Amélie Beaudet

Jean Dumoncel

Frikkie De Beer

Benjamin Duployer

Stanley Durrleman

Emmanuel Gilissen

Jakobus Hoffman

Christophe Tenailleau

John Francis Thackeray

José Braga

Morphoarchitectural variation in South African fossil cercopithecoid endocasts

Keywords: Endocranial organization, Old World monkey taxonomy, Deformation-based models, Plio-Pleistocene, Theropithecus, Cercopithecoides

Despite the abundance of well-preserved crania and natural endocasts in the South African Plio-Pleistocene cercopithecoid record, which provide direct information relevant to the evolution of their endocranial characteristics, few studies have attempted to characterize patterns of external brain morphology in this highly successful primate Superfamily. The availability of non-destructive penetrating radiation imaging systems, together with recently developed computer-based analytical tools, allow for high resolution virtual imaging and modelling of the endocranial casts and thus disclose new perspectives in comparative paleoneurology. Here, we use X-ray microtomographic-based 3D virtual imaging and quantitative analyses to investigate the endocranial organization of 14 cercopithecoid specimens from the South African sites of Makapansgat, Sterkfontein, Swartkrans, and Taung. We present the first detailed comparative description of the external neuroanatomies that characterize these Plio-Pleistocene primates. Along with reconstruction of endocranial volumes, we combine a semi-automatic technique for extracting the neocortical sulcal pattern together with a landmark-free surface deformation method to investigate topographic differences in morphostructural organization. Besides providing and comparing for the first time endocranial volume estimates of extinct Plio-Pleistocene South African cercopithecoid taxa, we report additional information regarding the variation in the sulcal pattern of Theropithecus oswaldi subspecies, and notably of the central sulcus, and the neuroanatomical condition of the colobine taxon Cercopithecoides williamsi, suggested to be similar for some aspects to the papionin pattern, and discuss potential phylogenetic and taxonomic implications. Further research in virtual paleoneurology, applied to specimens from a wider geographic area, is needed to clarify the polarity, intensity, and timing of cortical surface evolution in cercopithecoid lineages.

Introduction

Recent research employing three dimensional (3D) imaging techniques has provided important insights into the brain organization of early cercopithecoids and hence Old World monkeys as a whole [START_REF] Gonzales | Cerebral complexity preceded enlarged brain size and reduced olfactory bulbs in Old World monkeys[END_REF]. However, relatively little is known about patterns of cercopithecoid brain evolution more generally, despite the extensive Plio-Pleistocene fossil record. The handful of previous studies has focused mainly on one genus, Theropithecus [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF][START_REF] Elton | Comparative context of Plio-Pleistocene hominin brain evolution[END_REF], or estimating endocranial volume (ECV; e.g. [START_REF] Martin | Allometric aspects of skull morphology in Theropithecus[END_REF], although more recent work has highlighted the potential utility of examining the internal morphostructure of Plio-Pleistocene cercopithecoids [START_REF] Beaudet | Caractérisation des structures crânio-dentaires internes des cercopithécoïdes et étude diachronique de leurs variations morphologiques dans la séquence Plio-Pléistocène sud-africaine[END_REF][START_REF] Beaudet | A new cercopithecoid dentognathic specimen attributed to Theropithecus from the late Early Pleistocene (c. 1 Ma) deposits of Simbiro, at Melka Kunture, Ethiopian highlands[END_REF][START_REF] Beaudet | Neutron microtomography-based virtual extraction and analysis of a cercopithecoid partial cranium (STS 1039) embedded in a breccia fragment from Sterkfontein Member 4 (South Africa)[END_REF]. In part, the lack of attention has been because of a paucity of natural endocasts plus methodological limitations in studying cranial material, notwithstanding its abundance.

Fortunately, recent advances in the use of high-resolution 3D imaging and computer-assisted analytical approaches have provided the means with which to examine, in much more detail, cranial material from the extensive Old World monkey fossil record and hence fill important gaps in our knowledge of cercopithecoid brain evolution.

