting.

Materials and methods

Material availability and imaging

All the materials described here have been collected between 2000 and 2003 by the Mission Paléoanthropologique Franco-Tchadienne (P.I. Michel Brunet) and are currently curated at the Service de Valorisation des Collections de Paléontologie (CNRD de N'Djamena). Apart from glue consolidation, the fossil material was not subjected to any modification. All the fossil material described here has been scanned at the Université de Poitiers, France. An Easy Tom XL duo µCTscanner yielded virtual image stacks of the Chadian fossil material with resolutions ranging from 21.5µ to 45.6µ. Virtual reconstruction and visualization were obtained with the software Avizo Standard Edition.

Comparative sample

Qualitative and quantitative data for Cercopithecoides williamsi were gathered from µ-CT scan data provided by the Ditsong National Museum of Natural History (Plio-Pleistocene Section).

Qualitative and quantitative date for all other early African colobines derived from the literature. Qualitative and quantitative data for the dentognathic fossil material of early Eurasian Colobinae (i.e., Mesopithecus ssp.) were gathered from µ-CT scans data of high quality dental casts provided by Dr. Gildas Merceron. Mesopithecus pentelicus postcranial data were taken directly from specimens of the Pikermian sample curated at the Museum National

Odontometric, morphological and biomechanical analyses

Odontometric

Odontometric data of the C. bruneti holotype and hypodigm were acquired using a Mitutoyo Digimatic caliper CD-8''CX on the original fossil material and on selected photographs obtained in Avizo Standard Edition and measured with ImageJ. Selected photographs of generated surfaces obtained in Avizo Standard Edition from µ-CT scans data of extant and extinct colobines (i.e., C. bruneti, C. williamsi and M. pentelicus) were used to calculate the NH/NR ratio [START_REF] Benefit | The permanent dentition and phylogenetic position of Victoriapithecus from Maboko Island, Kenya[END_REF] as well as additional dental metrics. Odontometric data of extant Colobinae were acquired directly on specimens as well as on high quality dental casts using a Mitutoyo Digimatic caliper CD-8''CX.

Further information regarding odontometric measurement protocols, sample size, ratio formulas and references are presented in footnotes of Fig. 1, SOM Figure S2, Table 3-4 and SOM Table S2.

Mandibular

Mandibular morphometric data from C. bruneti, C. williamsi and the extant Colobinae comparative sample were obtained from selected symphyseal and corporeal cross-sections obtained via GeoMagic Studio and Avizo Standard Edition on virtual specimens. Measurements of the symphyseal and corporeal cross-sections were obtained via ImageJ.

Further information regarding mandibular morphometric measurement protocol, sample size and ratio formulas can be found in footnotes of Fig. 6 and Table 5 as well as in SOM Fig. S1.

Postcranial

Data of the C. bruneti postcranial specimen were acquired via a Mitutoyo Digimatic caliper CD-8''CX on the original fossil material as well as from selected photographs obtained in Avizo Standard Edition and measured in ImageJ. All data from extant Cercopithecidae were acquired directly on specimens using a Mitutoyo Digimatic caliper CD-8''CX and from digital photographs using Image J. Further information regarding samples size and measurement protocol can be found in footnotes of Figure 9 and Table 6 as well as in SOM Figure S1.

Humeral geometric cross-sectional properties were obtained via Image J's plugin Bone J on virtual specimens. In order to acquire humeral mid-diaphyseal cross-sectional properties, the virtual image stacks were first aligned at their moments of inertia and then subjected to the calculation of geometric properties. The zone of interest (i.e., slice at mid-diaphysis) was subsequently obtained from the virtual image stack. Due to the lack of the humeral head of TM length +5%.

Body mass estimation

All equationsfor estimating body mass were taken from [START_REF] Delson | Body mass in Cercopithecidae (Primates, Mammalia) : Estimation and scaling in extinct and extant taxa[END_REF]. Further details and extended interpretations of body mass can be found in footnotes of Table 2 and SOM Table S1.

Results

Systematic paleontology

Order Primates Linnaeus, 1758; Rhinocolobus from the Turkana Basin. The mandibular corpus is shallow and thick, which contrasts greatly with that of Kuseracolobus, Rhinocolobus, Paracolobus and to some degree Colobus, but is not unlike that of Procolobus (Piliocolobus). The gonial region is unexpanded or expanded only a small amount. This contrasts with mandibles of Kuseracolobus, Rhinocolobus, Paracolobus mutiwa, and Colobus. Associated postcrania are known for C. williamsi from an associated skeleton from Koobi Fora (the morphology of which may not be typical for the South African material, see remarks below). It is distinguished from all other known colobines, except Dolichopithecus, in the degree of its adaptations for terrestrial habitus (Birchette, 1981;[START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]Ting, 2001)."

On a taxonomic level, the combination of a faint P 3 protocone, a precocious and marked dental wear, an orthognathic subnasal region with short premaxillae and maxillary sinuses (MS), a buttressed corpus bulging below M 1-2 as well as a symphysis with a straight, smooth and vertical labial face align the Chadian cercopithecid with the East and South African genus Cercopithecoides [START_REF] Freedman | The fossil Cercopithecoïdea of South Africa[END_REF][START_REF] Frost | Fossil Cercopithecidae from the Hadar Formation and surrounding areas of the Afar Depression, Ethiopia[END_REF][START_REF] Mckee | New species of Cercopithecoides from Haasgat, North West Province, South Africa[END_REF] (Table 12.

Cercopithecoides bruneti sp. nov. Holotype: TM 266 03-100, left and right hemimaxillae preserving dI 1 , dC 1 , dP 3-4 , C 1 , P 3-4 , M 1-2 . Paratype: TM 266 03-034, a fragmented left and right maxilla with I 2 , C 1 -P 4 ; TM 266 03-099, partial mandible preserving left P 3-M 3 and associated right P 3-M 1 ; TM 112 00-093, partial mandible preserving left P 3 ; TM 219 01-102, partial mandible preserving left C 1 and right I 1-M 2 ; TM 266 03-036, a right partial forelimb with sub-complete humerus, ulna and radius; TM 266 03-307, a sub-complete right femur. Upper dentition with moderate cusp relief and molar flare, M 2 paraloph width enlarged relative to tooth length, P 3 protocone highly reduced relative to paracone, dP 4 paraloph width enlarged relative to tooth length and marked breadth differential between P 3 and P 4 . Lower dentition with a narrow P 4 crown, a marked size differential between M 1 and M 2 , M 3 lacking a tuberculum sextum and possessing a buccolingually narrow hypoconulid relative to hypolophid breadth. Craniofacial morphology characterized by maxillary sinuses and an orthognathic sub-nasal region. Mandibular morphology characterized by a prominent inferior transverse torus (ITT), a corpus of moderate robustness with marked prominentia lateralis and a deep mandibular symphysis with a flat and vertical labial face that lacks a median mental canal.

Differential diagnosis Cercopithecoides bruneti specimens are larger than Microcolobus tugenensis (Ngorora Fm., Tugen Hills, Kenya), Microcolobus sp. (Nakali Fm., Baringo, Kenya) and the indeterminate small colobines from Kabasero (Ngorora Fm., Tugen Hills, Kenya), Teso Tadecho (Chorora Fm., Ethiopia), Beticha (Chorora Fm., Ethiopia), Lukeino (Lukeino Fm., Tugen Hills, Kenya), Lemudong'o (Lemudong'o Fm., Kenya) and colobine sp. A from LN-UN (Nawata Fm., Lothagam, Kenya). The Chadian colobine is smaller than the Miocene colobines from Menacer (Algeria) and Adu Asa (Adu Asa Fm., Ethiopia) as well as from the early Pliocene Kuseracolobus hafu. C. bruneti exhibits an enlarged paraloph relative to M 2 length with a crown shape ratio (CSR) matched by the small colobine from Lemudong'o (Fig. 1). C. bruneti further differs from M. tugenensis by the presence of an ITT, enlarged prominentia lateralis, a marked size differential between M 1 and M 2 , a less developed talonid on P 3 and a narrow P 4 crown. C. bruneti is distinct from the Kabasero colobines in having a more developed hypoconulid and a narrow hypolophid relative to M 3 length. Forelimb morphology of C. bruneti is unlike the Nakali colobine in having a reduced and straight ulnar olecranon process and a short and retroflexed humeral medial epicondyle. C. bruneti is distinguished from the Teso Tadecho colobine, Paracolobus enkorikae, the small Lemudong'o colobine and L. markgrafi by having a reduced P 3 protocone. A marked breadth differential between P 3 and P 4 further differentiates C. bruneti from P. enkorikae, the small colobine from Lemudong'o and L. markgrafi. C. bruneti is also distinguished from the Teso Tadecho colobine by a broader P 4 crown. C. bruneti further differs from P. enkorikae by a narrow P 4 crown, maxillary sinuses and a flat symphyseal labial face with no break in slope.

