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The Late Cretaceous is marked by numerous environmental disturbances and a mass extinction at the Cretaceous-Paleogene (K/Pg) boundary, which has been widely explored for marine and continental faunas, but whose impacts on freshwater environments remain poorly studied to date. Amphibians and squamates (lizards and snakes), generally abundant in freshwater ecosystems, are relatively sensitive to environmental changes. Nevertheless, the consequences and modalities of Late Cretaceous environmental changes on their diversity are still poorly understood, owing to the fragmentary nature of their fossil record, particularly in France, where it is limited to a few localities that have yielded isolated, incomplete, and poorly identifiable elements. New material from previously unstudied and historical sites, stratigraphically distributed throughout the Late Cretaceous across several continental sedimentary basins, has enabled the discovery of numerous amphibian and squamate taxa. Among these, several taxa represent the oldest occurrences of their clade in Europe or even worldwide, while others possess novel characters justifying the description of new species. The palaeobiogeographic and palaeoecological implications of these discoveries are also discussed. This thesis provides an in-depth study of this material and a fresh perspective on amphibian and squamate diversity during the Cretaceous, notably through the use of 3D imaging, which not only makes it possible to identify morphological characters previously obscured by sediment, but also to observe the internal structures of the fossils studied. This work provides valuable information on the distribution and evolutionary history of European amphibians and squamates, particularly for the Campanian-Maastrichtian, contributing to a better understanding of the faunal and diversity changes occurring in freshwater ecosystems around the K/Pg boundary.

  • Completed on: December 12 2024
  • PhD Student: Tomas Getachew BEDANE
  • PhD supervisors: Jean-Renaud BOISSERIE (directeur HDR), Mackaye HASSANE TAÏSSO (Senior Lecturer, Department of Paleontology, University of N’Djamena, Tchad)

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This dissertation investigates the paleoecology and evolutionary dynamics of Neogene Elephantids from East Africa’s Awash and Turkana Basins (Ethiopia and Kenya) and Central Africa (Chad), focusing on their dietary strategies and ecological adaptability. By integrating multiple analytical methods dental mesowear, dental microwear, dental calculus analysis, and stable isotope analysis the study reconstructs the feeding behaviors and habitat use of both fossil and modern Elephantid species across different regions and time periods. The findings reveal that Neogene Elephantids exhibited mixed feeding strategies, enabling them to adapt to diverse ecological niches that included a combination of browsing on trees and shrubs (C3 plants) and grazing on grasses (C4 plants). Dental mesowear analysis suggests long-term dietary flexibility, while microwear patterns provide insights into short-term feeding behaviors, showing variability linked to regional vegetation. Additionally, analysis of dental calculus revealed traces of both C3 and C4 vegetation, further corroborating their dietary diversity. Stable isotope analysis highlights a dietary shift over time, with fossil Elephantids predominantly grazing on C4 grasses in open habitats, while modern species increasingly consumed C3 browse in wooded environments. These findings underscore the ecological flexibility of Elephantids, which allowed them to adapt to changing landscapes and climatic conditions during the Neogene and Quaternary. By demonstrating how dietary plasticity influenced their survival and evolutionary trajectory, this research provides valuable insights into the broader patterns of mammalian evolution in response to environmental change.

  • Completed on: December 21 2023
  • Doctorante : Alicia BLASI-TOCCACCELI
  • PhD supervisors: Michelle DRAPEAU (Université de Montréal), Evie VEREECKE (KU Leuven), Stephanie MELILLO (Mercyhurst University), Tea JASHASHVILI (University of Southern California), Gilles BERILLON (HNHP, Paris), Mathieu DOMALAIN (Institut Pprime, université de Poitiers), Guillaume DAVER, Jean-Renaud BOISSERIE (PALEVOPRIM)

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Dexterity-related behaviors play an important role in the behavioral repertoire of hominins, particularly within the genus Homo. However, studies of hominin postcranial anatomy, with the exception of the hand, have mainly focused on postural-locomotor capacities rather than on stone tool-making and use or on high-speed throwing activities. In particular, the shoulders of Australopithecus and Paranthropus have been described as primitive compared to Homo sapiens, reflecting postural-locomotor activities such as suspension. In contrast, the emergence of the genus Homo, particularly H. erectus, is associated with a more derived shoulder morphology. This derived shoulder is interpreted as having been freed from locomotor constraints, and some authors suggest that it may even have been selected for dexterity-related activities. Yet the relationships between shoulder morphology and stone tool-making have not been studied in depth, making it impossible to address the broader question of the evolutionary selection of morphological traits in hominins. The main objectives of this thesis are therefore i) to reassess and compare shoulder morphology in Homo, Australopithecus, and Paranthropus using an up-to-date 3D fossil database (including new specimens described in the present work), and ii) to reassess the functional role of the main morphological features of the hominin shoulder in light of dexterity-related activities, using evolutionary biomechanics.

  • Completed on: December 12 2023
  • PhD Student: Axelle WALKER
  • PhD supervisors: Debbie GUATELLI-STEINBERG (université d’État de l’Ohio, USA), Ellen SCHULZ-KOMAS  (université de Leipzig, Allemagne), Laura MARTINEZ MARTINEZ (université de Barcelone, Espagne), Cédric GAUCHEREL (INRAE, UMR AMAP, Montpellier), Vincent LAZZARI, Franck GUY, Gildas MERCERON (PALEVOPRIM)

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In paleontology, the study of teeth is essential for identifying species, understanding their evolution, and inferring ecological information such as diet. In mammals, tooth shape results from phylogenetic inheritance, development, and the selective pressure exerted by masticatory constraints linked to diet. Dental adaptations reflect adaptive responses to specific diets. During the Cenozoic, primates underwent major dental changes in response to environmental variation, favoring their expansion and diversification. The divergence between hominoids and cercopithecoids constitutes a key example for understanding dental adaptations and the relationship between molar shape and food comminution. My thesis explores different methodologies to deepen our understanding of dental diversity. In the first part, I focus on the occlusal morphology of teeth, viewed as a set of tools for food processing. I use 3D topographic analysis to identify specific dental features, focusing on aspects related to sharpness (crenulations and lophs). The results indicate that certain features associated with dental sharpness can reveal folivorous and herbivorous diets in catarrhines. However, when focusing on the most curved parts of the tooth, the signal becomes more distinct, making it possible to distinguish different crest shapes. In the second part, I use geometric morphometrics to examine cercopithecoid lophs in detail. I explore the hypothesis that lophs not only guide occlusal movements but also contribute to food fragmentation. I support this analysis with experiments assessing the mechanical efficiency of lophs in cercopithecines, using theoretical models of lophs and a mechanical tester.