The Plio-Pleistocene cercopithecoid record of South Africa samples at least seven cercopithecoid genera and up to twelve species, with fossil material including several complete skulls and/or nearly intact natural endocasts [START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF][START_REF] Szalay | Evolutionary History of the Primates[END_REF][START_REF] Delson | Cercopithecoid biochronology of the African Plio-Pleistocene: correlation among eastern and southern hominid-bearing localities[END_REF][START_REF] Delson | Chronology of South African australopiths site units[END_REF][START_REF] Jablonski | Fossil Old World monkeys: the late Neogene radiation[END_REF][START_REF] Gilbert | Craniomandibular morphology supporting the diphyletic origin of mangabeys and a new genus of the Cercocebus/Mandrillus clade, Procercocebus[END_REF][START_REF] Gilbert | Cladistic analysis of extant and fossil African papionins using craniodental data[END_REF][START_REF] Mckee | New species of Cercopithecoides from Haasgat, North West Province, South Africa[END_REF]. Three Parapapio species are currently recognised in South Africa (Parapapio broomi, Parapapio jonesi, and Parapapio whitei) plus the "Parapapio" morph identified at Taung and originally attributed to Parapapio antiquus [START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF][START_REF] Szalay | Evolutionary History of the Primates[END_REF], along with three extinct variants of Papio: Papio angusticeps, Papio izodi, and Papio robinsoni [START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF][START_REF] Delson | Cercopithecoid biochronology of the African Plio-Pleistocene: correlation among eastern and southern hominid-bearing localities[END_REF][START_REF] Mckee | Taxonomic and evolutionary affinities of Papio izodi fossils from Taung and Sterkfontein[END_REF][START_REF] Mckee | Craniodental remains of Papio angusticeps from the Haasgat cave site, South Africa[END_REF]. All the Parapapio taxa (including some material attributed to Pp. antiquus) plus P. izodi contain specimens for which endocranial morphology can be assessed. Theropithecus oswaldi is also found in South Africa, divided into three chronosubspecies (from oldest to youngest): Theropithecus oswaldi darti, Theropithecus oswaldi oswaldi, and Theropithecus oswaldi leakeyi [START_REF] Leakey | Evolution of Theropithecus in the Turkana Basin[END_REF][START_REF] Frost | Fossil Cercopithecidae from the Hadar Formation and surrounding areas of the Afar Depression, Ethiopia[END_REF][START_REF] Frost | Fossil Cercopithecidae from the Middle Pleistocene Dawaitoli Formation, Middle Awash Valley, Afar Region, Ethiopia[END_REF]. Although Plio-Pleistocene Theropithecus brain evolution has been the subject of previous work [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF][START_REF] Elton | Comparative context of Plio-Pleistocene hominin brain evolution[END_REF], sampling the T. o. darti material from Makapansgat is particularly relevant as it was not included in Falk's seminal 1981 study of sulcal patterning and its implications for function and evolutionary history. Aspects of endocranial form can also be studied in T. o. oswaldi from Swartkrans, but unfortunately not in two further large-bodied papionin taxa, Dinopithecus ingens and Gorgopithecus major, as they are represented mainly by fragmentary remains [START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF][START_REF] Delson | Cercopithecoid biochronology of the African Plio-Pleistocene: correlation among eastern and southern hominid-bearing localities[END_REF][START_REF] Jablonski | Fossil Old World monkeys: the late Neogene radiation[END_REF][START_REF] Jablonski | Cercopithecoidea[END_REF]. The same is true for specimens from Kromdraai, Makapansgat, and Swartkrans that have been assigned to Cercocebus sp. [START_REF] Eisenhart | The fossil cercopithecoids of Makapansgat and Sterkfontein[END_REF][START_REF] Delson | Cercopithecoid biochronology of the African Plio-Pleistocene: correlation among eastern and southern hominid-bearing localities[END_REF][START_REF] Delson | Chronology of South African australopiths site units[END_REF]). However, it is possible to examine Cercopithecoides williamsi, one of two extinct colobine species (the other being Cercopithecoides haasgati) recognized in the South African Plio-Pleistocene [START_REF] Delson | Cercopithecoid biochronology of the African Plio-Pleistocene: correlation among eastern and southern hominid-bearing localities[END_REF][START_REF] Delson | Chronology of South African australopiths site units[END_REF][START_REF] Jablonski | Fossil Old World monkeys: the late Neogene radiation[END_REF][START_REF] Mckee | New species of Cercopithecoides from Haasgat, North West Province, South Africa[END_REF], which provides insight into the colobine as well as the cercopithecine radiation. The fossil monkeys from South Africa are therefore an appropriate and suitably diverse group on which new methodological advances can be applied to increase our knowledge of cercopithecoid brain evolution. Knowledge of primate brain evolution is based both on comparative information from living species whose brains and behavior can be directly investigated [START_REF] Armstrong | Primate Brain Evolution. Methods and Concepts[END_REF] and the interpretation of paleoneurological evidence. To date, much of that paleoneurological evidence has come from the study of endocasts. Fossil endocasts consist of replicas of the internal table of the bony braincase and provide the only direct evidence of brain evolution. When the neurocranium is filled with sediment during fossilization, morphological information about the external brain surface may be preserved as a natural endocast, as illustrated in the South African primate fossil record [START_REF] Brain | The Hunters of the Hunted? An introduction to African Cave Taphonomy[END_REF][START_REF] Holloway | The Human Fossil Record: Brain Endocasts, the Paleoneurological Evidence[END_REF]. Endocasts constitute a proxy for investigating and quantifying variations in brain size, global brain shape, and neocortical surface morphology, including imprints of cerebral convolutions (i.e., gyri and sulci; [START_REF] Holloway | The relevance of endocasts for studying primate brain evolution[END_REF][START_REF] Holloway | The Human Fossil Record: Brain Endocasts, the Paleoneurological Evidence[END_REF][START_REF] Falk | Interpreting sulci on hominin endocasts: old hypotheses and new findings[END_REF][START_REF] Neubauer | Endocasts: possibilities and limitations for the interpretation of human brain evolution[END_REF]. Given the intimate relationships and patterns of co-variation between brain growth and development and its neurocranial bony container, endocasts are suitable proxies when assessing original brain size and morphological details. Recent comparisons between endocranial organization in the brain and endocranial virtual replicas of primate individuals support the close correspondence between endocranial impressions and cerebral sulci and gyri (e.g., [START_REF] Kobayashi | Cerebral sulci and gyri observerd on macaque endocasts[END_REF].

Following pioneering research in defining the several levels of evidence that can be collected from endocasts, including gross brain size, delineation of cerebral areas, and major sulcal and gyral identifications [START_REF] Holloway | The relevance of endocasts for studying primate brain evolution[END_REF], availability of non-destructive penetrating radiation imaging systems, together with recently developed computer-based analytical tools, have allowed for high resolution virtual imaging and modelling of endocranial casts, thus disclosing new perspectives in comparative paleoneurology (Zollikofer and Ponce de León, 1998;[START_REF] Zollikofer | A computational approach to paleoanthropology[END_REF][START_REF] Gunz | Principles for the virtual reconstruction of hominin crania[END_REF][START_REF] Weber | Virtual Anthropology: a guide to a new interdisciplinary field[END_REF]. Digital data make the quantitative analysis of overall endocranial shape possible, notably through geometric morphometric methods [START_REF] Bruner | Encephalization and allometric trajectories in the genus Homo: evidence from the Neandertal and modern lineages[END_REF][START_REF] Bruner | Landmark-based analysis of the morphological relationship between endocranial shape and traces of the middle meningeal vessels[END_REF][START_REF] Bruner | Human midsagittal brain shape variation: patterns, allometry and integration[END_REF][START_REF] Bruner | Geometric morphometrics and paleoneurology: brain shape evolution in the genus Homo[END_REF][START_REF] Neubauer | The pattern of endocranial ontogenetic shape changes in humans[END_REF][START_REF] Neubauer | Endocranial shape changes during growth in chimpanzees and humans: a morphometric analysis of unique and shared aspects[END_REF][START_REF] Gunz | Computed tools for paleoneurology[END_REF] and registration of surfaces from the correspondence of anatomical landmarks [START_REF] Specht | Visualizing shape transformation between chimpanzee and human braincases[END_REF]. However, the use of a traditional methodological toolkit based on landmarks, semilandmarks, and curves, even if efficient in compartmentalizing the endocranial cavity, captures little information about the brain itself and its subdivisions. One potential compromise thus proposed in this study is to combine a detailed analysis of sulcal pattern via automatic detection of the neocortical surface together with the characterization of overall endocranial shape via deformation based-models (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 | Caractérisation des structures crânio-dentaires internes des cercopithécoïdes et étude diachronique de leurs variations morphologiques dans la séquence Plio-Pléistocène sud-africaine[END_REF]. We also aim to show that the different types of evidence available from endocasts and described by [START_REF] Holloway | The relevance of endocasts for studying primate brain evolution[END_REF] can be accessed and assessed reliably for South African fossil cercopithecoid endocrania by means of advanced methods of high-resolution 3D imaging and computer-assisted analytical approaches.

In this paper, along with furthering the development of methods for visualizing and quantifying sulcal pattern and endocranial shape, we report new estimates of ECV (a reliable estimate of actual brain size; [START_REF] Isler | Endocranial volumes of primate species: scaling analyses using a comprehensive and reliable data set[END_REF] for eight South African cercopithecoid taxa.