C. bruneti is morphologically distinct from L. markgrafi in having a narrow C 1 . C. bruneti differs from the Mpesida Beds colobine gen. and sp. A in lacking a buccally curved hypoconulid and accessory cuspules between entoconid and hypoconulid and in exhibiting a broader hypolophid relative to tooth length. C. bruneti differs from Kuseracolobus aramisi by a reduced P 3 protocone (a feature described as variable in K. aramisi), an early eruption of molars relative to the anterior dentition, a marked dp 4 CSR, a moderate flare on M 2 with a marked M 2 CSR (i.e., with a value > 100), a marked P 3-4 breadth differential, a corpus with a sharp inferior margin, the presence of a double mental foramen and an absence of tuberculum sextum. It further differs from C. williamsi in possessing a shorter planum alveolare, a relatively smaller hypoconulid, a superiorly placed genioglossal fossa, a less marked size differential between ITT and STT (Superior Transverse Torus), a less developed humeral deltoid crest, a less developed humeral medial trochlear keel and a broader zona conoidea. C. bruneti is distinct from C. meavae in having a marked breadth differential between P 3-4 , a broader dP 4 , a less marked size differential between M 1-2 , a shorter humeral medial epicondyle, a less developed humeral medial trochlear keel, a less rounded radial head and a gracile radial neck. C. bruneti also differs from C. alemayehui by a narrower P 3 crown and a broader M 2 paraloph relative to tooth length. C. bruneti displays an increased breadth differential between P 3-4 relative to C. kerioensis (Fig. 1) and is distinguished from C. haasgati by a narrower P 3 crown, an elongated P 4 crown and a less marked size differential between M 1 and M 2 .

Description of C. bruneti dentognathic morphology

TM 266 03-100 The type specimen TM 266 03-100 is a right and left hemimaxilla belonging to a juvenile individual and preserving much of the upper postcanine dentition (Table 3, Fig. 2). Of the upper anterior dentition, the dI 1 are highly worn, a small portion of the left dC 1 root is preserved and a large portion of the C 1 crown remained intact in the dental crypt. The dI 1 exhibits a lingual rootward extension of enamel onto the cervix and a mesiodistally compressed root unfused at its apex. The upper canine displays the features characteristic of male cercopithecids (i.e., deep mesial sulcus, a sharp distal margin, a convex buccal face and a mesiodistal elongation of the canine crown relative to breadth). Deciduous premolars are severely worn, consistent with a J5 dental wear stage while the postcanine dentition already show an A2 wear stage [START_REF] Ingicco | A deciduous and permanent dental wear stage system for assessing the age of Trachypithecus sp. specimens (Colobinae, Primates)[END_REF]. This early and heavy wear of the dentition is unusual among extant colobines, especially when considering the ontogenetic status of the specimen. The deciduous upper premolars exhibit a large amount of flaring and a CSR consistent with a bucco-lingual enlargement of those teeth. The dP 3 is bilophodont and devoid of crista obliqua; the dP 4 possesses a paraloph broader than the metaloph and a mesial shelf longer than the distal one (SOM Table 2). M 1-2 are in occlusion while dI 1 is still in place, confirming the presence of an early eruption of M 2 relative to the anterior dentition. The permanent premolars are preserved in their crypts and exhibit a characteristic colobine morphology. The P 3 crown is moderately broad and exhibits heteromorphic cusps with a faint protocone, a well-developed mesiobuccal flange, a paracone set distally relative to the protocone and a relatively narrow triangular mesial shelf compared to a squared-shape distal shelf. The P 4 crown is broad, displays a paracone higher than a distally set protocone, a high paracone relative to crown length, a high and sharp transverse loph, a marked mesiobuccal flange, a slight lingual cleft and a moderate length differential between mesial and distal shelves. In addition, there is a marked breadth differential between P 3-4 (Fig. 1). The M 2 s exhibit qualitatively thin enamel (Fig. 2) as well as a moderate amount of flare and crown relief relative to extant colobines. Note that the buccal parts of both M1 are missing as well as the hypocone of both M2 (Fig. 2). M 1-2 present deep and marked median lingual clefts, a poor development of the mesiodistal developmental groove, widely spaced lophs and moderately developed shelves (SOM Table S2) that support the taxonomic status of TM 266 03-100 as a colobine [START_REF] Benefit | The permanent dentition and phylogenetic position of Victoriapithecus from Maboko Island, Kenya[END_REF]. A marked buccal cingular ridge is present on M 2 and a poorly developed interconulus is observed at the base of the M 1 lingual cleft. A body mass of ~16.5kg is inferred from M 1-2 mesio-distal dimensions (SOM Table S1). Considering craniofacial morphology, TM 266 03-100 exhibits an orthognathic subnasal region with an anteriorly placed zygomatic process which originates low on the maxilla and above M 1 . This morphological pattern is seen in extant juvenile Colobinae and Cercopithecini of similar dental eruption stage (Fig. 3). The nasal aperture is straight in lateral view and tapers inferiorly to form an acute inferior margin in anterior view. The premaxilla is reduced and gives a square aspect to the premaxillo-maxillary complex. No maxillary or infraorbital fossae are observed. A large infraorbital foramen is present on the inferior portion of the orbital margin of the right hemimaxilla. The hard palate extends posteriorly at the level of M 2 . Maxillary sinuses (MS) invade the lower portion of the maxilla, extend anteriorly at the level of M 1 and are pierced by the roots of M 1-2 . TM 266 03-034 is a fragmented anterior maxilla preserving most of the adult anterior dentition (Fig. 2). I 2 displays a parallelogram-shaped and mesially angled crown with a poorly developed basal cingulum, a faint lateral prong, a thin layer of enamel on the occlusal surface, a well-defined and horizontal cervix, a markedly convex labial face and no sulcus. C 1 presents a narrow crown with a long axis obliquely oriented relative to P 3-4 , a low crown cusp with a raised cingulum on the mesial margin, a raised distal margin on the talonid and a mesial groove continuing from the crown onto the roots. TM 266 03-034 exhibits a female morphology with a low crowned C 1 relative to tooth length. Although fragmented, the P 3 bucco-lingual dimension is in the size range of TM 266 03-100 (SOM Table S2) and is morphologically consistent with the C. bruneti holotype in exhibiting a flange-like buccal margin and a raised paracone associated with a faint and mesially offset protocone. A slight portion of the lateral margin of the right nasal aperture is preserved and set vertically relative to the occlusal plane. TM 266 03-099, TM 112 00-093 and TM 219 01-102 consist of adult mandibular remains allocated to the C. bruneti hypodigm (Fig. 45).

TM 266 03-099 displays a wear pattern consistent with an A6 dental wear stage [START_REF] Ingicco | A deciduous and permanent dental wear stage system for assessing the age of Trachypithecus sp. specimens (Colobinae, Primates)[END_REF]. The P 3 crown is narrow and presents a large protoconid but no paraconid nor metaconid, the mesiobuccal flange is developed, upright, and does not extend below the alveolar margin.

The degree of development of the P 3 flange is consistent with a male morphology. The P 4 is bicuspid, lacks an entoconid and displays a protoconid broader than the distally offset metaconid and an elongated crown with a moderate mesiobuccal flange. Mesial and distal lophids are of nearly equal width on M 1-2 but there is a marked size differential between M 1 and M 2 (SOM Fig. S2). The trigonid basin is reduced on all molars, and the M 3 lacks a tuberculum sextum but bears a buccally placed hypoconulid which is small relative to hypolophid breadth.