  • Completed on: July 11 2023
  • Doctorante : Sophie Gabriele HABINGER
  • PhD supervisors (joint supervision / co-tutelle): Kathryn FITZSIMMONS (Eberhard Karls Universität Tübingen), Stéphane DUCROCQ, Olivier CHAVASSEAU (PALEVOPRIM), Hervé BOCHERENS (Eberhard Karls Universität Tübingen), Brooke Erin CROWLEY (University of Cincinnati), Larisa R. G. DE SANTIS (Vanderbilt University)

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The Cenozoic fossil formations of Southeast Asia document a highly dynamic period in mammalian evolution. Many clades of modern mammals originated from this biogeographic region or experiencing important radiations there including anthropoid primates and pongines. Here, I want to characterize the ecological and environmental contexts in which these developments took place, specifically regarding palaeoseasonality, vegetation structure, diet and niche partitioning. To do so, I focused on two fossil mammal assemblages from the Central Basin of Myanmar representing two key time periods in the evolutionary history of primates.The greenhouse world of the middle Eocene Pondaung Fm. is a window to explore the ecosystem dynamics in the faunal assemblage of a habitat, which sustained a large number of different early anthropoid primates as well as a diverse fauna of herbivorous mammals. Previous studies focused on climate and vegetation of the Pondaung environment. While I also worked on aspects of paleoseasonality and vegetation structure, my focus lay on the structure of microhabitats across the different localities of the Pondaung Fm. and their use by the different taxonomic groups. Based on this work, I could infer ecological flexibility for at least some of the anthropoid primate species, based on their occurrences in different microhabitats. The second focal point of my work on the Pondaung fauna were the anthracotheres and a detailed reconstruction of their paleoecology and the competition dynamics between the five species.With the second mammal assemblage, we want to address open questions surrounding the evolutionary ecology of Ponginae in Southeast Asia. Today, there only is one genus (Pongo), whose geographical distribution is highly restricted to the islands of Borneo and Sumatra. From the Miocene to the Pleistocene however, species diversity and geographic range were much more extensive. The fossil record of pongines spans the area from Turkey to southern China. The late Miocene Irrawaddy Fm. is an example for the habitat of the sister-group of extant orangutans, Khoratpithecus, which is represented here by the species Khoratpithecus ayeyarwadyensis. I characterized the habitat of this fossil pongine by reconstructing its paleoseasonality, vegetation structure and niche partitioning dynamics. Then focused my work on the question if there was ecological continuity in the pongine clade since the Miocene, with a comparison of the different taxa from South and Southeast Asia.For my studies, I used to different analytical approaches to assess paleoecology and diet in these fossil mammal faunas. Here, I present the stable isotope analysis and subsequent niche modelling of the Eocene and Miocene fossil assemblages from Myanmar and the dental microwear texture analysis I used to get a more detailed insight into pongine evolutionary ecology with the comparison of subsistence strategies of Miocene pongines to Pleistocene and extant orangutans. With the different studies of my dissertation project, I could show possibilities to push the boundaries of stable isotope niche modelling by using a different set of isotopes that are representing more general ecological characteristic of a niche rather than just trophic or dietary dimensions. I also successfully explored the application of new approaches with the modelled isotopic niches that previously were only used by stable isotope ecologists working on modern ecosystems to geological time periods. One example is the evaluation of competition potential dynamics in the anthracothere assemblage from the Pondaung Fm. The work on the Selenka orangutans was another way in which I could bridge the gap between palaeontology and ecologists and biologists working on extant primate faunas in providing a data set that opens new research directions in both fields.

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The Plio-Pleistocene period provides records of crucial climatic and ecosystem changes that coincides with key events during the course of human evolution, notably in eastern Africa. In this context, the timing, ecological and behavioral implications of the dietary shift of hominids towards tool assisted consumption of animal tissue is far from being addressed. In the Turkana region, the record dated from 3.6 Ma to 1 Ma from the Shungura Formation, although rich in faunal and artifacts, were never investigated from a zooarchaeological perspective. This thesis examines the taphonomic and paleoenvironmental contexts of the vertebrate assemblages contemporaneous to the human occupation sites in this formation. My objective was to address the subsistence behaviors of early hominids, the ecological context of the Oldowan and of newly discovered Acheulean localities.The first part focuses on presenting the taphonomic assessments made throughout the Shungura sequence. After preliminary taphonomic analysis, identification and description of various mark were documented. The Shungura Formation provides a perfect testing ground for discriminating various Bone Surface Modification (BSM) agents. Classic zooarchaeological methods and geometric morphometrics-based quantitative analyses were combined to deal with strong equifinality between anthropic and non-anthropic BSM. Fossil BSMs were compared with experimental samples including anthropogenic cut marks, trampling marks, as well as crocodilian and carnivoran tooth scores. For the characterization of BSM morphologies, I used an Elliptic Fourier (EF) based approach. In depth analyses of BSMs revealed crocodiles to be active agents in all members of the formation, being particularly abundant in members C and G. Anthropogenic activity has been confirmed in members F, G, and L, based on the presence of cut marks as well as hack marks. While some debate still remains on the effective differentiation of BSMs, especially in contexts where both crocodiles and hominids coexist, the present EF based approach was able to confirm the presence of both cut marks, as well as crocodilian tooth marks, while effectively discriminating between the two. Likewise, I have been able to effectively identify hominid butchery activities in this area as early as 2.3 Ma. The second part of the dissertation presents paleoenvironmental data surrounding the emergence of the Oldowan in the Shungura (at 2.3 Ma) through synthesizing multiple lines of evidence using taphonomy, faunal composition data, as well as 3D dental microwear textural analysis. This part examines the faunal assemblages in relation to the archaeological occurrences in the lower part of Member F. I have applied DMTA to five bovid tribes from two excavation localities immediately predating the Oldowan occurrence. The DMTA results show intra-locality differences within Aepycerotini and Alcelaphini. DMTA analysis identified grazing dietary behavior at L 398, whereas at OMO 33 these taxa show a tendency towards mixed feeding behavior. Bovid tribes from each unit in Member E and F were also analyzed in order to compare the faunal signals change through time, and between localities for spatial analysis within Member F. The overall bovid data at member level indicates that there was a shift towards more arid and open in Member F. The faunal data and DMTA analysis provided additional information on how paleohabitats varied across landscapes at a relatively shorter temporal resolution. At F-0, I have observed both a significant increase in the abundance of Alcelaphini and dietary discrepancies among sympatric taxa. Thus, my results suggest local scale ecological variability in Member F, more prominently than in Member E.

  • Completed on: November 28 2022
  • PhD Student: Margot LOUAIL
  • PhD supervisors: Gildas MERCERON (PALEVOPRIM), Antoine SOURON (co-directeur, Université de Bordeaux) et Xavier MILHET (co-encadrant, Institut Pprime).

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During the Cenozoic, changes in dental morphology are observed in several mammalian clades, such as ruminants, suids and hominins. These modifications are often considered to reflect adaptations to increasingly abrasive diets associated with the progressive aridification and opening of environments. The Late Pliocene and Early Pleistocene constitute a key period in the evolutionary history of hominins. It is notably characterized by an important taxinomic diversity including gracile and robust forms. Different strategies developed during periods of food scarcity would help explain this diversity and the ecological niche partitioning among contemporaneous taxa. They thus shed light on the factors that have favored the selection of robust craniomandibular and dental phenotypes. However, the past ecologies of Plio-Pleistocene hominins remain poorly understood. In order to refine our interpretations of the variations of craniomandibular and dental ecological proxies to understand past ecosystems, an experimental model using an omnivorous bunodont mammal is developed. Hence, this thesis is based on nearly 200 domestic pigs distributed in about thirty different controlled-feeding experiments. Different craniomandibular and dental proxies are studied: micro- and meso-wear, biogeochemistry of enamel and mandibular morphology. This work highlights the potential of these proxies to detect the consumption of small to moderate proportions of food resources with physical and mechanical properties similar to those of foods potentially targeted by early hominins during period of food scarcity (fallback foods): seeds, herbaceous plants, C4 plants, animal matter and underground storage organs. Moreover, some resources seem to leave more traces than others on cranio-dental archives, and seem to generate more constraints on mastication and dental abrasion. The results obtained allow us to propose future developments for a better calibration of these ecological proxies, as well as to test these experimental observations on extant wild taxa. The dental microwear analysis of extant suids, in light of the experimental results, highlights relatively subtle differences in feeding habits. Paleoecological inferences are then proposed for Kolpochoerus from the Shungura Formation (Plio-Pleistocene, Ethiopia) based on their dental microwear. This thesis contributes to a better understanding of the behavior of frequently used ecological proxies following the consumption of different resources, and provides new insights to refine our paleoecological inferences.