We also consider the implications of our data on endocranial morphology for improving knowledge of the South African cercopithecoid fossil record, including the taxonomy and evolutionary history of Plio-Pleistocene monkeys, that may be derived from study of sulcal patterns and global shape. We are particularly interested in examining two main issues: (1) variation in sulcal pattern in Theropithecus, and (2) the endocranial morphology of C. williamsi. [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF] noted distinct features in the sulci of T. o. oswaldi, specifically a 'hooklike' configuration of the central sulcus, which was not evident in T. gelada, and by extending the sample to South African fossils, we explore variation and divergence in the Theropithecus lineage further, which in turn gives clues to the evolutionary history of that highly successful and widespread Plio-Pleistocene radiation. Other work on sulcal patterning [START_REF] Connolly | External Morphology of the Primate Brain[END_REF][START_REF] Radinsky | The fossil evidence of anthropoid brain evolution[END_REF][START_REF] Falk | Brain evolution in Old World Monkeys[END_REF] has also highlighted taxon-based gross sulcal patterning, for example discriminating between colobines and cercopithecines. Further examination of possible cercopithecine / colobine distinctions is especially interesting given the presence of C. williamsi in the South African Plio-Pleistocene fossil monkey assemblage: despite a typical colobine dental morphology and pollical reduction indicating membership of the extant African colobine clade [START_REF] Delson | Evolutionary history of the Cercopithecidae[END_REF][START_REF] Szalay | Evolutionary History of the Primates[END_REF][START_REF] Frost | The hand of Cercopithecoides williamsi (Mammalia, Primates): earliest evidence for thumb reduction among colobine monkeys[END_REF], the locomotor and dietary behavior of C. williamsi, along with its large size, is consistent with a terrestrial lifestyle that differs substantially from the arboreal existence observed in its living counterparts [START_REF] Birchette | Postcranial remains of Cercopithecoides[END_REF][START_REF] Leakey | Extinct large colobines from the Plio-Pleistocene of Africa[END_REF][START_REF] Codron | Utilization of savanna-based resources by baboons during the Plio-Pleistocene[END_REF] and in many ways seems quite papionin-like. Quantifying its endocranial morphology thus helps to build a fuller picture of this fascinating animal.

Material and methods

Sample

Our fossil sample includes 14 specimens from four South African Plio-Pleistocene sites (Makapansgat [Member 4], Sterkfontein [Member 4], Swartkrans [Member 1], and Taung; [START_REF] Brain | The Hunters of the Hunted? An introduction to African Cave Taphonomy[END_REF][START_REF] Heaton | Taxonomy of the Sterkfontein fossil Cercopithecinae: the Papionini of Members 2 and 4 (Gauteng, South Africa)[END_REF], detailed in Table 1.

Our comparative sample of extant specimens (n = 46) comprises 11 cercopithecoid genera with both sub-adult and adult individuals (dental age ranging from M3 crown completion to complete emergence and root apical closure; Table 1). Given that the M1 emergence occurs near the time of the cessation of neural growth [START_REF] Smith | Dental development and the evolution of life history in Hominidae[END_REF] and that the main cerebral developmental processes (i.e., corticogenesis) are observed in utero or early in the post-natal period in cercopithecine primates [START_REF] Fukunishi | Development of cerebral sulci and gyri in fetuses of cynomolgus monkeys (Macaca fascicularis)[END_REF][START_REF] Malkova | Longitudinal magnetic resonance imaging study of rhesus monkey brain development[END_REF][START_REF] Kashima | Development of cerebral sulci and gyri in fetuses of cynomolgus monkeys (Macaca fascicularis). II. Gross observation of the medial surface[END_REF][START_REF] Sawada | Developments of sulcal pattern and subcortical structures of the forebrain in cynomolgus monkey fetuses: 7-tesla magnetic resonance imaging provides high reproducibility of gross structural changes[END_REF], we assume that the endocasts extracted in our sample are directly comparable.

Scanning protocol and endocast reconstruction

All of the specimens investigated in this study have been detailed by micro-focus X-ray tomography (µCT) using various systems detailed in Table 1, except for one of the Mandrillus individuals detailed by cone beam computed tomography (CBCT) with a spatial resolution of 200 µm because of its large dimensions. The isometric voxel size of the reconstructed volumes ranges from 32.7 to 200 µm (Table 1).

The virtual extraction and reconstruction of endocrania were performed through two distinct protocols. In the case of fossil specimens, with the exception of SK 561, the sediments filling the endocranial cavity were digitally separated from the bony remains through semi-automatic threshold-based segmentation via the Avizo v8.0 software (Visualization Sciences Group Inc.). The virtual endocranial volumes were extracted from the representatives of the extant genera and the fossil specimen SK 561 by using the Endex software [START_REF] Subsol | 3D automatic methods to segment ''virtual'' endocasts: state of the art and future directions[END_REF]; http://liris.cnrs.fr/gilles.gesquiere/wiki/doku.php?id=endex).

Taphonomic processes and virtual reconstruction

In our fossil sample, six specimens were affected by taphonomic processes and virtually reconstructed (Supplementary Online Material [SOM] Figs. S1-S2 and related comments in SOM Material and methods). On the whole, the observed diagenetic damages were classified into three categories. First, in the neurocrania of STS 565,MP 221,MP 222,and MP 224, part of the cranial vault is missing, creating a significant hole in the endocranial surface (SOM Figs. S1-S2). Based on the morphology of the available bony parts, the non-preserved regions were artificially and automatically closed by digitizing a curve network around the margin of the missing area and by creating a non-uniform rational basis-spline (NURBS) surface that matched the points along the curves through the Rhino v5.0 software (R. McNeel & Associates;[START_REF] Benazzi | A new OH5 reconstruction with an assessment of its uncertainty[END_REF]. The second category concerns the specimen STS 564, which lacks the left hemisphere (SOM Figs. S1-S2). In order to generate a complete volume, the well preserved right side was mirrored to artificially reconstruct the opposite side [START_REF] Gunz | Principles for the virtual reconstruction of hominin crania[END_REF]. Finally, the last category refers to the specimen TP 8, in which a fissure separates the endocranial filling in two distinct parts that were virtually stitched together (SOM Figs S1- S2).

Endocranial volumes

Endocranial volumes (ECV) were assessed in 51 extant and fossil cercopithecoid specimens identified at the species level. Measurements of ECV have been computed from the unsmooth 2D segmentation labels ("Material statistics" module available on Avizo v8.0).

For damaged fossils (i.e., STS 564,STS 565,MP 221,MP 222,MP 224), reconstructed surfaces were used in analysis (SOM Figs S1-S2). Given the allometric relationship between ECV and body mass in primates [START_REF] Isler | Endocranial volumes of primate species: scaling analyses using a comprehensive and reliable data set[END_REF], logged (base 10) ECV values were plotted against logged (base 10) body mass estimates, with body mass estimates derived from Smith and Jungers (1997), [START_REF] Delson | Body mass in Cercopithecidae (Primates, Mammalia): estimation and scaling in extinct and extant taxa[END_REF], and [START_REF] Scott | Folivory, frugivory, and postcanine size in the Cercopithecoidea revisited[END_REF]. We consider our ECV analyses to be exploratory and preliminary since aspects such as phylogenetic regression and allometry will not be discussed here.