The labial symphyseal face is flat and vertical with a minute symphyseosum foramen placed at its mid-height. It lacks rugosities, sub-incisal hollowing and a median mental canal (Fig. 45). The inferior margin of the symphysis is sharp with a rugose infero-lingual portion, a developed digastric spine and a poorly imprinted digastric fossa. The planum alveolare is straight and extends to the mesial part of P 3 . The symphysis is robust (Fig. 45) and presents a bulbous and extensive ITT that reaches the mesial part of P 4 . The infero-lingual margin of the corpus is sharp and inferiorly lacks an imprinted digastric fossa at M 1 level and superiorly an inter-toral sulcus.

Prominentia laterales are prominent and extend anteriorly to the mesial portion of P 4 . The corpus is deep and bulges below M 1 , the linea obliqua merges with the corpus at the level of M 1- 2 contact and the extramolar sulcus is narrow.

TM 112 00-093 morphology is consistent with that of TM 266 03-099 in exhibiting a similar symphyseal topography but with a less developed ITT extending only to the level of P 3 and a less acute symphyseal inferior margin. The planum alveolare is slightly concave and the STT overhangs a shallow genioglossal fossa. The corpus morphology is also consistent with TM 266 03-099 but exhibits a marked imprinting of the digastric fossa and submandibular fossa, respectively below P 4 -M 1 and M 2-3 . Of the entire dental row, only the P 3 crown is preserved. The mesiobuccal flange is short and in accordance with a female morphology. The incisor row is narrow. The base of the M 3 crown tapers distally.

TM 219 01-102 is a fragmented mandible preserving the symphysis and hints of the superior portion of the right and left corpus. TM 219 01-102 exhibits peg-like incisors with poorly developed cingulum and a narrow incisal row. Canines are robust, labially recurved, and present an extensive talonid devoid of any tubercles. The canine root bears a faint mesial groove. The inferior margin of the symphysis is eroded but the toral morphology is clearly colobine-like with an extensive and bulbous ITT reaching the mesial part of M 1 . The symphysis is vertical, and a slight hint of the linea obliqua is preserved on the upper part of the corpus at the level of M 2 .

Canine dimensions and morphology are consistent with identification as a male. In addition, dental and mandibular dimensions of TM 219 01-102 are congruent with those of TM 266 03-034 (Tables 45).

Body masses inferred from dental dimensions ranged from ~ 8.45kg for TM 112 00-093 to ~ 13.3kg and ~14.4kg (using equations from [START_REF] Delson | Body mass in Cercopithecidae (Primates, Mammalia) : Estimation and scaling in extinct and extant taxa[END_REF], respectively for TM 219 01-102 and TM 266 03-099 (SOM Table S1).

Comparative aspect of C. bruneti dentognathic anatomy

The C. bruneti dP 4 possess a paraloph broader than the metaloph (SOM Table S2), a characteristic variable among Cercopithecoidea but mostly observed on Victoriapithecidae and Cercopithecinae [START_REF] Benefit | Phylogenetic, paleodemographic, and taphonomic implications of Victoriapithecus deciduous teeth from Maboko, Kenva[END_REF]. Nevertheless, the absence of a crista obliqua, the bilophodont state of dP 3-4 and the marked dP 4 mesial shelf length relative to the distal one clearly aligns C. bruneti with crown cercopithecids [START_REF] Benefit | Phylogenetic, paleodemographic, and taphonomic implications of Victoriapithecus deciduous teeth from Maboko, Kenva[END_REF]. The dP 4 CSR is consistent with an enlargement of the tooth, similar to victoriapithecids but also to the putative colobine dP 4 from Menacer (SOM Fig. S2). Furthermore, the early eruption of M 2 relative to the anterior dentition observed in C. bruneti is typical of Colobinae [START_REF] Harvati | Dental eruption sequences in fossil colobines and the evolution of primate life histories[END_REF]. Although an early molar eruption relative to anterior dentition was previously documented in M. pentelicus, the extreme condition of the early eruption of M 2 relative to I 1 observed in C. bruneti was previously unknown among fossil colobines whereas it is documented either as a variant (e.g Colobus angolensis) or as a constant (e.g Presbytis spp.) among extant Colobinae [START_REF] Harvati | Dental eruption sequences in fossil colobines and the evolution of primate life histories[END_REF]. C. bruneti upper molar morphology is similar to those of early Eurasian as well as North and East African colobines in exhibiting a basal flaring associated with a lack of sharp shearing crests [START_REF] Benefit | Miocene fossil Cercopithecoids from Kenya[END_REF][START_REF] Rossie | Early cercopithecid monkeys from the Tugen Hills, Kenya[END_REF][START_REF] Suwa | Newly discovered cercopithecid, equid and other mammalian fossils from the Chorora Formation, Ethiopia[END_REF]. Even slightly worn, a quantification of C. bruneti left M 2 occlusal relief (i.e., NH/NR ratio, Fig. 1) yields a value higher than those observed among the penecontemporaneous Eurasian colobine M. pentelicus and the North African colobines from Menacer and As Sahabi [START_REF] Delson | Fossil colobine monkeys of the circum-Mediterranean region and the evolutionary history of the Cercopithecidae (Primates, Mammalia)[END_REF][START_REF] Benefit | New Fossil Cercopithecoids from the Late Miocene of As Sahabi, Libya[END_REF]. C. bruneti subnasal morphology is consistent with the poor maxillary projection observed in Cercopithecoides spp. and Kuseracolobus spp. The deep and slender corpus as well as the deep symphysis of C. bruneti is similar to the early Pliocene C. kerioensis [START_REF] Leakey | Cercopithecidae from Lothagam[END_REF]. The Chadian Cercopithecoides further shares with C. kerioensis and C. meavae a moderate breadth of the M 3 hypolophid relative to tooth length and an absence of a median mental canal. C. bruneti is similar to the South African C. williamsi sample in exhibiting a marked P 3-4 breadth differential (Fig. 1,3) and a marked M 1-2 size differential (SOM Fig. S2). The enlargement and the square aspect of the C. bruneti upper second molar are also consistent with the South African Cercopithecoides sample (i.e., C. williamsi and C. haasgati) (Fig. 1,3). Relative to extant colobines, C. bruneti dentognathic morphology is consistent with a Colobini morphology.

Indeed, a narrow P 3 crown with heteromorphic cusps [START_REF] Swindler | Metric and morphological variability in the dentition of colobine monkeys[END_REF], a height differential between lingual and buccal P 4 cusp [START_REF] Gilbert | Miocene Cercopithecoidea from the Tugen Hills, Kenya[END_REF], a distally offset P 4 metaconid [START_REF] Swindler | Metric and morphological variability in the dentition of colobine monkeys[END_REF], a broad P 4 protoconid relative to metaconid [START_REF] Swindler | Metric and morphological variability in the dentition of colobine monkeys[END_REF], a narrow P 4 crown, an elongated C 1 [START_REF] Pan | Dental morphometric variation between African and Asian colobines, with special reference to the other Old World monkeys[END_REF]) and a poorly developed (i.e., Colobus-like) digastric fossa [START_REF] Groves | The taxonomic diversity of the Colobinae of Africa[END_REF] aligns C. bruneti with the extant Colobini (Fig. 3). In spite of morphological affinities with the African colobine tribe, C. bruneti lacks the long and steeply inclined planum alveolare, the inferiorly placed genioglossal fossa and the diminutive ITT seen among several taxa of Colobus (Fig. 56). C. bruneti symphyseal topography is most consistent with the morphology exhibited by Piliocolobus but it does not exhibit the marked dental occlusal relief seen in the extant genus (Fig. 56).

Description of C. bruneti postcranial morphology

A sub-complete right forelimb (i.e., TM 266 03-036) composed of humerus, radius and ulna as well as a partial femur (i.e., TM 266 03-307) are here included in the C. bruneti hypodigm (Fig. 7). Collected from the same locality, it is parsimonious to assume that the fore-and hindlimbs come from the same taxon (i.e., C. bruneti). Joint congruency supports the hypothesis of the forelimb elements belonging to the same specimen.

TM 266 03-036 The postero-distal portion of the humeral head is preserved and is flanked by well-defined distal margin of the greater and lesser tuberosities. In posterior view, the medial part of the surgical neck is markedly concave and accommodates the insertion of the coracobrachialis profundus muscle. The humeral proximal diaphysis is fractured in its proximal and distal portion. It is surrounded by sharp crista tuberculi majoris and crista tuberculi minoris.