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Material of the vertebrist paleontologist, the fossilized skeletal tissues represent an original archive, rich in ecological and environmental information in ancient times. They also record information on the history and living conditions and provide information on the functional adaptations of organisms, essential elements for understanding biological evolution in relation to environmental changes. These aspects are addressed in the thesis, through the exploration and development of different methodological approaches.The skeletal growth marks of freshwater actinopterygians and chelonians from intertropical Africa are considered a marker of paleo-seasonality. The development of this tool involves the construction of a reference database on extant species close to fossil ones and is broken down into two complementary studies. In a first part, I demonstrate from the analysis of the results of an experiment on 3 intertropical species (Polypterus senegalus, Auchenoglanis occidentalis and Pelusios castaneus), that the seasonal growth of these species is mainly controlled by the abundance of food, and sometimes by water temperature. In a second part, I demonstrate that the exploration of bone growth in wild individuals of Lates niloticus is indeed correlated with seasonal cycles. These first results also make it possible to specify the future developments to be carried out to calibrate this seasonality marker. In a third part is presented the sampling carried out for an application in the Shungura Formation (Plio-Pleistocene, Ethiopia) with the first observations.Based on the synthesis of the ecology and physiology of crocodilians, I was able to show that the oxygen isotopic composition of their dental tissues mainly reflects that of the water in which they lived during the formation of the tooth. In a first study, the oxygen isotopic composition of the bulk enamel of fossils from the Shungura Formation is interpreted, and provides information on the evolution of freshwater environments and their local diversity over two million years. In a second study sampling dentin serially, preliminary results show fluctuation consistent with the seasonality of climate for some samples. These first data allow proposing a protocol in order to interpret the recorded signal and to discuss the evaluation of the impact of diagenesis.Finally, the study of the detailed functional anatomy of the external bony structures (morphology, articular facets, muscular insertions, proportions) on the appendicular skeleton allows inferences on the locomotor behaviour and more generally on the paleoecology of Amphicynodon leptorhynchus (Carnivora, Arctoidea) from the Phosphorites of Quercy (Lower Oligocene, France). In a first part, the functional analysis of the hind limb reveals adaptations to climbing and allows to conclude on probable arborealism. In the second part, a paleoartistic restoration by Amphicynodon leptorhynchus is elaborated on the basis of anatomical arguments and in coherence with the environmental context.A perspective of the methodological contributions addressed to scientific questions on evolution in its environmental context is proposed, with a particular focus on questions of seasonality and paleoecological inferences.

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The fossil record from the Plio-Pleistocene documents a drying trend and an opening of the landscapes relative to previous times. A rich monkey fossil record is documented during this period of climatic instability, especially at Shungura. This fossiliferous formation from the Lower Omo Valley (Ethiopia) is also characterized by a precise chronostratigraphic frame that covers particularly well the Plio-Pleistocene transition. Hence, Shungura appears as a benchmark of choice to assess the impact of climate change on fauna and particularly on organisms that relies on mesic and wooded habitats, as is the case for most cercopithecids representatives (colobines and cercopithecines). My dissertation focused on a sound ecological parameter, namely locomotion, and took advantage of uni- and multivariate morphometric methods to test hypotheses regarding locomotor substrate and behaviors on one side, and niche partitioning and ecological dynamic of the cercopithecid from Shungura on the other side. My work first dealt with the colobine fauna, as large-sized colobines (Paracolobus and Rhinocolobus) were identified at Shungura on the basis of craniodental material. However, no description nor morphofunctional analysis of their functional anatomy had yet been undertaken. Following both the description and the uni- and multivariate analysis of 39 postcranial remains (including a partial skeleton), my research permitted to characterize versatile locomotor substrate preferences and an enhance ability to climb in Paracolobus as well as a preference for arboreal substrate and capabilities for suspension in Rhinocolobus. On the basis of these inferences, subsequent ecomorphological analyses highlighted the ecological niche partitioning of these two monkeys. My research further demonstrates the presence in the youngest levels of the formation, of a small-sized arboreal colobines similar to extant African colobines. This information supports the onset of a modern-looking colobine fauna at around 1.5 million years following the demise of the large colobines in addition to document the effect of climate change on the colobine fauna. In a second step, the locomotion of Theropithecus, an abundant cercopithecine genera at Shungura and in others fossiliferous area of eastern Africa, was reassessed on the basis of the descriptive and morphofunctional analysis of a partial hindlimb from the fossil species T. brumpti. My results indicated a preference for terrestrial substrates in T. brumpti and of frequent use of squatting, a posture typical of the genus, but whose identification from osteological correlates were debated up to this day. By taking advantage of the new form-function relationships drawn from the lower limb of T. brumpti, a functional analysis of 190 long bone remains from the entire Shungura sequence was undertaken. This study permitted to i) confirm the phenetic affinity of the forelimb of T. brumpti with the mandrillus one, ii) to provide new hypotheses regarding the ecological niche partitioning of T. oswaldi and T. brumpti and iii) to identify the presence of a modern-looking baboon among the youngest levels of the Shungura formation. Overall, my work questions the lack of kinematic and kinetic data on the locomotion of extant monkeys and demonstrate the necessity to expand comparisons of ecomorphological diversities to monkey faunas from other part of Africa.

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The early Pleistocene is a period of global cooling and climatic oscillations punctuated by glacial and interglacial cycles. This period of climatic instability leads to an alternation of steppe and forest habitats resulting in faunal renewals and dispersals, including Homo dispersal.In paleoenvironmental reconstructions based on faunal assemblages, deer, which are among the most abundant mammals, are traditionally considered forest dwellers. However, this paradigm is far from reflecting the real complexity of deer ecological diversity.Via the textural analysis of 921 representatives of the 5 extant European deer with known ecology, a solid reference database has been setup. It attests of the significative link existing between dental micro-wear and vegetal resources. The analysis of 547 fossils from 15 European localities underlines the ecological diversity among fossil deer. Eucladoceros ctenoides and Metacervoceros rhenanus are plastic in their diet. The analysis of such deer allows the identification of dietary adaptive answers to environmental modifications resulting from climatic oscillations. Being eurytopic, they constitute essential proxies for paleoenvironmental reconstructions. The results challenge the link existing between the occurrence of deer and the presence of forest habitats, as deer are ecologically more diversified.The textural analysis of deer from European human bearing localities aims at characterizing potential habitats favorable toward Homo dispersion in Eurasia.

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Mammalian teeth are a major tool in food cominution and fracture. Conversely, food mechanical properties apply a strong selective pressure on dental morphology. The aim of this manuscript is to investigate whether this adaptive signal can be detected from dental shape in extant and extinct primates.In this context, the 3D dental topography of 31 species of extant primates is analyzed with a combination of traditional and original variables. Furthermore one extinct colobine monkey, Mesopithecus pentelicus from the Late Miocene of Pikermi (Greece) is investigated. The results are interpreted using dietary categories, but also a novel categorization system that evaluates the mechanical scope of food shearing, grinding and cracking.Selected variables show significant differences between dietary categories as well as mechanical scopes across the sample. Moreover, the dental morphology of M. pentelicus is predicted to be intermediate between hard food cracking and tough food shearing taxa.In addition, the new variables show that shearing crests are significantly sharper in tough food shearers, which confirms their suggested role as a dental shearing tool. In contrast, enamel thickness distribution seems more homogenous within durophageous species, which suggests that the whole tooth per se makes the basic cracking tool of primates.