Deformation-based models

To compare endocranial morphology between species, we used a landmark-free method that relies on the calculation of group-average surface models and their deformation onto the investigated surfaces (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] Dumoncel | How to Build an Average Model When Samples Are Variably Incomplete? Application to Fossil Data[END_REF][START_REF] Beaudet | Caractérisation des structures crânio-dentaires internes des cercopithécoïdes et étude diachronique de leurs variations morphologiques dans la séquence Plio-Pléistocène sud-africaine[END_REF]. The deformation-based models differ substantially from geometric morphometrics methods because (i) they are not based on prior definition of homologous points but on correspondences between continuous surfaces and (ii) statistics are not performed on the positions of individual points but on deformations (see Durrleman et al., 2012a for further details). Examining deformations between surfaces, mathematically modeled as a "diffeomorphism," is particularly appropriate for comparing overall shapes and local orientation in the field of computational anatomy (Glaunès and Joshi, 2006;[START_REF] Durrleman | Morphometry of anatomical shape complexes with dense deformations and sparseparameters[END_REF].

The overall process includes several successive computational steps, illustrated in Figure 1. As a pre-processing step, the surfaces were rigidly aligned in position, orientation, and scale with respect to a reference surface (randomly selected) using the iterative closest point (ICP) algorithm (Fig. 1A). Second, a shape model, called global mean shape (GMS), is computed from the set of aligned surfaces. The construction is done using an iterative optimization algorithm described in [START_REF] Durrleman | Statistical Models of Currents for Measuring the Variability of Anatomical Curves, Surfaces and their Evolution[END_REF], which uses an ellipsoid surface as input (Fig. 1B) and yields the GMS as output (Fig. 1C). The algorithm also yields deformation fields, which are the parameters of non-linear deformations registering the GMS to each specimen. They are distributed in a 3D grid enclosing the surfaces and common to all the registrations procedures between the GMS and the specimens (see Durrleman, 2010 for further technical details; Fig. 1C). In our analyses, because the fossil specimens may be taphonomically deformed, GMS was estimated using the extant specimens only. Additionally, based on the results provided by the third step, a taxon mean shape (TMS) was computed for each extant taxon represented in our sample (Fig. 1D). Finally, the Plio-Pleistocene specimens were included in the analysis and the GMS was deformed to each individual (Fig. 1E).

Based on the deformation framework, we generated (i) a GMS associated with a set of deformations from the GMS to each endocranium (hereinafter called "GMS-to-individuals") computed from our extant sample, (ii) a TMS for each extant genus investigated in our study and represented by more than two individuals, and (iii) deformations from the GMS to fossil endocasts. In addition to GMS-to-individuals deformations, the GMS was also deformed to the TMS (hereinafter called "GMS-to-TMS").

The magnitude of the displacements recorded during the deformation process (i.e., GMSto-individuals and GMS-to-TMS) were rendered by color maps from dark blue (lowest displacement values) to red (highest displacement values) on the endocast surfaces (i.e., TMS and individual endocasts; Fig. 1E). In combination with the cartographies, the directions and magnitudes of the deformations from the GMS to the TMS/individuals are represented by vectors (Fig. 1E).

Semi-automatic sulci detection

Some cortical details, including the sulcal imprints, were evident in most of the fossil specimens (SOM Figs. S1-S2). Sulcal pattern is usually identified and described by visual inspection of the endocranial surface. Based on previous studies [START_REF] Subsol | Construction automatique d'atlas anatomiques morphométriques à partir d'images médicales tridimensionnelles[END_REF][START_REF] Subsol | Crest lines for curve based warping[END_REF], we here use an automatic method for the identification of neocortical relief in endocasts that includes the algorithm presented by [START_REF] Yoshizawa | Fast and faithful geometric algorithm for detecting crest lines on meshes[END_REF][START_REF] Yoshizawa | Fast, robust, and faithful methods for detecting crest lines on meshes[END_REF] for the detection of topographical variations (i.e., crest lines) in 3D meshes. The sulci are considered to be variation points of the surface on a triangle mesh and detected via a geometry-based method using curvature lines computed on the surface. More precisely, the crest lines are defined as salient subsets of the extrema of the principal curvatures on surfaces. The detected structures were corrected manually by removing the non-anatomical features (e.g., cracks due to taphonomic damage), using "The Primate Brain Bank" (www.primatebrainbank.org) and published studies of cercopithecoid endocasts as references (e.g., [START_REF] Connolly | External Morphology of the Primate Brain[END_REF][START_REF] Falk | Brain evolution in Old World Monkeys[END_REF][START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF]. This "cleaning" step was performed using a program created with MATLAB R2013a v8.1 (Mathworks) by one of us (J.D.).

Multivariate analyses

The deformation fields integrating local orientation and the amplitude of the deformations from the GMS to each specimen (i.e., GMS-to-individuals) were statistically analyzed by computing a between-group principal component analysis (bgPCA; [START_REF] Durrleman | Statistical Models of Currents for Measuring the Variability of Anatomical Curves, Surfaces and their Evolution[END_REF][START_REF] Mitteroecker | Linear discrimination, ordination, and the visualization of selection gradients in modern morphometrics[END_REF]. Based on the covariance matrix of the predefined extant group means, the fossil specimens were subsequently projected into the shape space. Shape changes and morphological trends observed in the specimens/clusters plotted were depicted by color maps and vectors.

A hierarchical clustering on principal components (HCPC) tree, integrating all the bgPCA components, was generated using the FactoMineR package [START_REF] Lê | FactoMineR: an R package for multivariate analysis[END_REF] for R v.3.2.1 (R Development Core Team, 2015).

Results

Endocranial volumes

The endocranial volumes measured for both extant and fossil cercopithecoid specimens are presented in Table 2 and plotted against body mass in Figure 2. Of these species, Chlorocebus, Erythrocebus, and Cercopithecus have the smallest ECVs relative to body mass. Taking their "medium" body masses into account, the mangabeys Cercocebus and Lophocebus have relatively larger endocranial capacities than do the colobines Colobus and Piliocolobus. Most of the living papionins plot on the upper range of the ECV estimates, with Papio having the largest ECV relative to body mass. On the contrary, the Macaca individuals are distributed toward the lower estimates of the papionin cluster. All the fossil specimens fall within or close to the lower limit of extant papionin variation, even C. williamsi, which lies closer to extinct Theropithecus than to extant colobines.

Morphoarchitectural variation

The bgPCA analysis of endocast deformations is shown in Figure 3 The T. o. oswaldi specimen SK 561 is relatively close to the extant representatives of this genus in the bgPCA (Fig. 3). These affinities are explained by the elevation of the superior parietal surface and by the reduction of the temporal lobes (Fig. 5 and SOM Fig. S3).

However, the vectors oriented inferiorly, strongly marked, suggest potential diagenetic williamsi and included in extant colobine variability in the bgPCA, is shared with extant colobines (Fig. 5 and SOM Fig. S3). On the contrary, the two other C. williamsi specimens, MP 36 and MP 3a, are closer to the fossil papionins than to the extant colobines. MP 3a shares temporal lobe reduction with living colobines as illustrated by the vectors oriented ventro-dorsally (Fig. 5 and SOM Fig. S3), although it also has substantial contraction of the left occipital lobe.