Those crests are poorly developed and accommodate proximally set attachment sites for teres major and pectoralis major muscles. The posterior aspect of the proximal diaphysis is salient and bears moderate sites of attachment for the lateral head of the triceps brachii muscle. The deltoid tuberosity is flat, poorly developed, and does not extend below mid-diaphysis. The humeral diaphysis is gracile and elliptical in cross-section at mid-diaphysis, with a long-axis running anterolateral-to-posteromedially. The humeral shaft is straight in the anteroposterior plane but curved medially in the mediolateral plane. The posterior aspect of the distal portion of the diaphysis is flattened and exhibits a poorly developed lateral supracondylar ridge. The distal epiphysis is fractured and separated from the humeral shaft. Most of the humeral trochlea and zona conoidea are preserved (Fig. 7). The antero-proximal part and a slight hint of the proximolateral portion of the capitulum are preserved. The anterior aspect of the distal epiphysis is characterized by a wide and deep radial fossa, a shallow and poorly delineated coronoid fossa, a moderate-sized trochlea, a moderately developed medial trochlear keel compared to cercopithecins that is set obliquely relative to the long-axis of the shaft, a well-defined anterior margin of the medial trochlear keel, a faint lateral trochlear keel and a large zona conoidea (Fig. 7). The posterior aspect of the distal epiphysis exhibits a deep and oval-shaped olecranon fossa that presents a septal aperture, a moderate breadth differential between its lateral and medial pillar, a short and retroflexed medial epicondyle and a salient posterior margin of the lateral pillar of the olecranon fossa.

The cresting of the proximal portion of the ulnar olecranon process is damaged (Fig. 7). The olecranon process is short and aligned with the long axis of the diaphysis. The posterior margin of the proximal epiphysis is slightly convex. The anconeal process is short and does not project markedly anteriorly. Although eroded, the proximal margin of the anconeal process is asymmetric, with a proximal projection of its lateral margin. The ulnar sigmoid notch is fractured at its mid-height. The ulnar trochlear surface is poorly waisted and congruent with the moderate enlargement of the humeral trochlea. The postero-medial portion and the most anterior portion of the coronoid process is missing as is the postero-lateral portion of the radial notch. The anterior margin of the coronoid process is wide and is antero-distally slanted, consistent with a shallow humeral coronoid fossa. The radial notch is expanded, presents a waisting between its anterior and posterior facet and bears a lateral margin oriented posteriorly. The medial face of the proximal epiphysis is fractured longitudinally but exhibits a deep and wide insertion surface for the flexor digitorum profundus muscle that extends distally through the proximal part of the diaphysis. The ulnar diaphysis is fractured in its mid-and distal portion, resulting in separate fitting parts. The proximal portion of the diaphysis exhibits a raised supinator crest that borders a large insertion surface for the supinator muscle. The diaphysis is gracile and straight in lateral view. A raised pronator ridge is present on the distal portion of the diaphysis. The distal epiphysis is broken away.

The radius preserves the damaged proximal half. Only the antero-lateral portion of the radial head is missing (Fig. 7). The radial head is elliptical with the long-axis running antero-posteriorly.

The articular fovea of the radial head is placed posteriorly and is bordered anteriorly by a wide peripheral articular surface and posteriorly by a proximally-raised margin. The radial head is strongly tilted in medio-lateral view. The neck is short, gracile, and bears a marked bicipital tuberosity divided in two components by a deep sulcus. The medial margin of the proximal portion of the diaphysis is slightly concave and exhibits a faint interosseous crest whereas the lateral margin bears signs of rugosities for the supinator muscle.

TM 266 03-307 is a right femur with a damaged proximal epiphysis preserving the femoral neck, the postero-proximal aspect of the greater trochanter, a slight hint of the proximal portion of the intertrochanteric crest and the medial portion of the lesser trochanter. The distal third is broken away (Fig. 7). The neck is antero-posteriorly compressed, bears no grooving for the obturator externus tendon, forms an obtuse neck-shaft angle with the femoral shaft and is poorly anteverted. The cortical bone distribution of the femoral neck is asymmetric with a cortical bone distribution skewed toward the inferior margin of the neck, as in most extant cercopithecids [START_REF] Rafferty | Structural design of the femoral neck in primates[END_REF]. The trochanteric fossa is rounded, shallow and does not extend distally below the insertion for quadratus femoris. The shaft is robust and slightly bowed anteriorly. The medial margin of the lesser trochanter is salient and projects postero-medially.

Inferiorly to the lesser trochanter is a rugose zone for the pectineal line and gluteal tuberosity.

Although fragmented, TM 266 03-307 is here included in the C. bruneti hypodigm based both on its estimated body mass (SOM Table S1), which is consistent with values obtained from dental dimensions, and on its provenance from the C. bruneti type locality (i.e., locality n°266).

Comparative anatomy and functional morphology of C. bruneti postcranial anatomy

C. bruneti upper limb morphology presents clear colobine affinities in exhibiting a prominent zona conoidea [START_REF] Frost | Fossil Cercopithecidae from the Hadar Formation and surrounding areas of the Afar Depression, Ethiopia[END_REF], a marked breadth differential between the lateral and medial pillar of the olecranon fossa, an extensive ulnar insertion site for flexor digitorum profundus [START_REF] Krentz | Postcranial anatomy of extant and extinct species of Theropithecus[END_REF][START_REF] Desilva | Cercopithecoid primate postcranial fossils from Cooper's D, South Africa[END_REF], a marked asymmetry of the peripheral articular surface of the radial head [START_REF] Nakatsukasa | Earliest colobine skeletons from Nakali, Kenya[END_REF] and a poorly defined interosseous crest on the radius [START_REF] Desilva | Cercopithecoid primate postcranial fossils from Cooper's D, South Africa[END_REF]. Considering humeral morphology, C. bruneti is similar to C. williamsi, C. kimeui and C. meavae in exhibiting a retroflexed medial epicondyle and a deep distal articular surface antero-posteriorly (i.e., HDB variable in Table 6) [START_REF] Frost | Fossil Cercopithecidae from the Hadar Formation and surrounding areas of the Afar Depression, Ethiopia[END_REF][START_REF] Jablonski | Systematic paleontology of the large colobines[END_REF]). An abbreviated and retroflexed medial epicondyle has been linked to terrestrial locomotor behavior and particularly to stability enhancement of the humero-ulnar joint in pronated position [START_REF] Jolly | The evolution of the baboons[END_REF][START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]. A moderate extension of the deltoid tuberosity and a proximal insertion of the teres major and pectoralis major illustrate an enhancement of rapid flexion/adduction of the C. bruneti elbow. The Chadian colobine exhibits an elliptical cross-section of the humeral mid-diaphysis, consistent with a structural adaptation related to stress dissipation of mechanical loadings engendered during terrestrial locomotor behavior (Fig. 9) [START_REF] Carlson | Comparisons of limb structural properties in free-ranging chimpanzees from Kibale, Gombe, Mahale, and Taï Communities[END_REF][START_REF] Patel | Humeral cross-sectional shape in suspensory primates and sloths: Long bone cross-sectional shape[END_REF]. Although structurally adapted to withstand mechanical stress and rapid flexion/extension in a terrestrial context, the functionally mosaic humeral morphology of C. bruneti exhibits characters reminiscent of arboreal locomotor habits. The enlargement of the humeral trochlea of C. bruneti is moderate, translating a weightbearing function to the humero-ulnar joint as in extant arboreal Colobinae [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF].