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Humans are characterised by a specific form of bipedal locomotion. Toumaï, holotype specimen of Sahelanthropus tchadensis discovered in Chad, is the oldest known member of the human branch. Dated from 7 million years ago, it is very close to the dichotomy between this branch and the branch of chimpanzees. Therefore, it gives valuable information on the first stages of the evolution of locomotion is this group. The purpose of this work is to reconstruct the locomotor behaviour of Sahelanthropus tchadensis based on the study of the osseous part of its labyrinth, the balance organ.To this aim, the relationships between the locomotion and the bony labyrinth morphology are investigated in extent hominoids. The covariations between the labyrinth and the skull are studied in Homo sapiens in order to determine the influence of cranial integration on labyrinth morphology. Finally, these results are applied to the bony labyrinth of Toumaï, compared to other hominin fossils.Geometric morphometrics discriminates all extant species by the relative orientation, size and shape of each part of the labyrinth. However, the torsion and the relative orientation of the semicircular canals are mainly due to the integration of the labyrinth in the skull (petrous pyramids and face orientations relative to the midline of the basicranium). On the contrary, canal eccentricity and size are linked only to locomotion.In Sahelanthropus tchadensis, the canal size indicates that this species was more agile than great apes. However, it does not have the semicircular canal rotations characterising the genus Homo. The shape of its canals constitutes a unique combination of features: a round posterior canal and a slightly stretched anterior canal, as in humans and australopithecines, but a slightly posterolaterally projected lateral canal, as in gorillas and baboons. This is the sign of a locomotor behaviour associating vertical climbing in trees to both bipedalism and quadrupedalism on the ground.

  • Completed on: November 23 2015
  • PhD Student: Clarisse NÉKOULNANG DJÉTOUNAKO
  • PhD supervisors: Patrick VIGNAUD & Géraldine GARCIA (PALEVOPRIM), Dominique MONCOND’HUY (Laboratoire Forell, Université de Poitiers)

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For the XVth century Italy was a playground of favourite of collectors, private individuals among whom some very early placed their collections at the disposal of the public. The curious collect objects for the most part of the cases for reasons for being able to, of politics or still religious option, but not with the aim of preserving them. However the development of networks of sociability and business in the XVIth century made cabinets of curiosity an European reality. When the collectors die, certain collections are sold and of other one transformed into museum from the XVIIth century, others are also, in the XVIIIth and in the XIXth century, at the origin of collections kept at present in high schools and universities. The history of the European collections, including with regard to the most recent evolution of museums, allows to think about what can and have to be collections today, and as regards their preservation and the conditions of their study, and as for their opening to the public. Yet further to major discoveries in paleontology in Africa, and with the aim of managing and valuing these collections, numerou national museums settle in capitals and museum representation change to become real museums oriented developments of scientific research. It is also through the paleontological discoveries in Africa that the whole world and the Africans became aware themselves of the diversity and the immense natural and patrimonial wealth of this continent. The paleontological collections of the Chad present a very important scientific interest, which results from their impact on the knowledge of the '' Origin and the History of the Human Family ''. On more than 20 000 fossil specimens brought to light by the MPFT, 18343 are inventoried and digitized, including 316 types and figured, a database was built with these guys and figured in Access is posted on the CNAR Site and catalogs on these type specimens were also developed and printed in this work. These collections constitute one of the richest paleontological collections of Central Africa today, in particular for the period of Mio-Pliocène (from 7,3 to 3 My). Also generates an undeniable socio- cultural issue. A study is conducted and trails are proposed to ensure not only a true conservation policy but also of valuation, including the general public. Our thesis intends to contribute on second thought on the future of the African, in particular Chadian collections.

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The Khok Sung sand pit, Nakhon Ratchasima province, has yielded the richest Pleistocene vertebrate fauna of Thailand, where more than a thousand fossil mammals and reptiles (skulls, isolated teeth, and postcranial remains) were recovered. The mammalian fauna, which is described in details hereby, consists of at least 18 identified species (12 genera), including a primate, proboscideans, rhinoceroses, suids, bovids, cervids, and carnivores, which are characterized by mostly extant elements associated to some completely and locally extinct taxa. The age of the Khok Sung fauna is tentatively attributed to the late Middle Pleistocene as either 188 or 213 ka, based on the paleomagnetic data and on the faunal comparisons. The Khok Sung mammal assemblage yields the Stegodon-Ailuropoda faunal association, most similar in composition to that of Thum Wiman Nakin, supporting the hypothesis that northeastern Thailand was a biogeographic gateway of the Sino-Malayan migration route from South China to Java. An analysis of stable carbon isotopes extracted from the tooth enamel of fossil ungulates reveals evidence of niche partitioning among megaherbivores and within cervids. The enamel carbonate d13C values also suggest a considerable amount of C4 plants in the dietary use of ruminants, indicating that grasslands had significantly expanded in Thailand at that time during which anthropic impacts on the ecosystems were absent. The stable oxygen isotope results, obtained from the serial sampling of large mammal enamel, combined with the cenogram analysis reflect significant seasonal variation in precipitations and temperature for Khok Sung, associated to a relatively humid climate.

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Equids, that have a wide geographic distribution and that are an emblematic model of macroevolution, are well documented. Their taxonomy is however unclear, leading to a rampant synonymy often due to a lack of information on the diagnostic validity of characters. African hipparions and Equus, represented mainly by isolated dental material, remain little known compared to North American and Eurasian taxa displaying often more complete specimens. In order to assess the range of variation of dental characters (ontogenetic variation, intra- and interspecific variation, and variation between premolars and molars), a geometric morphometrics analysis combined with 3D imaging and/or biometric measurements is tested for the first time on extant species of Equus. Results are then used to determine or revise the fossil material from hominid-bearing sites of Chad (7 Ma, 5.4 Ma, 4 Ma, 3.6 Ma) and Ethiopia (Shungura Formation, continuous and dated from 3.6 Ma to 1.05 Ma, and that documents the first occurrence of Equus in Africa at 2.27 Ma). A phylogenetic analysis based on a majority of dental characters is then tested and allows discussing the phylogenetic relationships and paleobiogeography of these taxa. A morpho-functional study, which will later be coupled with other paleoecological analyzes, uses equids (generally considered as markers of open areas but that may display diversified diets) as a proxy for paleoenvironments. The study of equids appears therefore important in a chronological framework including significant faunal and environmental changes associated with the emergence of hominids.