The HCPC computed on the results of the deformation process is shown in Figure 6. As for the bgPCA, our sample is roughly divided into three main clusters corresponding to the tribes Papionini, Colobini, and Cercopithecini. Among the Papionini, the extant representatives of Papio (Fig. 6, group G) and Mandrillus (Fig. 6, group F) are clearly separated from the other members of the tribe, in accordance with the specific morphology depicted by the color maps and the vectors (SOM Fig. S3). The affinities of SK 561 with extant Theropithecus are supported by its inclusion among the geladas, and so is the relationship between M 3055 and the extant colobines. As previously mentioned, MP 222 is close to Macaca, but the influence of the reconstructed cranial vault needs to be clarified. Interestingly, the majority of the fossil specimens are included in groups D and E of Figure 6, which separate the specimens of Makapansgat from the specimens of Sterkfontein and Taung, independent of individual taxonomic affiliation. The Makapansgat group also includes the Lophocebus specimens.

According to the deformation maps (Figs. 4-5 and SOM Fig. S3), the shift of the occipital lobes to an inferior position is combined with an elongation of the frontal pole for the Makapansgat specimens, contributing to a relatively straighter overall profile than the Sterkfontein and Taung specimens, which are more globular.

Sulcal pattern

The extant cercopithecoid sulcal condition, including members of the cercopithecin, papionin, and colobinan tribes, is represented by selected specimens in SOM Figures S4-S5 and described in related comments (SOM Results). In summary, the basic cercopithecine sulcal pattern that we observed in this sample corresponds to the previous descriptions of [START_REF] Connolly | External Morphology of the Primate Brain[END_REF] and [START_REF] Falk | Brain evolution in Old World Monkeys[END_REF]. One of the most critical neocortical features that helps discriminate the colobine brain (both African and Asian) from the cercopithecine cerebral condition is the presence of paroccipital sulcus [START_REF] Falk | Brain evolution in Old World Monkeys[END_REF]. Unfortunately, because of relatively faint sulcal imprints in the parietal and occipital regions of endocasts, we were not able to detect this critical structure in our endocasts.

Results of the automatic detection of neocortical sulci in the fossil sample are illustrated in While the principal sulcus position in T. o. darti is close to the papionin pattern (Fig. 8), the arcuate sulcus is relatively curved, as in colobines (SOM Fig. S5). The subcentral anterior sulcus is identified on the right hemisphere of M 3073 and is connected to the arcuate sulcus.

The subcentral posterior sulcus on the left hemisphere of M 3073 is linked with the central sulcus, whereas the central sulcus curves sharply in a caudal direction in the right hemisphere ('hook-like' configuration). The intraparietal and lunate sulci are relatively straight and the inferior occipital sulcus is identified only on the left hemisphere in the case of M 3073.

For C. williamsi, except in the left hemisphere of M 3055, the lateral and temporal superior sulci converge but do not intercept, in a similar fashion to Colobus. The frontal sulcal pattern in C. williamsi specimens MP 3a and MP 36 is similar to that of the extant papionins, based on the presence of relatively straight grooves and the divergence of the principal sulcus from the orbital margin, whereas the configuration in M 3055 is colobine-like (Fig. 8). The position of the subcentral anterior sulcus in the right hemispheres of MP 36 and M 3055 is similar to that described for Colobus (SOM Fig. S5), but also to fossil papionins (Fig. 7). In all three specimens investigated, the inferior end of the central sulcus is curved, as in contemporaneous fossil papionin specimens. The configuration of the central sulcus in MP 36 differs from the two other specimens, having a very short cleft connected inferiorly, which could potentially be identified as the sulcus subcentralis posterior, contributing to an overall curved aspect. This sulcal arrangement nears the one detected in T. o. darti in our study.

Discussion

Endocranial volumes

To the best of our knowledge, this current study reports and compares for the first time the ECVs of Plio-Pleistocene South African cercopithecoid taxa, with the exception of extinct Theropithecus, for which ECVs were previously estimated by [START_REF] Martin | Allometric aspects of skull morphology in Theropithecus[END_REF] and [START_REF] Elton | Comparative context of Plio-Pleistocene hominin brain evolution[END_REF]. Our estimates of T. oswaldi ECVs (134-170 cm 3 , including both T. o. oswaldi and T. o. darti) fit within the fairly wide range estimated by Martin (1993; 154-200 cm 3 ) from three T. oswaldi crania from East Africa (Peninj DAT 600/82, a T. oswaldi female, Kanjera BM 32102, a T. oswaldi male, and Kanjera BM 14936, a T. oswaldi female). In contrast, ECVs of T. o. oswaldi (168 cm 3 for SK 561) and T. o. darti (134 cm 3 for MP 222 and 170 cm 3 for M 3073) reported in our study are higher than the [START_REF] Elton | Comparative context of Plio-Pleistocene hominin brain evolution[END_REF] estimates (150 cm 3 for T. o. oswaldi SK 561, 122 cm 3 for T. o. darti MP 222, and 143 cm 3 for M 3073; based on regression equations assessed specifically on Theropithecus). The differences between our and previous studies might be explained by the methods used performed, as we estimate ECVs directly by virtually filling the neurocranium and extracting the endocranial volume rather than packing the braincase with seeds [START_REF] Martin | Allometric aspects of skull morphology in Theropithecus[END_REF] or using regression equations derived from the relationship between external cranial dimensions and whole cranial capacity in extant Theropithecus and cercopithecoids [START_REF] Elton | Comparative context of Plio-Pleistocene hominin brain evolution[END_REF]. Besides being noninvasive, the assessment of ECVs based on high-resolution imaging techniques and virtual reconstruction of endocasts is important for understanding primate paleoneurology, not only because of the more direct means of ECV estimation but also because ECV can be more reliably delimited through the virtual exploration of internal bony structures. In addition, our techniques allow the inclusion of incomplete skulls (e.g., MP 222).

Our current study is focused primarily on methodological development, and hence presents preliminary results. It will need to be extended considerably in the future by integrating a larger sample of extant and fossil cercopithecoids (e.g., a total of 339 and 22 extant and fossil cercopithecoid specimens respectively were sampled in [START_REF] Elton | Comparative context of Plio-Pleistocene hominin brain evolution[END_REF]) and considering and testing crucial variables such as sexual dimorphism and allometry. This notwithstanding, in our study, extant Papio has the largest ECVs relative to body size among both extant and extinct cercopithecoid taxa considered, as is also true for brain weight [START_REF] Martin | Allometric aspects of skull morphology in Theropithecus[END_REF]. Macaca specimens (particularly Macaca mulatta) had some of the lowest ECV values for cercopithecoids of 'medium' body mass. A similar finding has previously been reported for Macaca sylvanus [START_REF] Isler | Endocranial volumes of primate species: scaling analyses using a comprehensive and reliable data set[END_REF] but, as in the present study, interpretation was hindered by the small sample. The ECVs computed in our study also conform to previous work showing that extant colobines have smaller brains than other cercopithecoids [START_REF] Martin | Allometric aspects of skull morphology in Theropithecus[END_REF][START_REF] Isler | Endocranial volumes of primate species: scaling analyses using a comprehensive and reliable data set[END_REF]. One of the most interesting results in our study concerned ECV in the fossil colobine C. williamsi, which grouped with the fossil cercopithecine specimens, and at the upper end of the extant cercopithecoid range. At ~20 kg [START_REF] Delson | Body mass in Cercopithecidae (Primates, Mammalia): estimation and scaling in extinct and extant taxa[END_REF], C. williamsi was much larger than extant African colobines, so it is difficult to make direct comparisons with its closest modern relatives without a full allometric analysis. Nonetheless, smaller brains (as seen in extant African colobines) may be related to folivory [START_REF] Martin | Allometric aspects of skull morphology in Theropithecus[END_REF], so the fact that C. williamsi, probably a terrestrial forager [START_REF] Codron | Utilization of savanna-based resources by baboons during the Plio-Pleistocene[END_REF], groups with the other large Plio-Pleistocene cercopithecoids lends support to arguments that it was adaptively different to modern African colobines. It would be informative to investigate the ECVs of terrestrial Plio-Pleistocene East African Cercopithecoides taxa estimated to be smaller (C. alemayehui, C. kerioensis, C. meaveae) or bigger (C. kimeui) than C. williamsi [START_REF] Jablonski | Cercopithecoidea[END_REF].