Although marked relative to extant Colobinae (Fig. 8), the development of the medial trochlear keel of C. bruneti is moderate relative to C. williamsi and C. meavae and reflects a humero-ulnar joint poorly adapted to restrict medial movement as occurred during leaping and/or terrestrial activities (Fig. 9) [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF][START_REF] Harrison | New postcranial remains of Victoriapithecus from the middle Miocene of Kenya[END_REF][START_REF] Frost | Fossil Cercopithecidae from the Hadar Formation and surrounding areas of the Afar Depression, Ethiopia[END_REF]. The humeral shaft of C. bruneti is gracile and accords well with generating low reaction forces and an adaptation to compliant substrate, as found in an arboreal context [START_REF] Nakatsukasa | Morphology of the humerus and femur in African mangabeys and guenons: functional adaptation and implications for the evolution of positional behavior[END_REF]. The insertion for the coracobrachialis profundus muscle is depressed and the insertion for the flexor digitorum profundus muscle on the ulna is marked and extensive, as in arboreal cercopithecids [START_REF] Krentz | Postcranial anatomy of extant and extinct species of Theropithecus[END_REF]. Relative to ulnar morphology, the olecranon process of C. bruneti is short and, coupled with a deep humeral olecranon fossa, reflects an important degree of elbow extension. The olecranon process is straight and not consistent with the anteflexed olecranon of arboreal colobines (Fig. 8) nor with the retroflexed olecranon of highly terrestrial Cercopithecinae [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]. In addition, the straight ulnar shaft contrasts with the posteriorly convex shaft of arboreal colobines (Fig. e 8) [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]. Consistent with the previously inferred weightbearing function of the humero-ulnar joint, C. bruneti exhibits an enlarged humeral articular facet of the ulnar sigmoid notch (Table 6). A short anconeal process and a distally slanted coronoid process confirm the presence of a poorly stabilized humero-ulnar joint in C. bruneti. This flexibility of the elbow joint is consistent with an arboreal component in the locomotor behavior of the Chadian colobine. In accordance with the humeral morphology, the ulnar shaft is gracile. A marked elliptical radial head is observed in both extant Colobus and C. bruneti [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]. With a marked proximal projection of its posterior margin and a strong medial tilt, the radial head of C. bruneti is consistent with a reinforcement of the humero-radial joint in pronated position [START_REF] Rose | Another look at the anthropoid elbow[END_REF]. The radial neck of C. bruneti is gracile and confirms the patterns of a poorly buttressed brachium and antebrachium. Considering femoral morphology, the neckshaft angle of C. bruneti is obtuse, contrasting with the acute angle seen among hyperterrestrial cercopithecids and reflecting an increase in hindlimb range of motion [START_REF] Bacon | La locomotion des primates du Miocène d'Afrique et d'Europe : Analyse fonctionnelle des os longs du membre pelvien et systematique[END_REF][START_REF] Frost | Fossil Cercopithecidae of the Afar Depression, Ethiopia: species systematics and comparison to the Turkana Basin[END_REF].

Discussion

Cercopithecoides bruneti sp. nov. from the Late Miocene of Central Africa, Chad adds to the antiquity and to the extensive geographical range of the genus Cercopithecoides. The mandibular morphology of C. bruneti corroborates the presence of a relatively deep and slender corpus among early representatives of this genus (Fig. 4) [START_REF] Leakey | Cercopithecidae from Lothagam[END_REF][START_REF] Jablonski | Cercopithecoidea[END_REF]. It also documents a departure from the cercopithecine-like symphyseal topography documented in Miocene East African stem Colobinae [START_REF] Benefit | Miocene fossil Cercopithecoids from Kenya[END_REF] and brings evidence of a diversity in mandibular morphology among Cercopithecoides.

Discrepancies in corporeal and symphyseal cross-sectional geometry and morphology further inform us on divergent structural adaptations to withstand at least different stress and loading regimes during feeding behavior [START_REF] Ross | Innovative approaches to the relationship between diet and mandibular morphology in primates[END_REF]. The relationships between diet, feeding behavior and mandibular morphology are not straightforward among primates [START_REF] Daegling | Feeding, diet, and jaw form in west african Colobus and Procolobus[END_REF][START_REF] Daegling | Feeding behavior and diet in Paranthropus boisei: The limits of functional inference from the mandible[END_REF], blurring the ecomorphological signal inferred from corporeal and symphyseal morphology among early and late representatives of Cercopithecoides taxa. A frugivorous component was identified in the C. williamsi diet through Dental Microwear Textural Analysis (DMTA) (Williams and Geissler, 2014), and several proxies point to a fruit-dominated diet among Eurasian and several Late Miocene early colobines [START_REF] Merceron | Folivory or fruit/seed predation for Mesopithecus, an earliest colobine from the late Miocene of Eurasia?[END_REF][START_REF] Rossie | Early cercopithecid monkeys from the Tugen Hills, Kenya[END_REF]Thiery et al., 2017). In contrast, the East African Miocene colobines from Lukeino Fm. and Mpesida Beds, respectively at ca. 5.7 and 6.37 Ma, bear qualitative and quantitative (i.e., NH/NR) dental morphological hallmarks of adaptation to a leaf-dominated diet [START_REF] Gilbert | Miocene Cercopithecoidea from the Tugen Hills, Kenya[END_REF]. C. bruneti occlusal relief is moderate relative to extant colobines but stands apart from the cercopithecine-like occlusal relief documented in North African [START_REF] Benefit | New Fossil Cercopithecoids from the Late Miocene of As Sahabi, Libya[END_REF] and Eurasian Miocene colobines (Fig. 1). Accordingly, C.

bruneti dental morphology provides evidence of an increase in occlusal relief and thus supports an increase in leaf consumption at ca. 7 Ma among African colobines relative to penecontemporaneous early African and Eurasian colobines. Subsequent adaptation to the consumption of abrasive food items had been postulated in regard to the severe degree of dental attrition wear stages observed among several Cercopithecoides taxa [START_REF] Szalay | Evolutionary history of the primates[END_REF][START_REF] Jablonski | Cercopithecoidea[END_REF]. C. bruneti provides the earliest evidence of this peculiar dental wear pattern which may be linked to grit transport due to the onset of the Sahara Desert in Central Africa at ca. 7 Ma [START_REF] Schuster | The Age of the Sahara Desert[END_REF].

The associated colobine postcranial remains from Nakali shed light on arboreal locomotor behavior among Late Miocene African stem Colobinae (Fig. 8) [START_REF] Nakatsukasa | Earliest colobine skeletons from Nakali, Kenya[END_REF].

Further evidence of arboreality was inferred among several groups of early colobine postcranial remains from other Miocene East African localities [START_REF] Hlusko | A new Late Miocene species of Paracolobus and other Cercopithecoidea (Mammalia: Primates) fossils from Lemudong'o, Kenya. Kirtlandia[END_REF][START_REF] Gilbert | Miocene Cercopithecoidea from the Tugen Hills, Kenya[END_REF].

Contrasting with a plesiomorphic arboreal postcranial bauplan, the radiation of the Plio-Pleistocene Cercopithecoides taxa has been associated with locomotor behavior that includes moderate to marked terrestrial locomotor habits [START_REF] Jablonski | Systematic paleontology of the large colobines[END_REF]. Morphofunctional adaptation to terrestrial locomotor behavior is inferred among Eurasian Miocene colobines (Fig. 8) (Youlatos et al., 2012;Youlatos and Koufos, 2010) but tenuous evidence of terrestriality was postulated from fragmentary and isolated Miocene colobine forelimb remains from East Africa [START_REF] Leakey | Cercopithecidae from Lothagam[END_REF]. A nearly complete forelimb attributed here to C. bruneti firmly demonstrates a partial reacquisition of terrestrial locomotor behavior among colobines as early as the Late Miocene (Fig. 89) and confirms the autapomorphic condition of terrestrial habits in the locomotor behavior of the genus Cercopithecoides. Additionally, the Chadian colobine documents a morpho-functional trade-off typical of Cercopithecoides, with an elbow joint adapted to withstand stress engendered by terrestrial locomotor habits and to promote joint flexibility during foraging and frequent arboreal locomotor habits [START_REF] Jablonski | Systematic paleontology of the large colobines[END_REF]. In addition to shedding light on the locomotor diversity of early African colobines, C. bruneti also establilshes the presence of an extreme variant of early molar eruption pattern among Late Miocene African colobines and confirms the diversity of dental eruption pattern inferred among early colobines [START_REF] Harvati | Dental eruption sequences in fossil colobines and the evolution of primate life histories[END_REF].