  • Completed on: March 25 2015
  • PhD Student: Gisèle MACHADO
  • PhD supervisors: Olga OTERO (PALEVOPRIM), Paulo BRITO (UERJ, Brazil)

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The Ionoscopiformes are an order of fossil actinopterygian fishes with broad temporal and geographic distributions, known from the Middle Triassic to the Late Cretaceous, in Europe, Africa, Asia, and North and South America. The Ionoscopiformes comprise two families, Ophiopsidae and Ionoscopidae, represented by various species, some of which remain poorly known anatomically. Although the Ionoscopiformes are considered a monophyletic group, Ophiopsidae and Ionoscopidae species differ in several characters, including scale type and the ornamentation pattern of the dermal bones. The Ionoscopiformes are placed within the clade Halecomorphi, which comprises three orders (Amiiformes, Parasemionotiformes, and Ionoscopiformes) and several incertae sedis species (e.g., Heterolepidotus, Osteorachis, and Neorhombolepis). The Halecomorphi are considered more closely related to the Ginglymodi than to the Teleostei, and together with the latter they form the clade Holostei. Some of the incertae sedis halecomorph species have previously been associated with the Ionoscopiformes, particularly with the family Ophiopsidae. Several questions regarding the composition of the Ophiopsidae and the position of associated taxa have recently been raised in the literature, such as the placement of the genera Placidichthys, Heterolepidotus, and Furo. The genus Heterolepidotus has been suggested to belong within the family Ophiopsidae, including a basal position within that family, but also as a member of the family Caturidae.
Placidichthys has recently been placed within the Macrosemiiformes, and Furo muensteri within the family Ophiopsidae. Given the clear need to improve our knowledge of Ionoscopiformes species and associated incertae sedis taxa, the present work provides an anatomical review of these taxa along with hypotheses regarding their phylogenetic position within the Neopterygii. On this basis, several taxonomic proposals are put forward. The genera Ionoscopus, Ophiopsis, and Heterolepidotus are redefined, the definitions of the nominal species are revised, and their diagnoses emended. Four species of the genus Ionoscopus are considered valid (I. pietraroiae, I. desori, I. cyprinoides, and I. elongatus), along with six species of Ophiopsis (O. procera, O. breviceps, O. dorsalis, O. lepersonnei, O. montsechensis, and O. lepturus), and only two species of Heterolepidotus (H. rhombifer and H. serrulatus). Cases of synonymy, reversion, nomen nudum, and nomen dubium are also identified. The retained phylogenetic hypothesis does not recover the Ionoscopiformes as a monophyletic taxon.
Nevertheless, the families Ionoscopidae and Ophiopsidae are recovered within the Halecomorphi; a close relationship is also found between the Ionoscopidae and the Amiiformes, while the Ophiopsidae are found to be more closely related to Furo and Heterolepidotus. The internal relationships within the Ionoscopidae and the Ophiopsidae remain unresolved, but Placidichthys is recovered within the Ophiopsidae. The non-monophyly of the Ionoscopiformes and the uncertainties surrounding the position of species close to the Ophiopsidae highlight the need to revise other halecomorph taxa, such as the Caturidae, as well as the need to identify new characters, such as histological ones, in order to improve the resolution and robustness of hypotheses regarding the phylogenetic relationships of these clades.

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North-western Africa, or the Maghreb, occupies a special geographic position, being an integral part of the African continent, but also consisting of an integrated northern Mediterranean area and of a semi-desert or desertic southern area. In the first part, paleomagnetic and biostratigraphic studies based on rodent faunas were carried on continental deposits of two Algerian basins (Tafna and El Eulma). The magnetostratigraphic study realized in this work allowed to estimate the age of various fossiliferous deposits, and to correlate them with various other Neogene basins of North Africa.In the second part, new paleontological prospections in the Aït Kandoula basin (Morocco) led to the discovery of three fossiliferous deposits dated back to late Miocene. These deposits delivered a rich micromammalian fauna associated with large mammal remains. The systematic study of small mammals and especially rodents of deposits from both AF12-1 and AF12-2 allowed identifying taxa which have affinities with those of south-western Europe. These two new localities provide new information on the exchanges of faunas between Africa and Europe. The genus Stephanomys is reported here for the first time in Morocco. The biochronologic and magnetostratigraphic studies provide reliable information for the chronology of various phases of faunal exchanges between north-western Africa and south-western Europe. Faunal exchanges took place 0.25 Ma before the Messinian Salinity Crisis. In addition, some of the taxa identified in AF12-2 (Myocricetodon, Protatera, Atlantoxerus), are useful as paleoenvironmental indicators, attesting warm and dry climatic conditions.

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This thesis dissertation is dedicated to the study of craniofacial structures within the hominid family. Throughout evolution, a reduction of facial prognathism and a diminution of the facial length are observed in the taxa which belong to the human lineage. This reduction of facial structures is associated to a more flexed cranial base and to a shorter mandible. The aim of this work is to define the role played by the basicranial and mandibular changes in the set up of the short and straight face of modern humans. In this context, the patterns of integration linking the face and the other cranial structures (basicranium and mandible) are decrypted and quantified in this thesis dissertation. This work has been done with a sample including all the extant hominid genera: modern humans, chimpanzees, gorillas, orang-utans. The skulls were first scanned using a medical scanner. Patterns of craniofacial integration were then studied using statistical tools and geometric morphometric analysis methods. This work underlined several mechanisms of craniofacial integration, unique to modern humans. These specific patterns of integration can explain an important part of the set up of modern humans reduced face. Thus, these results enlighten the evolution mechanisms and the set up of facial structures in hominids and in the human lineage.

  • Completed on: December 20 2013
  • PhD Student: Jacqueline NTSAMA ATANGANA
  • PhD supervisors: Patrick VIGNAUD (PALEVOPRIM), Emmanuel NDJENG, Mouloud BENAMMI (PALEVOPRIM), Joseph Victor HELL

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Hamakoussou and Mayo Oulo-Léré sedimentary basins are extension of the executive branch of East-West Yola Benue Trough, whose formation is related to the opening of the South Atlantic from the dislocation of Gondwana, in the Cameroonian territory. An age range of lower Cretaceous to Barremian-Hauterivian limit has been assigned based on biochronological studies. The sedimentary sequence in both basins is composed upward finnings fluivial to fluviolacustrine deposits. The deposits present an alternation of fine grained sandstone, siltstone and mudstone overlying coarse sandstone which is underlain by micro-conglomerate to conglomerate facies at the base.A magnetostratigraphic study has been carried out on a fine sediments in the upper part of each sections. 50 samples from about 69.03 m thickness, were collected from 11 sites at Djallou and 78 samples, about 511.03 m thickness, were collected from 20 sites at Ourokessoum localities in the Hamakoussou basin ; and 116 samples, about 478.19 m thickness, collected from 45 sites at Tchontchi locality in the Mayo Oulo-Lere basin.Specimens subjected to progressive alternating field and thermal demagnetization show that the sedimentary sequences have a primary magnetization. The directions of magnetization indicate a regional tectonic marked by a rotation and translation block. Rock magnetic investigations reveal the presence of both high and low coercivity minerals. A sequence of three polarities was determined along each section of the Hamakoussou basin: one reversal polarity and two normal polarities, whereas two polarities: (normal and a reversal) were determined along Mayo section in the Mayo Oulo-Lere basin The three polarities sequences from the two sections from Hamakoussou basin are correlated with M1 and M3 Chrons and suggest an age between 125 and 128, 11 My. While the two polarities sequences from the Mayo Oulo-Lere basin are correlated with M1 Chron, and suggest an age between 125 and 127.61 My. The sedimentation rates of Hamakoussou basin deposits vary between 5.5 cm/kyr and 40.88 cm/kyr and 38.26 cm/kyr in the section of Mayo Oulo-Lere basin.