Taxonomic and evolutionary implications of endocranial organization

In general, the sulcal patterns we observed in the present study conformed to those previously described for cercopithecines [START_REF] Connolly | External Morphology of the Primate Brain[END_REF][START_REF] Falk | Brain evolution in Old World Monkeys[END_REF]. In Parapapio, the organization of the parietal sulci, and especially the position of the central and intraparietal sulci, is consistent across individuals. The taxonomically undetermined specimen STS 538 shares features with the specimens identified as Parapapio, consistent with previous tentative assignment based on external cranial morphology [START_REF] Heaton | Taxonomy of the Sterkfontein fossil Cercopithecinae: the Papionini of Members 2 and 4 (Gauteng, South Africa)[END_REF]. The distinction between the gross endocranial morphology of cercopithecoid specimens from Makapansgat Member 4, on the one hand, from the slightly younger Taung and Sterkfontein Member 4 assemblages, on the other hand, needs to be explained by further investigations of the fossil record, testing potential temporal sensitivity of endocranial organization [START_REF] Delson | Cercopithecoid biochronology of the African Plio-Pleistocene: correlation among eastern and southern hominid-bearing localities[END_REF][START_REF] Delson | Chronology of South African australopiths site units[END_REF][START_REF] Mckee | Taxonomic and evolutionary affinities of Papio izodi fossils from Taung and Sterkfontein[END_REF][START_REF] Mckee | Faunal assemblage seriation of Southern African Pliocene and Pleistocene fossil deposits[END_REF].

Our visualizations also highlighted interesting variation that adds to our knowledge of sulcal pattern in Old World monkeys. In the T. o. darti specimen M 3073, the subcentral posterior sulcus in the left hemisphere, linked with the central sulcus, appears similar to those described for T. o. oswaldi L 238-29 from Omo [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF]. Comparing T. o. darti M 3073 with the other Makapansgat T. o. darti, MP 222 (neither of which were available for study by [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF]), as well as the forms from Hadar described by [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF], it is evident that considerable variation exists within the subspecies. This variation might overlap with that observed in previous work [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF] on eastern African T. o. oswaldi. [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF] suggested that the strongly curved ('hook-like') inferior end of the central sulcus resulted from the merging of the central and subcentral posterior sulci and is derived for T. o. oswaldi compared to T. o. darti. We suggest that T. o. darti from Makapansgat may show a transitional gyrification pattern, which could stretch the appearance of the derived condition back to c. 3 Ma [START_REF] Brock | Preliminary paleomagnetic results from Makapansgat and Swartkrans[END_REF][START_REF] Mcfadden | Palaeomagnetism and the age of the Makapansgat hominid site[END_REF][START_REF] Delson | Cercopithecoid biochronology of the African Plio-Pleistocene: correlation among eastern and southern hominid-bearing localities[END_REF], rather than to 1.9-2.0 Ma as initially proposed by [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF]. Moreover, the 'hook-like' configuration is not found among extant geladas, where the subcentral posterior sulcus remains perceptible. Accordingly, based on this potential autapomorphic feature, the divergence of the extant Theropithecus gelada lineage from the T. oswaldi lineage could predate the chronological period represented by Makapansgat Member 4, as proposed by [START_REF] Jolly | The classification and natural history of Theropithecus (Simopithecus) (Andrews, 1916), baboons of the African Plio-Pleistocene[END_REF]. However, given that the mechanism for the formation of folding in the primate cortex

is not yet fully understood (even if probably related to biomechanical constraints [START_REF] Van Essen | A tension-based theory of morphogenesis and compact wiring in the central nervous system[END_REF][START_REF] Hilgetag | Developmental mechanics of the primate cerebral cortex[END_REF][START_REF] Toro | A morphogenetic model for the development of cortical convolutions[END_REF][START_REF] Toro | On the possible shapes of the brain[END_REF][START_REF] Bayly | Mechanical forces in cerebral cortical folding: a review of measurements and models[END_REF][START_REF] Tallinen | On the growth and form of cortical convolutions[END_REF]), phylogenetic interpretations of sulcal pattern should be considered tentative.

It is acknowledged that genetic factors are known to influence the developmental pattern and mechanical forces acting on cortical sheet expansion and folding [START_REF] Rakic | A small step for the cell, a giant leap for mankind: a hypothesis of neocortical expansion during evolution[END_REF][START_REF] Bae | Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning[END_REF]. It is thus possible that allometric factors influence gyral and sulcal pattern in Theropithecus. This has implications for the way in which we interpret the evolutionary relevance of sulcal pattern, particularly since a correlation has been reported between increase in brain size and increase in gyrencephaly in mammal orders [START_REF] Pillay | Order-specific quantitative patterns of cortical gyrification[END_REF].

Moreover, because of the mechanisms of gyrogenesis [START_REF] Welker | Why does cerebral cortex fissure and fold? A review of determinants of gyri and sulci[END_REF], variation in developmental process may also contribute to sulcal patterns in mature individuals.

Accordingly, cerebral ontogenetic changes may also play a role in the variation seen in the genus Theropithecus, especially given the developmental differences described for extant geladas compared to other papionins [START_REF] Swindler | The development and microstructure of the dentition of Theropithecus[END_REF].

Another intriguing finding was the variation we observed in C. williamsi endocranial organization. All three specimens included in this study that are assigned to C. williamsi shared features with Colobus, as revealed by the statistical classification of the well-preserved specimen M 3055 among extant colobines, although the morphoarchitecture of C. williamsi endocasts does not mirror the pattern seen in extant colobines: specific colobine-like structures such as the paroccipital sulcus were not identified in our Cercopithecoides sample, even if as pointed out by Tobias (1987: 746) "valuable information may flow from the presence of a sulcus or of a convolutional bulge on an endocast, whereas the absence of an impression may be of dubious morphological significance". One specimen, MP 36, also showed a configuration of the inferior part of the central sulcus very similar to the T. o. darti specimen M 3073. MP 36 is mainly represented by the neurocranium and meager tooth fragments, and has variously been attributed to Simopithecus darti (by R. Broom and J.S.