Toros-Menalla is similar to other East African Miocene cercopithecid-bearing localities in exhibiting an abundance of Colobinae relative to Cercopithecinae [START_REF] Harrison | Cercopithecids (Cercopithecidae, Primates)[END_REF]. It also brings evidence for a substantial ecomorphological diversity among Miocene colobines, giving support to the hypothesis of a short-fused model of the adaptive radiation of Colobinae [START_REF] Frost | Cercopithecidae[END_REF]. The affinity of the East African C. williamsi with the tribe Colobini was recently reinforced by the demonstration of its marked pollical reduction [START_REF] Frost | The Hand of Cercopithecoides williamsi (Mammalia, Primates): Earliestevidence for thumb reduction among Colobine monkeys[END_REF]. However, the affinity of the genus Cercopithecoides with crown or stem Colobini remains unclear. Fragmentary remains from an indeterminate colobine from the Lukeino Fm. demonstrates the presence of a synapomorphic Colobini astragalar morphology at ca. 6.1 Ma [START_REF] Gilbert | Miocene Cercopithecoidea from the Tugen Hills, Kenya[END_REF]. Unlike the colobine gen. and sp. B from Lukeino Fm., no clear synapomorphic postcranial characters permit to assign C. bruneti within the Colobini crown group. However, the molecularly estimated divergence times of extant Colobini taxa (i.e., 8-6 Ma) is clearly in the time range spanned by C. bruneti (Ting, 2008). On one hand, the Chadian colobine exhibits clear dental and mandibular morphological affinities with the African tribe (Fig. 3,5). On the other hand, it retains plesiomorphic features observed among morphologically conservative Miocene colobines (i.e., square molars, moderate occlusal relief and MS) (Fig. 3). Additionally, the temporal setting of C. bruneti and its phenetic affinities with the early Pliocene C. kerioensis are in favor of its basal position in the Cercopithecoides lineage. Altogether, C. bruneti supports a placement of the genus Cercopithecoides among the stem (rather than crown) Colobini group.

Summary and conclusions

The newly described postcranial and dentognathic fossil cercopithecid material from the Late Miocene hominin-bearing fossiliferous area of Toros-Menalla sheds light on a previously unknown spatial setting during a poorly sampled, yet critical, period of the adaptive radiation of colobine monkeys in Africa.

We demonstrate the oldest occurrence of a speciose early colobine genus previously and securely known only from Plio-Pleistocene deposits of eastern and southern Africa. In addition to further documenting the morphological diversity of Cercopithecoides, C. bruneti supports the presence of gracile mandibular morphology as well as the autapomorphic condition of terrestrial locomotor habits among early representatives of its genus. While phenetic affinities of Cercopithecoides with the Colobini crown group are corroborated, in-depth analysis of the dentognathic morphology of C. bruneti underlined its basal position by revealing its morphological departure from the mandibular and dental anatomy of extant African colobines, lending further support to a phylogenetic placement of Cercopithecoides into the stem Colobini group.

As an anatomical hallmark of extant colobines, the emergence of a folivorous dental morphology is of prime interest in the understanding of the colobine adaptive radiation. On this aspect, C. bruneti departs from the cercopithecine-like occlusal relief and the subsequently inferred frugivory documented among penecontemporaneous colobines, bringing evidence of an increase in leaf consumption among African Miocene colobines. Similarly, we demonstrate the presence of a terrestrial signal in the C. bruneti postcranial morphology, confirming the alteration of the colobine postcranial arboreal bauplan as early as 7 Ma in Africa.

By providing evidence of substantial ecomorphological diversity among Miocene colobines, we highlight the role of Central Africa not only in the radiation of extant cercopithecids but also in the early evolutionary history of those widespread primates. Thiery, G., Gillet, G., Lazzari, V., Merceron, G., Guy, F., 2017. Was [START_REF] Freedman | The fossil Cercopithecoïdea of South Africa[END_REF][START_REF] Delson | Fossil colobine monkeys of the circum-Mediterranean region and the evolutionary history of the Cercopithecidae (Primates, Mammalia)[END_REF][START_REF] Frost | Fossil Cercopithecidae of the Afar Depression, Ethiopia: species systematics and comparison to the Turkana Basin[END_REF][START_REF] Frost | Partial cranium of Cercopithecoides kimeui Leakey, 1982 from Rawi Gully, southwestern Kenya[END_REF][START_REF] Frost | Early Pliocene Cercopithecidae from Woranso-Mille (Central Afar, Ethiopia) and the origins of the Theropithecus oswaldi lineage[END_REF][START_REF] Leakey | Cercopithecidae from Lothagam[END_REF]Leakey, 1987;[START_REF] Hlusko | A new large Pliocene colobine species (Mammalia: Primates) from Asa Issie, Ethiopia[END_REF][START_REF] Hlusko | A new Late Miocene species of Paracolobus and other Cercopithecoidea (Mammalia: Primates) fossils from Lemudong'o, Kenya. Kirtlandia[END_REF][START_REF] Benefit | New Fossil Cercopithecoids from the Late Miocene of As Sahabi, Libya[END_REF][START_REF] Gilbert | Cercopithecidae[END_REF][START_REF] Jablonski | Systematic paleontology of the large colobines[END_REF][START_REF] Suwa | Newly discovered cercopithecid, equid and other mammalian fossils from the Chorora Formation, Ethiopia[END_REF]. pentelicus (n=6;PIK 244, 245, 355, 356, 1429PIK 244, 245, 355, 356, , 1727)) pentelicus (n=7;PIK 244, 245, 355, 356,1727PIK 244, 245, 355, 356, ,1728PIK 244, 245, 355, 356, ,1729)), extant Papio ssp. (n=17), extant Colobini (n=34) and extant Presbytini (n=22). Medial trochlear keel development calculated and measured as in [START_REF] Frost | Fossil Cercopithecidae from the Hadar Formation and surrounding areas of the Afar Depression, Ethiopia[END_REF]. (C.) Boxplot of the Imax/Imin ratio of C. bruneti (n=1; TM 266 03-034), extant cercopithecines (n=6) and extant colobines (n=17). The presence of MS is not clearly asserted [START_REF] Gilbert | Cercopithecidae[END_REF]. Dental metrics in mm and dental metrics of right teeth given in brackets. MD: mesio-distal dimension; BL: bucco-lingual dimension; MBL: bucco-lingual dimension at the paraloph. Measurement protocol from [START_REF] Benefit | The permanent dentition and phylogenetic position of Victoriapithecus from Maboko Island, Kenya[END_REF]. Extended dental metrics in Table S2.

BM (kg)

1 Measurements acquired using a Mitutoyo Digital Calliper CD-8''CX on original specimens 2 Measurements acquired on ImageJ through selected photographs of the segmented model obtained in Avizo Standard Edition Dental metrics in mm and right teeth metrics given in brackets. Dental indices and measurement protocols from [START_REF] Benefit | The permanent dentition and phylogenetic position of Victoriapithecus from Maboko Island, Kenya[END_REF]Harrison and Harris, 1996). All measurements acquired using a Mitutoyo Digital Calliper CD-8''CX on original specimens. MD: mesio-distal dimension; BL: bucco-lingual dimension; OL: Occlusal length; TL: Total length; FL: Flange length as in [START_REF] Benefit | The permanent dentition and phylogenetic position of Victoriapithecus from Maboko Island, Kenya[END_REF]; MBL: bucco-lingual dimension at the metalophid; HBL: bucco-lingual dimension at the hypolophid; HYPOB: buccolingual dimension at the hypoconulid. All measurements in mm and acquired using a Mitutoyo Digital Calliper CD-8''CX. HTL: Humeral total length; HML: Humeral medio-lateral diameter at mid-diaphysis (HTL+5%); HAP: Humeral antero-posterior diameter at mid-diaphysis (HTL+5%); HAW: Humeral articular width measured as in [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]; MEPP: Medial epicondyle posterior projection measured as in [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]; TW: Humeral trochlear width measured as in [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]; HAH: Humeral distal articular height measured as in [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]; MKPD: Humeral medial keel distal projection measured as in [START_REF] Frost | Fossil Cercopithecidae from the Hadar Formation and surrounding areas of the Afar Depression, Ethiopia[END_REF]; HCW: Humeral capitulum and zona conoidea width measured as in [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]; HDW: Humeral distal epiphysis width measured as in [START_REF] Harrison | New postcranial remains of Victoriapithecus from the middle Miocene of Kenya[END_REF]; HDB: Humeral distal epiphysis breadth measured as in [START_REF] Rose | Another look at the anthropoid elbow[END_REF]; MEA: Medial epicondyle angulation as in the protocol presented in ;OPH: Ulnar olecranon process height measured as in (Ciochon, 1986); TNH=Ulnar trochlear notch height measured as in [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]; CPH: Ulnar coronoid process height measured as in [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]; TWMH: Ulnar trochlear width at mid-height measured as in [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]; RHAP: Radial head antero-posterior diameter measured as the long axis of the radial head; RHML: Radial head medio-lateral diameter measured as the short axis of the radial head; RNAP: Radial neck antero-posterior diameter measured as the long axis of the radial neck; RNML: Radial neck medio-lateral diameter as the short axis of the radial neck; RTP: Radial tuberosity projection measured as in [START_REF] Birchette | The postcranial skeleton of Paracolobus chemeroni[END_REF]; *Due to conservation state, the measurement of TM 266 03-307 are given here as estimated value. FAP: Femoral mid-diaphysis antero-posterior diameter (taken as a rough estimate of the mid-diaphyseal point and diaphysis subject to distortion); FML: Femoral middiaphysis medio-lateral diameter (taken as a rough estimate of the mid-diaphyseal point and diaphysis subject to distortion); FNAP: Femoral neck antero-posterior diameter; FNSI: Femoral neck medio-lateral diameter (femoral neck superior portion abraded); FNSA: Femur neck-shaft angle.