  • Completed on: November 26 2013
  • PhD student: Alexis LICHT
  • PhD supervisors: Jean-Jacques JAEGER (PALEVOPRIM), Christian FRANCE-LANORD (ISTerre, Université de Grenoble)

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The fossil record of the first anthropoids is currently fed by several Middle to Late Eocene Asian strata (47 to 34 millions years ago), of which the Pondaung Formation in Myanmar has yielded the most diverse and prolific fauna. The aim of this PhD is to reconstruct the paleogeography, paleoenvironments, and paleoclimate of the Eocene Burmese successions in order to better constrain the early evolutionary history of the anthropoids. The sediment provenance of central Myanmar was first studied using a multi-proxy approach, combining petrography, sedimentology and isotope geochemistry. Results show that central Myanmar was isolated from any Himalayan or Tibetan input and additionally formed a narrow coastal band linking the Indian foreland with the Sunda area during the Eocene. Alluvial palaeoenvironments of the Pondaung Formation were then reconstructed through a combined sedimentological, pedological and paleobotanical approach. Results revealed a mosaic landscape with seasonal swamps, riparian forests, and open areas, expanding under a tropical climate with significant seasonality. Fossil woods form different ecotones similar to those of modern days monsoonal forests. Paleoclimate reconstruction through stable isotope geochemistry on mammalian fossil teeth and fossil gastropods confirms a monsoonal, modern-like rainfall regime in the Eocene. Pondaung paleoenvironments contrast with the idea of Eocene evergreen rainforests as a preferential living environment for the first anthropoids and link the Eocene biodiversity of anthropoid fauna to the tropical seasonal areas, where the biggest species, such as the amphipithecids, were particularly competitive.

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The subfamily Suinae is widespread in Plio-Pleistocene deposits in Africa, and was heavily used as a biochronological tool to correlate hominid-bearing sites based on the rapid morphological evolution of third molars in different lineages. A large sample of extant African suines enables to quantify patterns of variation in cranio-mandibular and dental morphology using geometric morphometrics. This modern referential is used to estimate the morphological variability in the fossil record. Revision of the paleobiodiversity of the genus Kolpochoerus (the most abundant Plio-Pleistocene suine) in Turkana and Awash basins is based on anatomical and morphometric studies of published and unpublished material discovered in the Lower Omo Valley (Shungura Formation) and in the Middle Awash Valley in Ethiopia. A new fossil species is described, evolutionary trajectories within each species are quantified, and biostratigraphic interpretations are revised. Phylogenetic relationships within the genus Kolpochoerus are described by the cladistic analysis. Paleoecological study of African suines is based on comparative anatomy and stable isotopic biogeochemistry (carbon and oxygen). Fossil suines display a wide range of body size, as well as various diets and habitats. The new results produced regarding their biodiversity, phylogeny, and ecology, enable to reconstruct a paleobiogeographic history of Suinae in Africa.

  • Completed on: December 6 2012
  • PhD Student: Alice NOVELLO
  • PhD supervisors: Patrick VIGNAUD (PALEVOPRIM), Doris BARBONI (CEREGE, Aix-en-Provence)

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This thesis dissertation is dedicated to the study of the phytolith signal of Mio-Pliocenesediments from Chad (Central Africa) dated between 7-2 Ma, and contemporary to the early Homininspecies Sahelanthropus tchadensis and Australopithecus bahrelghazali. A calibration work studyingthe relationship plants-phytoliths-soils in modern sub-Saharan tropical Africa was carried out in orderto assess the environmental significance of the phytolith signal in the fossil record. Phytolithassemblages produced by 98 sub-Saharan grass species (Poaceae) were analyzed and the results led tothe development of three new phytolith indices defined from 43 types specific to Poaceae. Tested on adatabase of 57 modern soil/sediment samples from Chad, these indices allow drawing aquatic grassassociations of Lake Chad, mesophytic grass associations of wetlands from the Sudanian domain, andxerophytic grass associations of drylands from the Sahelian domain. The analysis of modern soilphytolith assemblages (total assemblages) was used to assess the potential of this proxy to characterizethe physiognomy of the Sudano-Sahelian vegetation types. The calibration had been applied to thestudy of a discontinuous sedimentary record from Lake Chad (6-2 Ma) (Bol core, 13°N/14°E) and of18 paleontological levels from the Djourab (7-3.5 Ma) (16°N/17°E). The results indicate thedominance of intermediate to closed savannas and areas of aquatic vegetation at 7 Ma in the Djourab,and more open and dry savannas at 3.5 Ma. A limited lacustrine stage is recorded between 3.6-2.8 Maat Bol, and a shift of aridity at 3.2 Ma. Finally, the results show the existence of C4 grasses in Chadsince 7 Ma.

  • Completed on: October 26 2012
  • PhD Student: Noémie HAMON
  • PhD supervisors: Patrick VIGNAUD (PALEVOPRIM), Gilles RAMSTEIN (LSCE, Gif-sur-Yvette), Jean-Jacques JAEGER (PALEVOPRIM), Pierre SEPULCHRE (LSCE, Gif-sur-Yvette Cedex)

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Hominoids (apes) are the modern humans, chimpanzees, gorillas, orangutans and gibbons. They arose in Africa approximately 25 million years ago (Ma). Hominoids' evolution was punctuated by diverse dispersals between the African, European and Asian continents, which were made possible by the expansion of their habitat: subtropical and tropical forests. The aim of the present study is to understand the climatic changes that occurred during the Miocene (ca. 23 to 5 Ma) and to study their impact on hominoids' evolution.First, we focused on the middle Miocene climatic optimum (17-15 Ma), which coincides with the first hominoids' dispersal out of Africa, in particular the first occurrence of hominoids in the European fossil record. We then studied the impact of the Paratethys Sea retreat on regional climate and vegetation with an atmospheric zoomed model. Thirdly, we studied the middle Miocene climatic transition (approximately 14 Ma), which corresponds to a global cooling and East Antarctica ice sheet growth. We particularly focused on the impact of the East-Tethys seaway closure on oceanic circulation and climate. Then we ran a Tortonian (late Miocene, ca. 11 to 7 Ma) experiment to obtain a series of simulations representing the evolution of climate and vegetation during the Miocene. Finally, we used these simulations to force two ecological niche models in order to study the evolution of hominoids' potential distribution during the Miocene.

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Hyaenodontida and Carnivora are two carnivorans clades exhibiting an important taxonomic and ecological diversity in Paleogene and Neogene times, respectively. They are geographically widespread on all continents and their fossil record constitutes a useful tool for studies of biogeographical connections within and among continents. The geological timeframes in which Hyaenodontida and Carnivora are abundant are synchronous with the emergence of numerous mammalian orders and the diversification of modern mammals. The systematic study of Hyaenodontida of the Middle Eocene Dur At-Talah escarpment allows the description of the oldest species of Apterodontinae and several peculiar species of “Proviverrinae” Proviverra-like showing morphological affinities with contemporaneous European forms. The ensuing phylogenetical analysis proposes a close relationship between Apterodontinae and Hyainailourinae and confirms the hypothesis of an African dispersal into Europe at the beginning of the Oligocene. The study of Carnivora from the Middle Miocene basins of Southeast Asia results in the identification of new species of Amphicyonidae, Mustelidae, Viverridae, Herpestidae and Felidae. Biogeographical studies of localities of Carnivora from Souteast Asia, the Siwaliks, China and Japan are undertaken using similarity indices. The results show separate Southern Asian and Chinese provinces during the Middle Miocene, and separate Southern Chinese and Northern Chinese provinces during the Late Miocene. These results are discussed within the context of the tectonic and climatic history of Asia during the Miocene.