Jensen; see [START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF]), Pp. broomi [START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF][START_REF] Eisenhart | The fossil cercopithecoids of Makapansgat and Sterkfontein[END_REF], and, most recently, C. williamsi [START_REF] Fourie | Biogeochemical and craniometric investigation of dietary ecology, niche separation, and taxonomy of Plio-Pleistocene cercopithecoids from the Makapansgat Limeworks[END_REF]. Given the sulcal similarities we observed between MP 36 and M 3073, it is possible that MP 36 is actually T. o. darti, although more research to illuminate species-specific variation in cercopithecoids would be desirable. Additional research would also be useful to help understand the evolutionary history of sulcal pattern in colobines. The extant colobine sulcal pattern as described by [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF] in African and Asian taxa, characterized notably by the presence of an arched intraparietal sulcus and the divergence of the principal sulcus from the orbital border, among other aspects, is present in Mesopithecus pentelici [START_REF] Radinsky | The fossil evidence of anthropoid brain evolution[END_REF], a Eurasian Pliocene colobine. Recent work has suggested that Cercopithecoides williamsi is a definitive member of the African colobine clade [START_REF] Frost | The hand of Cercopithecoides williamsi (Mammalia, Primates): earliest evidence for thumb reduction among colobine monkeys[END_REF], implying that modern African colobines are more distantly related to Mesopithecus than they are to C. williamsi. Thus, similarities in the sulcal patterns of Mesopithecus and extant African colobines must either have arisen convergently, or Cercopithecoides shows sulcal morphology that is derived relative to other colobines. Our knowledge of this would also be enhanced further by including Cercopithecoides haasgati [START_REF] Mckee | New species of Cercopithecoides from Haasgat, North West Province, South Africa[END_REF], and indeed other large African colobines, into analyses.

It must also be considered that sulcal pattern may be linked to function, and it is possible that functional convergence may explain some of the similarities between C. williamsi and papionins. Based on sulcal pattern, [START_REF] Falk | Sulcal patterns of fossil Theropithecus baboons: phylogenetic and functional implications[END_REF] hypothesized that T. oswaldi had a relatively expanded cortical somatic sensory and motor face representation compared to the geladas, potentially due to the specialization for mastication of abrasive food. However, making interpretations of function from sulcal pattern is problematic: some inconsistencies in correspondence between sulcal and cytoarchitectural areas have been identified, meaning that the cerebral areas delimitated by sulci on the external cortical surface do not systematically coincide with functional areas [START_REF] Amunts | Broca's region revisited: cytoarchitecture and intersubject variability[END_REF]but see Fischl et al., 2008). Hence, very little can be reasonably inferred about function from our data.

Conclusions

Despite the relative abundance of nearly complete cercopithecoid neurocrania in the paleontological assemblages, endocranial condition has not yet been fully detailed in the South African Plio-Pleistocene records, mainly because of the difficulties related to the extraction of fossil endocasts. Through non-destructive X-ray radiation based high-resolution 3D tomography imaging techniques, we successfully reconstructed virtual endocrania from a representative sample of fossil cercopithecoids and reported ECVs for the first time, as well as morphological and structural variations. In particular, we contributed more information regarding the variation in sulcal pattern in Theropithecus. As previously suggested in the East African context, the Theropithecus fossil lineages present specific derived sulcal patterns, suggested to be useful for taxonomic identification, especially of isolated neurocrania. The identification of this landmark feature in the Makapansgat record supports the possibility of the divergence between the Theropithecus fossil lineages and Theropithecus gelada prior to 3 Ma. Our investigation of C. williamsi endocasts reveals an ECV and sulcal pattern similar to the papionin condition. Given that Cercopithecoides, a committed terrestrialist, differed substantially from the arboreal existence observed in its living counterparts, similarities with papionins in terms of cortical organization might potentially support the hypothesis of an extinct colobine taxon that was adaptively different to modern African colobines.

Besides traditional analyses of the outer cranial morphology, high resolution virtual imaging of fossil primate endocasts allowing the automatic detection of neocortical relief coupled with deformation-based models and morphometrical analyses have the potential to add a significant amount of taxonomic and phylogenetic information. Further research in virtual endocranial paleoprimatology to be developed at a continental scale, including fossil specimens from the rich East African cercopithecoid-bearing sites and notably representatives of the Theropithecus genus [START_REF] Jablonski | Theropithecus: The Rise and Fall of a Primate Genus[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 | Fossil Cercopithecidae from the Middle Pleistocene Dawaitoli Formation, Middle Awash Valley, Afar Region, Ethiopia[END_REF][START_REF] Frost | Fossil Cercopithecidae from the Hadar Formation and surrounding areas of the Afar Depression, Ethiopia[END_REF][START_REF] Frost | Middle Pleistocene fossil Cercopithecidae from Asbole, Afar Region, Ethiopia[END_REF][START_REF] Jablonski | Koobi Fora Research Project[END_REF][START_REF] Gilbert | Partial skeleton of Theropithecus brumpti (Primates, Cercopithecidae) from the Chemeron Formation of the Tugen Hills, 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], would better clarify the polarity, intensity, and timing of the evolutionary changes among cercopithecoid lineages. For each view, the hidden side of the endocranial surface was virtually removed. For each view, the hidden side of the endocranial surface was virtually removed. [START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF][START_REF] Freedman | South African fossil Cercopithecoidea: a re-assessment including a description of new material from Makapansgat, Sterkfontein and Taung[END_REF][START_REF] Brain | The Hunters of the Hunted? An introduction to African Cave Taphonomy[END_REF][START_REF] Mckee | Taxonomic and evolutionary affinities of Papio izodi fossils from Taung and Sterkfontein[END_REF][START_REF] Jablonski | Fossil Old World monkeys: the late Neogene radiation[END_REF][START_REF] Heaton | Taxonomy of the Sterkfontein fossil Cercopithecinae: the Papionini of Members 2 and 4 (Gauteng, South Africa)[END_REF] Ditsong Wits Necsa Pal. Centre Taung [START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF][START_REF] Freedman | New cercopithecoid fossils, including a new species, from Taung, Cape Province, South Africa[END_REF]Jablonski and Frost, 2010 Wits Pal. Centre 76.9

Theropithecus oswaldi oswaldi SK 561 Swartkrans (Member 1) [START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF]Freedman and Brain, 1977;[START_REF] Brain | The Hunters of the Hunted? An introduction to African Cave Taphonomy[END_REF] Mollett, 1947;[START_REF] Freedman | The fossil Cercopithecoidea of South Africa[END_REF][START_REF] Maier | New fossil Cercopithecoidea from the lower Pleistocene cave deposits of the Makapansgat Limeworks, South Africa[END_REF][START_REF] Eisenhart | The fossil cercopithecoids of Makapansgat and Sterkfontein[END_REF][START_REF] Jablonski | Fossil Old World monkeys: the late Neogene radiation[END_REF][START_REF] Heaton | Taxonomy of the Sterkfontein fossil Cercopithecinae: the Papionini of Members 2 and 4 (Gauteng, South Africa)[END_REF][START_REF] Fourie | Biogeochemical and craniometric investigation of dietary ecology, niche separation, and taxonomy of Plio-Pleistocene cercopithecoids from the Makapansgat Limeworks[END_REF] [START_REF] Brain | The Hunters of the Hunted? An introduction to African Cave Taphonomy[END_REF][START_REF] Heaton | Taxonomy of the Sterkfontein fossil Cercopithecinae: the Papionini of Members 2 and 4 (Gauteng, South Africa)[END_REF]