1 Measurements taken from selected photographs.

Measurements

  d'Histoire Naturelle (MNHN, France). Postcranial and odontometric data for extant Cercopithecidae were gathered directly from specimens provided by PALEVOPRIM (Université de Poitiers, France); the Museum National d'Histoire Naturelle (MNHN, France); the Royal Museum of Central Africa (RMCA, Belgium); the Natural History Museum of Basel (NMB, Switzerland); the Anthropological Institute and Museum, University of Zurich (AIM-UZH, Switzerland) and the Musée des Confluences, Lyon (MHNL, France). Additional odontometric data of extant Colobini were also gathered from high quality dental casts provided by Dr. Gildas Merceron. Mandibular data of extant Colobinae were extracted from virtual specimens provided by the Smithsonian Institution (Division of Mammals, USA); Harvard University (Museum of Comparative Zoology (MCZ), USA)); the Digital Morphology Museum (Primate Research Institute, Kyoto University) and the American Museum of Natural History (Department of Anthropology, USA). Humeral geometric cross-sectional properties were obtained on virtual specimens provided by the Harvard University (Museum of Comparative Zoology (MCZ), USA) and the Royal Museum of Central Africa (RMCA, Belgium).

  Type locality: Locality n°266 from the fossiliferous area of Toros-Menalla, western part of the Djurab desert, northern Chad basin. Type horizon: Anthracotherid Unit. Age: ca. 7 ± 0.2 Ma. Etymology: In honor of Pr. Michel Brunet for his significant contribution to paleoanthropology in Central Africa. Since 1994, he has initiated, led and directed the fieldwork of the Mission Paléoanthropologique Franco-Tchadienne (MPFT) in Chad. Specific diagnosis: A colobine of moderate size, similar in overall dental dimensions and inferred body mass to Paracolobus enkorikae (Lemudong'o Formation (Fm.), Kenya), Mesopithecus pentelicus, Libypithecus markgrafi (Wadi Natrun Fm., Egypt), colobine gen. and sp. A from Mpesida (Mpesida Beds, Tugen Hillas, Kenya) and colobine sp. B from Lower (LN) and Upper Nawata (UN) (Nawata Fm., Lothagam, Kenya).

C

  . bruneti is one of the smallest species of the East and South African genus Cercopithecoides, with dental dimensions similar to Cercopithecoides kerioensis, C. meavae, C. alemayehui and C. haasgati. It differs from the large taxa C. williamsi and C. kimeui in lacking a median mental canal and in possessing a gracile corpus.

  Mesopithecus a seed eating colobine? Assessment of cracking, grinding and shearing ability using dental topography. Journal of Human Evolution. 112, 79-92. Ting, N., 2008. Mitochondrial relationships and divergence dates of the African colobines: evidence of Miocene origins for the living colobus monkeys. Journal of Human Evolution. 55, 312-325. Williams, F.L., Geissler, E., 2014. Reconstructing the diet and paleoecology of Pli-Pleistocene Cercopithecoides williamsi from Sterkfontein, South Africa. PALAIOS. 29, 483-494. Youlatos, D., Koufos, G.D., 2010. Locomotor evolution of Mesopithecus (Primates: Colobinae) from Greece: evidence from selected astragalar characters. Primates. 51, 23-35. Youlatos, D., Couette, S., Koufos, G.D., 2012. A functional multivariate analysis of Mesopithecus (Primates: Colobinae) humeri from the Turolian of Greece. Journal of Human Evolution. 63, 219-230.

Figure captions Figure 1 .

 captions1 Figure captions

(

  A.) M 2 crown shape ratio (CSR) as M 2 PBL*100/MD with Colobus sspp. (n=50), Piliocolobus sspp. (n=16), Procolobus verus (n=12) and African fossil colobines. (B.) P 3-4 breadth differential (BD) as P 3 BL*100/P 4 BL with Colobus sspp. (n=45), Piliocolobus sspp. (n=16), Procolobus verus (n=12) and African fossil colobines (C.) Boxplot of the upper molars NH/NR ratio of C. bruneti (n=1; M 2 from TM 266 03-100), C. williamsi (n=1; M 1 from KB5277), M. pentelicus (n=3; M 2 from NHMW 1863, NHMW 1998, PK25), M 2 s from extant Cercopithecinae (n=8) and extant Colobinae (n=18).

Figure 2 .

 2 Figure 2. Digital photographs of C. bruneti maxillary remains. A.-N. TM 266 03-100 (A.-F.) left

Figure 3 .

 3 Figure 3. (A.) Comparative anatomy of Cercopithecoides spp. (i.e., C. bruneti and C. williamsi)

Figure 4 .

 4 Figure 4. Digital photographs of C. bruneti mandibular remains. A.-I. TM 219 01-102 (A.) occlusal

Figure 7 .

 7 Figure 7. Digital photographs of C. bruneti postcranial remains (i.e., TM 266 03-100 and TM 266

Figure 8 .

 8 Figure 8. Comparative anatomy of extant and extinct Colobinae forelimbs. (A.) C. guereza

Figure 9 .

 9 Figure 9. Postcranial indices of extant cercopithecids, C. bruneti and early colobines (i.e.,

  , extant Papio ssp. (n=26), extant Colobini (n=44) and extant Presbytini (n=38). (B.) Boxplot of the medial trochlear keel relative development of C. bruneti (n=1; TM 266 03-036), C. williamsi (n=1; KNM-ER 4420 with data from Frost and Delson, 2002), C. meavae (n=1; AL2-64 with data from Frost and Delson, 2002), M.

  Cercopithecoides williamsi Mollet, 1947. Generic diagnosis: As stated in[START_REF] Frost | Fossil Cercopithecidae from the Hadar Formation and surrounding areas of the Afar Depression, Ethiopia[END_REF]Medium to very large colobines with globular, rounded calvaria. The rostrum is short in comparison to neurocranial length, very different from Paracolobus, Rhinocolobus, Dolichopithecus, and Nasalis. It is not as short as that of Rhinopithecus, however. The frontal process of the zygomatic bone is narrow, unlike Paracolobus and Rhinocolobus. The inter-orbital region is broad, which is distinct from Libypithecus, Rhinocolobus, and Nasalis. The supraorbital tori are thick and separated from the calvaria by a deep ophryonic groove, which is distinct from Colobus, and most species of Presbytis and Trachypithecus. The calvaria itself lacks a sagittal crest, at least anteriorly, which separates it from Paracolobus and Procolobus. The P 3 lacks a protocone, which is similar to modern African colobines, but different from Libypithecus, Kuseracolobus, Paracolobus and Rhinocolobus. The mandibular symphysis is steep, but shallow and pierced by a median mental foramen (except in C. meaveae), which is different from all colobines other than Procolobus (Procolobus) and

	Suborder Anthropoidea Mivart, 1864;
	Infraorder Catarrhini E. Geoffroy, 1812;
	Superfamily Cercopithecoidea Gray, 1821;
	Family Cercopithecidae Gray, 1821;
	Subfamily Colobinae Blyth, 1863;
	genus Cercopithecoides Mollet, 1947.
	Type species:

Table 1 :