  • Completed on: December 10 2010
  • PhD Student: Diogo DE MAYRINCK
  • PhD supervisors: Paulo Marques MACHADO BRITO (UERJ, Brazil), Olga OTERO (PALEVOPRIM)

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The clade Otophysi, present nowadays on all continents, with the exception of Antartic, is formed by four distinct groups (cf. , Characiformes, Siluriformes, Gymnotiformes, and Cypriniformes). According to the last phylogenetic hypotheses this clade is supported by the presence of the Weberian Apparatus (cf. , modifications on the first occipital vertebrae creating a anatomical complex responsible for transmitting vibrations captured by the swimming blade to the inner ear) and a terminal vertebral centrum composed by the fusion of the preural 1 and ural centra. The present study presents an anatomical revision of certain fossil fish species (cf. , †Lusitanichthys characiformis, †L. Africanus, †Santanichthys diasii, †Chanoides weberi, †C. Chardoni, †C. Macropoma, †Salminops ibericus, and †Sorbinicharax verraesi) originally described as primitive Otophysi for possessing, among other characters, a Weberian Apparatus similar to the observed on the recent taxa. At the same time, this thesis made a revision of the characters used on the last phylogenetic proposal for Otophysi. The referred fossils were included in a phylogenetic analysis, alongside with species from each extant group of Otophysi, in order to test the position of those fossils in relation to each other and also to the extant groups. A parsimony analysis of a 90 characters confirmed the inclusion of these fossils within the clade Otophysi. The analysis also kept the monophyly of the genus †Lusitanichthys, allowed to question the monophyly of the genus †Chanoides, showed the genera †Salminops and †Sorbinicharax as a monophyletic group, and, finally, presented †Santanichthys as the sister group of the clade formed by the extant taxa, with the exception of Cypriniformes.

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During the past decade, new fossil discoveries from the African Paleogene and the Asian Neogene have provided new data that help reconstructing the early evolutionary history of several groups of mammals, including primates. The Asian and African continents have been both considered as major centres of evolution and diversification of primate groups during the Tertiary. However, understanding the early evolutionary history of these groups and the modes and routes of dispersal between these two landmasses have been hindered by a lack of consensus on both the timing and biogeography of their origins. New chronological data are absolutely required to provide a precise temporal framework, crucial for a better understanding of the early Tertiary emergence, diversification and paleobiogeographical history of the Asian and African groups of primates. The age estimates, provided by magnetostratigraphic and biochronologhical studies, have precised the age of several localities which document the poorly known Paleogene African mammal evolutionary history and contribute to illuminate the antiquity and the pattern of anthropoid radiation in Africa. This work, based on paleomagnetic and mammalian biochronological data, also presents refined chronostratigraphic analyses of the Khoratpithecus-bearing localities of Thailand and Myanmar. Providing a temporal framework for these deposits allows more precise correlations with other Neogene Asian hominoid localities, and permits a better comprehension of the evolution and paleobiogeographical patterns of Miocene South Asian mammalian faunas.

  • Completed on: November 25 2010
  • PhD Student: Thibaut BIENVENU
  • PhD supervisors: Michel BRUNET & Franck GUY (PALEVOPRIM)

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The fossil cranium of Sahelanthropus tchadensis, nicknamed Toumaï, was discovered in 2001 at Toros-Menalla (Chad). Currently, it is the oldest known hominid, dated at 7 Ma. It is very close, temporally and phylogenetically, to the dichotomy between humans and chimpanzees. Using synchrotron X-ray imaging techniques, fragmented inner table was virtually extracted out of the matrix filling the skull. Postmortem distortions of the endocranial surface have been corrected. Finally, filling the gaps resulted in the virtual endocast of the oldest known hominid. The endocast of Toumaï gives a first insight into the morphology of the brain of Late Miocene hominids. Comparison with a sample of extant and fossil primates, using both traditional and geometric morphometrics methods, enabled assessing primitive and derived endocranial traits of these hominids. The hypothetical endocranial morphology of the last common ancestor to humans and chimpanzees differs from those of extant great apes in many aspects, notably greater relative length, frontal lobes more stretched medio-laterally, and cerebellar lobes less protruding posteriorly, confirming that extant great apes are not good proxies to infer hominid primitive morphology. The endocast of Toumaï is characterized by a flexed cranial base and occipital lobes strongly protruding posteriorly. These structural changes provide new clues of the bipedal locomotor mode of Sahelanthropus tchadensis. The endocast of Toumaï does not show any clear feature of neural reorganization.

  • Completed on: December 2009
  • PhD Student: Soizic LE FUR
  • PhD supervisors: Patrick VIGNAUD (PALEVOPRIM), Emmanuel FARA (Laboratoire Biogéosciences, Université de Bourgogne, Dijon)

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Understanding past environments is a fundamental aspect of reconstructing the evolutionary history of living organisms. Accordingly, studying the paleoenvironment(s) associated with the earliest hominids makes it possible to define the environmental constraints under which the emergence of this group took place. The aim of this work was to reconstruct the paleoenvironment(s) associated with early hominids: Sahelanthropus tchadensis (7 Ma, Toros-Menalla, Chad), Orrorin tugenensis (6 Ma, Lukeino, Kenya), and Ardipithecus kadabba (5.77–5.54 Ma, Asa Koma, Ethiopia). To this end, the faunal structure (taxonomic and ecological structure) of the fossil mammal assemblages associated with these hominids, along with other Late Miocene African assemblages, was studied. Beforehand, it was essential to assess the representativeness of these fossil assemblages relative to the community or communities from which they originated. The study of the faunal structure of the Toros-Menalla assemblages revealed that they derived from a single paleocommunity, the faunal variations observed between assemblages being likely related to differences in depositional environment. A model was also proposed to explain the differences observed between the ecological structures of fossil faunas and those of modern faunas in terms of the underrepresentation of small species. With these prerequisites established, the analysis of faunal structure then made it possible to reconstruct, at Lukeino and Toros-Menalla, a mosaic of shrubby areas and more open wooded areas. Asa Koma appears to represent a more closed environment, consisting mainly of shrubby formations. This latter vegetational component thus appears to be an essential element for the presence of early hominids. These early hominids were, moreover, systematically associated with a particular combination of taxa (Orycteropus, Giraffa, Hystrix, Aepyceros, and Deinotherium), absent from other contemporaneous African localities.

  • Achevée le : décembre 2009
  • Doctorant : Edouard-Georges EMONET
  • Directeurs de thèse : Jean-jacques JAEGER & Franck GUY (PALEVOPRIM), Paul TAFFOREAU (ESRF, European Synchrotron Radiation Facility, Grenoble)

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La découverte d’hominoïdes fossiles en Thaïlande et au Myanmar a révélé de nouveaux épisodes de l’histoire évolutive du groupe. Ces fossiles ont été exhumés sur trois sites distincts, qui ont été caractérisés géologiquement et précisément datés : la mine de Chiang Muan, au Nord-Ouest de la Thaïlande, le plateau de Khorat, au Nord-Est de la Thaïlande, et la formation de l’ Irrawaddy, dans le bassin central birman. L’âge de ces sites est compris entre 8,8 et 13 Ma. La description des fossiles a permis leur attribution au genre Khoratpithecus, au sein duquel trois espèces ont été reconnues. Morphologiquement, Khoratpithecus présente des affinités claires pour le genre Pongo et, dans une moindre mesure, pour le genre Sivapithecus des Siwaliks. La morphologie des racines dentaires des hominoïdes a été étudiée grâce aux techniques d’imagerie numérique de la morphologie interne. Il est apparu que cette morphologie présentait une forte valeur taxonomique, et qu’elle était utilisable dans les analyses phylogénétiques. Une analyse morphométrique des couronnes dentaires, ainsi qu’une reconstitution virtuelle de fossiles déformés ou brisés, ont également été effectuées grâce aux techniques de microtomographie X. L’intégration des nouveaux fossiles et des nouvelles données dans les analyses phylogénétiques a confirmé la position de Khoratpithectus en groupe frère des orang-outangs. En revanche, le genre Lufengpithectus, classiquement attribué au clade Pongo, s’avère plus proche des Dryopithectus européens. Cette phylogénie renforce l’idée d’une migration d’ Ouest en Est, au sud de l’Himalaya, pour le clade Pongo, et une migration depuis l’Europe par le Nord de l’Himalaya pour le genre Lufengpithectus.