Wits

  and the color maps illustrating the changes from the GMS to each TMS of extant and fossil individuals are depicted in Figures 4-5 and SOM Figure S3. On the whole, three main groups are evident based on the distribution of the living specimens in shape space, corresponding to the three cercopithecoid tribes (Cercopithecini, Papionini and Colobini) represented in our study (Fig. 3, see also comments SOM Results). Along the second component bgPC2, the extant representatives of the cercopithecin genera Cercopithecus, Chlorocebus, and Erythrocebus are grouped together in the negative values and are clearly separated from the rest of the sample. The extant papionins are grouped in the positive values of both axes. The colobines Colobus and Piliocolobus are found in the positive space of bgPC2 and negative values of bgPC1. The fossil papionins plot between the colobines and Mandrillus / Papio, close to Macaca and the mangabeys (Fig. 3). The fossil specimens attributed to Parapapio and Papio are roughly characterized by an elongation and a relative elevation of the frontal pole compared to the GMS (Fig. 4). The occipital lobes are shifted inferiorly and their volumes are significantly reduced in comparison to the GMS. The endocranial regions affected by taphonomic processes and virtually corrected in STS 565, MP 221, and MP 224 do not contribute to excessive local deformations. The large vector identified in the inferior part of the TP 7 endocast could be related to the manual segmentation performed for the extraction of the surface. The condition displayed by the taxonomically undetermined specimen STS 538 is close to the Parapapio and Papio specimens, notably by the elevation of the superior surface and the lower position of the occipital lobes.

  disorders affecting the surface in contact with the basicranium. The two T. o. darti specimens, M 3073 and MP 222, group more closely with fossil Parapapio and Papio and with the Macaca and Lophocebus conditions than to extant Theropithecus in shape space. The color maps point out a significant contraction of the parietal superior surface for MP 222, corresponding to the reconstructed region and responsible for the relative elevation of the occipital and frontal lobes. The M 3073 specimen is close to the GMS and differs from the reference mainly by a bi-temporal enlargement. The deformation pattern displayed by the fossil specimen M 3055, attributed to C.

Figures 7 -

 7 Figures 7-8 for Papio, Parapapio, Theropithecus, and Cercopithecoides. Globally, Parapapio

Figure legends Figure 1 .

 legends1 Figure legends

Figure 2 .

 2 Figure 2. Log endocranial volume (ECV) against log body mass for Plio-Pleistocene and

Figure 3 .

 3 Figure 3. Between-group principal component analysis (bgPCA) of the deformation-based

Figure 4 .

 4 Figure 4. Comparative maps of morphological deformations from the global mean shape

Figure 5 .

 5 Figure 5. Comparative maps of morphological deformations from the global mean shape

Figure 6 .

 6 Figure 6. Hierarchical classification based on the distances computed from the endocast

Figure 7 .

 7 Figure 7. Virtual reconstructions of Parapapio endocasts with sulcal impressions in superior

Figure 8 .

 8 Figure 8. Virtual reconstructions of Theropithecus and Cercopithecoides endocasts along

  mentioned, the specimens from Sterkfontein and Swartkrans derive from Member 4 and Member 1, respectively, and those from Makapansgat are from Member 4

  . b Abbreviations for storage locations: Ditsong = Ditsong National Museum of Natural History, Pretoria; Wits = University of the Witwatersrand, Johannesburg; MNHN = Muséum national d'Histoire naturelle, Paris; MRAC = Musée royal de l'Afrique centrale, Tervuren; AMNH = American Museum of Natural History, New York; MHNT = Museum d'Histoire naturelle de Toulouse c Nesca = South African Nuclear Energy Corporation, Pretoria (Hoffman and De Beer, 2012); Pal. Centre = Palaeosciences Centre, University of the Witwatersrand, Johannesburg; AST-RX = Accès Scientifique à la Tomographie à Rayons-X, MNHN, Paris; FERMaT = Fédération Fluides Energie Réacteurs Matériaux et Transferts, Toulouse; MIF = Microscopy and Imaging Facility, AMNH, New York (data provided by Pr Eric Delson and the AMNH Department of Mammalogy, some specimens were downloaded from www.morphosource.org, Duke University), MEDES = Faculté de Chirurgie Dentaire de Toulouse.

Figure_1

  Figure_1Click here to download high resolution image

Table 1

 1 List of the Plio-Pleistocene and extant cercopithecoid specimens/samples included in the study.

		Parapapio broomi				Parapapio jonesi	|Fossil taxa
	STS 564	224 d , MP			STS 565	sample	Specimen/
	(Member 4)	Makapansgat	(Member 4)	Sterkfontein	(Member 4)	Sterkfontein	provenance a	Site/
						1981; Jablonski, 2002	Eisenhart, 1974; Brain,	Freedman, 1957;	Source
							Ditsong	at b	Stored
							Necsa	µCT equipment c
							71.9	voxel size (µm)	acquisition	µCT

Acknowledgments

We are indebted to S. Potze (Pretoria), B. Zipfel (Johannesburg), J. Cuisin (Paris), G. Fleury (Toulouse), and W. Wendelen (Tervuren) for having granted access to fossil and comparative material under their care. We also thank K. Carlson and T. Jashashvili (Johannesburg), G. Clément and M. Garcia-Sanz (Paris), L. Bam (Pretoria), and D. Maret and E. Coudrais (Toulouse) for (micro-X-ray) tomographic and CBCT acquisitions, and E. Delson (New York) for providing CT scans. For scientific contribution and/or for discussion and comments to the results presented in this study, we are especially grateful to E. Delson (New York), D. Ginibriere (Toulouse), J. Heaton (Birmingham), N. Jablonski (University Park), O. Kullmer (Frankfurt), R. Macchiarelli (Poitiers & Paris), M. Nakatsukasa (Kyoto), L. Pan (Toulouse), and C. Zanolli (Toulouse). The present version greatly benefited from the comments provided by the Editor, the Associate Editor, and three anonymous reviewers. The French research federation FERMaT (FR3089), the National Research Foundation (NRF), and Department of Science and Technology (DST) of South Africa are acknowledged for providing micro-X-ray tomography laboratory facilities. This work was granted access to the HPC resources of CALMIP supercomputing center under the allocation 2015-[P1440] attributed to the AMIS laboratory. Research supported by the Center of Research and Higher Education (PRES) of Toulouse, the Midi-Pyrénées Region, and the French Ministry of Foreign Affairs.