 1 Spatial and temporal setting of the Cercopithecoides representatives

		Type locality	Temporal record	Spatial record
	C. bruneti	Toros-Menalla, Chad, Central Africa.	ca. 7 Ma.	Only known from its type locality.
	C. kerioensis C. meavae	Lothagam, Kenya, East Africa. Leadu, Ethiopia, East Africa.	ca. 5-4.2 Ma. 1 3.8 -3.28 Ma. 2	Only known from its type locality. Hadar, Leadu, Woranso-Mille 2 .
	C. kimeui	Olduvai Gorge, Tanzania, East Africa	2.5-1.2 Ma.	Olduvai Gorge, Rawi, Koobi Fora,
	C. haasgati	Haasgat, South Africa.	?Pleistocene. 3	Hadar. Only known from its type locality.
	C. williamsi	Makapansgat, South Africa.	3.5-1.5 Ma.	Makapansgat, Sterkfontein,
				Swarktrans, Cooper's A, Bolt's
				Farm, Kromdraai, Drimolen, Koobi
				Fora, ?Shungura, Leba (Angola).
	C. alemayehui	Daka, Ethiopia, East Africa.	1.0 Ma.	Only known from its type locality.
	C. sp. indet. Laetoli	Laetoli, Tanzania, East Africa.	3.81-3.63 Ma.	Uncertain taxonomy and known
				only from Laetoli.
	cf. C. sp. indet. Koobi Fora	Koobi Fora, Ethiopia, East Africa.	3.95-3.45 Ma.	Uncertain taxonomy and known only from Allia Bay 4 .
	i C. sp. indet. Kanapoi	Kanapoi, Kenya, East Africa	4.19-4.11 Ma.	Uncertain taxonomy and known
				only from Kanapoi.

Table 2 :

 2 Comparative morphology of the cranio-dental anatomy of Cercopithecoides spp.

	Range values of odontometric indices and qualitative assessment of several morphological characteristics of Cercopithecoides
	spp. With Body Mass (BM); Crown Shape Ratio (CSR); Breadth Differential (BD); Relative Hypolophid Development (RHD);
	Maxillary Sinuses (MS); Superior Transverse Torus (STT); Inferior Transverse Torus (ITT); Corpus Width (CW); Not Available
	(NA).

1

Based on the equation provided by

[START_REF] Delson | Body mass in Cercopithecidae (Primates, Mammalia) : Estimation and scaling in extinct and extant taxa[END_REF]

2 Calculated from M 1 MD dimension with "All-colobine" model parameters.

3 Range value calculated from M 2 MD dimension with "All-colobine" model parameters.

4

Values given in

[START_REF] Delson | Body mass in Cercopithecidae (Primates, Mammalia) : Estimation and scaling in extinct and extant taxa[END_REF]

for the "Estimated mass " value. 5 Calculated from M 2 MD dimension with "All-colobine" model parameters.

6 Range value alculated from M 2 MD dimension with "All-colobine" model parameters on minimum and maximum dental dimensions provided in

McKee et al., 2011. 7

Ratio calculated from mean dental dimensions provided in

McKee et al., 2011. 8

Table 3 :

 3 C. bruneti holotype (i.e TM 266 03-100) dental metrics

	Measurements
	dP 3 MD 1	5.6 (5.5)	P 3 MD 2	6.0 (5.9)
	dP 3 BL 1	5.4 (5.3)	P 3 BL 2	6.1 (6.1)
	dP 4 MD 1	7.1 (6.8)	P 4 MD 2	6.0 (6.1)
	dP 4 PBL 1	6.8 (6.8)	P 4 BL 2	7.8 (7.9)
	dP 4 MBL 1	6.6 (6.3)	M 1 MD 1	7.5 (7.8)
	C 1 MD 2	8.4 (8.6)	M 2 MD 1	8.3
	C 1 BL 2	5.2 (5.3)	M 2 MBL 1	9.4

Table 4 :

 4 Dental metrics and dental indices of C. bruneti lower dentition (i.e TM 266 03-099; TM 112 00-093; TM 219 01-102)

	Measurement	TM 266 03-099	TM 112 00-093	TM 219 01-102
	C1 MD	~5.4	~4.3 (~4.4)	6.7
	C1 BL	~8.5	~5.2 (~5.3)	8.9 (9.1)
	P3 OL	(7.6)	4.8
	P3 TL	(10.2)	6.8	9.4
	P3 FL	(7.7)	6.3
	P3 BL	(4.2)	3.2
	P4 MD	6.1	5.5	6.3
	P4 BL	4.4
	M1 MD	6.9	6.6	7.5
	M1 MBL	5.7
	M1 HBL	5.6
	M2 MD	7.7	7.1	7.9
	M2 MBL	6.8
	M2 HBL	6.4
	M3 MD	10.3	8.8
	M3 HBL	6.5
	M3 HYPOB	3.1
	M3 HYPOB/HBL	47.9
	M3 HBL/MD	63.4
	P4 BL/MD	73.0
	M1-2 SD	75.5
	P3 BL/OL	55.2	65.8

Table 5 :

 5 Mandibular morphometry of C. bruneti hypodigmMorphometric data in mm. All measurements taken on selected photographs of symphyseal and corporeal cross section obtained through Avizo and Geomagic and measured through ImageJ. SL: symphyseal length; SA: symphyseal angle; GFH: genioglossal fossa height; PAL: planum alveolare length; SB: maximum breadth of the symphysis; SBSTT: breadth of the symphysis at the STT (superior transverse torus) level; SBITT: breadth of the symphysis at the ITT (inferior transverse torus) level; CWM1: corpus width at mid-M1; CLM1: corpus length at mid-M1. For an extended description of the morphometric protocol, refers to SOM FigureS1.

		TM 266 03-099	TM 112 00-093	TM 219 01-102
	SL	26.7	20.8	27.5
	SA	63.4	62	62.6
	GFH		7.9	27.5
	PAL	11.3	11.3	27.5
	SB	12.3	9.7	27.5
	SBSTT	11.3	9.7	27.5
	SBITT	12.3	7.6	27.5
	CWM1	26.7	18.8	27.5
	CLM1	10.5	7.5	27.5

Table 6 :

 6 C. bruneti postcranial morphometric data

According toLeakey et al.,

2003, there is no secure stratigraphic context relative to C. kerioensis. 2 It includes here specimens from Woranso-Mille and allocated to C. cf. meavae. 3 According to McKee et al., 2011, there is uncertainty relative to the exact temporal setting of the Cercopithecoides sample from Haasgat 4 According to Jablonski et al., 2008, a partial mandible, KNM-ER 36985, exhibit phenetic affinities with C. kerioensis but the authors referred to this specimen as C. sp. indet. 5 Uncertain age estimation based on faunal assemblage(Jablonski, 1994)

Acknowledgements

We are grateful to the Chadian authorities and to the Ministère en charge de l'Enseignement Supérieur et de la Recherche, N'Djamena (CNRD ex-CNAR and Université de N'Djamena), to all the members of the field surveys and excavations lead by the MPFT (P.I. M. Brunet) and to the Ambassade de France (Commission des Fouilles, Paris et Ambassade de France à N'Djamena).

We acknowledged the contribution of M. Adoum, D. Merci and Dr. C. D. Nekoulnang. We thank S. Riffaut, X. Valentin, G. Renaud, M. Pourade, Dr. A. Mazurier, J. Surault and A. Walker for technical support and administrative guidance. We are grateful to Dr. G. Merceron and Dr. G.

Thiery for fruitful scientific discussion. We thank the Smithsonian's Division of Mammals (Dr.

Kristofer Helgen) and Human Origins Program (Dr. Matt Tocheri) for the scans of USNM specimens used in this research. These scans were acquired through the generous support of the Smithsonian 2.0 Fund and the Smithsonian's Collections Care and Preservation Fund. We also thank the Museum of Comparative Zoology of the Harvard University, Lynn Lucas and Lynn

Copes as well as the Wenner Gren Foundation for providing access to their virtual data, deposited on www.MorphoSource.org, Duke University. We are grateful to Dr. Eric Delson and the AMNH Department of Mammalogy for providing access to their data, the collection of which was funded by AMNH and NYCEP and deposited on www.MorphoSource.org, Duke University.

We also express gratitude to Dr. Justin W. Adams who collaborated with the Plio-Pleistocene Section of the Ditsong National Museum of Natural History to provide us access to these data originally appearing in [START_REF] Adams | Surface model and tomographic archive of fossil primate and other mammal holotype and paratype specimens of the Ditsong National Museum of Natural History, Pretoria, South Africa[END_REF]