  • Achevée le : décembre 2008
  • Doctorant : Cyril CHARLES
  • Directeurs de thèse : Laurent VIRIOT (IJFL, ENS Lyon), Vincent LAUDET (ENS Lyon)

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Au sein des mammifères, les dents constituent un modèle idéal pour étudier les mécanismes liant évolution et biologie du développement. De nombreux gènes impliqués dans le développement dentaire ont été identifiés chez la souris. Cependant, leur implication dans les processus d’évolution reste en grande partie à étudier. Le présent travail a pour objectif d’évaluer le rôle de certains gènes dans l’évolution des dents chez les mammifères, plus particulièrement chez les rongeurs Muroidea. Dans une première partie, des anomalies dentaires rapportées dans des populations naturelles de mammifères sont présentées et discutées en regard des modèles de développement dentaire. Ces anomalies permettent également de souligner les différentes tendances évolutives chez les euthériens. La deuxième partie de ce travail comprend une étude des phénotypes dentaires associés aux pertes de fonctions de deux gènes de la voie Eda (Eda, Edar). L’étude de ces mutants permet d’apporter de nouvelles informations sur le rôle de ces gènes au cours du développement. Les résultats montrent également que la voie Eda est potentiellement impliquée dans l’évolution des rongeurs, en particulier dans l’acquisition de la formule dentaire des Muroidea. Les comparaisons morphologiques entre les mutants de la voie Eda et des espèces actuelles indiquent également une implication possible de cette voie de signalisation pour la mise en place de la morphologie dentaire particulière de Rhynchomys (Muridae, Rodentia). Enfin, une étude préliminaire de la morphologie dentaire des souris avec des pertes de fonction du gène Fgf3 et de ses antagonistes, Sprouty2 et Sprouty4, indique une implication potentielle de ces gènes pour l’acquisition du plan dentaire murin ainsi que des similitudes avec des espèces de Muridae primitifs. L’ensemble des résultats indique donc que les gènes du développement sélectionnés pour ce travail sont potentiellement impliqués dans l’évolution des dents des rongeurs Muroidea.

  • Achevée le : décembre 2008
  • Doctorante : Aurélie PINTON
  • Directeurs de thèse : Olga OTERO (PALEVOPRIM), Jean-François AGNESE (ISEM, Université de Monpellier), Didier PAUGY (BOREA, MNHN, Paris)

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Les découvertes récentes de faunes à hominidés dans le Mio-Pliocène d’Afrique de l’Ouest ont remis en cause le rôle de barrière joué par le rift Est-Africain et relancé le débat sur la paléobiogéographie africaine. Dans ce contexte, l’identification des barrières biogéographiques effectives à cette période est importante. L’une des contraintes à la dispersion des faunes est le réseau hydrographique. Cette thèse a pour objectif la reconstruction de la topologie de ce réseau durant le Néogène. Nous avons utilisé le genre de poisson-chat Synodontis (Mochokidae, Siluriformes) : la large répartition actuelle de Synodontis en Afrique, sa diversité importante, l’hétérogénéité des distributions de ses espèces actuelles, ainsi que son importante représentation dans le registre fossile sous-tendent une histoire complexe au sein du réseau hydrographique africain. Jusqu’à présent, l’identification des espèces de Synodontis était basée sur des caractères d’ anatomie molle. Nous avons établi un ensemble de caractères ostéologiques permettant la reconnaissance des d’espèces actuelles de Synodontis de la zone Nilo-Soudanaise. Cette étude anatomique a permis la reconnaissance des spécimens fossiles à un niveau spécifique dans le Mio-Pliocène d’Afrique (Tchad, Egypte, Tunisie, Uganda). Une phylogénie moléculaire est établie. Pour reconstruire l’histoire de Synodontis, nous avons combiné les approches anatomiques et moléculaires. L’évolution du groupe est structurée par la dorsale Centre Africaine et influencée par l’émergence du Rift. Nos résultats proposent une origine Congolaise de Synodontis dans l’Oligocène (~30 Ma). Subséquemment, des dispersions en zone Nilo-Soudanaise et Basse Guinée sont enregistrées. La phylogénie de Synodontis soutient l’existence d’un réseau hydrographique qui s’étend de l’Est à l’Ouest de l’Afrique, indépendant du Nil, et qui a fonctionné jusqu’à ~10 Ma. Au Miocène Supérieur, la distribution des espèces de Synodontis en zone Nilo-Soudanaise est plus hétérogène qu’ actuellement. Au Plio-Pléistocène, les échanges entre les bassins de la zone Nilo-Soudanaise s’intensifient, entraînant l’homogénéisation de l’ichtyofaune.

  • Achevée le : décembre 2008
  • Doctorant : Renaud LEBRUN
  • Directeurs de thèse : Jean-Jacques JAEGER (PALEVOPRIM), Christoph ZOLLIKOFER (Department of Anthropology, Universität Zürich)

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Les récents progrès de la génétique du développement et de l’analyse du phénotype ont engendré un regain d’intérêt considérable pour l’étude de l’évolution du développement (evo-devo). Cette thèse présente une étude des relations entre ontogénèse et phylogénèse dans le sous-ordre des primates strepsirrhiniens. Ici, on s’intéresse au complexe cranio-mandibulaire, dont la croissance et le développement sont analysés à l’aide d’un ensemble d’outils dédiés de géométrie morphométrique. Une analyse comparative de l’ontogénie du crâne et de la mandibule est conduite sur un ensemble de dix espèces de strepsirrhiniens et de deux espèces d’haplorrhiniens. Les haplorrhiniens et les strepsirrhiniens diffèrent largement dans la direction, la position, et la longueur de leurs trajectoires ontogénétiques. Chez les lémuriens malgaches, il y a une plus grande diversité de direction, de position et de longueur des trajectoires ontogénétiques que chez les loriformes. De plus, on observe des différences importantes de grade allométrique parmi les espèces de lémuriens, et une plus faible variabilité au sein des loriformes. Une analyse comparative est conduite sur un échantillon de primates Eocènes adapiformes et de strepsirrhiniens actuels. Au sein des adapinés, une augmentation de taille via transposition allométrique caractérise la lignée des Leptadapis. Enfin, les adapiformes adapinés et notharctidés ont des trajectoires ontogénétiques plus longues en terme de quantité de changement de forme que les espèces de strepsirrhiniens actuels. Une tendance au raccourcicement des trajectoires ontogénétiques caractérise l’évolution des strepsirrhiniens. Ceci est lié à un contexte général d’augmentation de l’encéphalisation au cours de leur histoire évolutive.

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Laboratory Paleontology Evolution
Paleoecosystems Paleoprimatology
UMR 7262 CNRS

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Université de Poitiers – UFR SFA
PALEVOPRIM – UMR 7262 CNRS
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