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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 bear witness to a highly dynamic period in mammalian evolution. Many clades of modern mammals originated in this biogeographic region or underwent major radiations there. The main objective of my thesis is to characterize the ecological and environmental contexts in which the radiations of anthropoid and hominoid primates took place, particularly with respect to seasonality, vegetation, diet, and niche partitioning. To this end, I focused on two fossil mammal assemblages from the central Myanmar basin representing two key periods in primate evolutionary history, the middle Eocene and the late Miocene. The middle Eocene is an example of a globally warming world. The Pondaung Formation (Fm.) makes it possible to explore ecosystem dynamics within the faunal assemblage of a habitat that supported a large number of different early anthropoid primates. Previous studies have focused on the climate and vegetation of the Pondaung environment. I worked not only on climatic and environmental aspects, but also on the structure of micro-habitats across the different localities of the Pondaung Fm. and their use by different taxonomic groups. Based on this work, I was able to infer ecological flexibility for certain anthropoid primate species, based on their presence in different micro-habitats. The second focus of my work on the Pondaung fauna concerned a detailed reconstruction of the paleoecology of anthracotheres, and the dynamics of competition among the five species present.

The second mammal assemblage studied provides new insights for better understanding the evolutionary ecology of Ponginae in Southeast Asia. Today, only a single genus (Pongo) exists, whose geographic distribution is strongly restricted to the islands of Borneo and Sumatra. From the Miocene to the Pleistocene, species diversity and geographic range were much more extensive. The late Miocene Irrawaddy Fm. provides an example of the habitat of the sister group of modern orangutans, Khoratpithecus. I characterized the habitat of this fossil pongine by reconstructing its seasonality, vegetation structure, and niche-partitioning dynamics. I then focused my work on the question of ecological continuity within the pongine clade since the Miocene, by comparing different taxa from South and Southeast Asia.

As part of this thesis, I used two different analytical approaches. Here I present the analysis of stable isotopes (carbon and oxygen) and subsequent niche modeling of the Eocene and Miocene fossil assemblages from Myanmar. In addition, I studied dental microwear textures in pongines to gain more detailed insight into their evolutionary ecology, comparing the subsistence strategies of Miocene pongines with those of Pleistocene and present-day orangutans. Through the different approaches used in my thesis project, I was able to show that it is possible to push the boundaries of stable isotope niche modeling by using different isotopes that represent distinct ecological characteristics, and by applying new ecological approaches to the paleontological context. One example is the assessment of competitive potential dynamics within the anthracothere assemblage of the Pondaung fauna. The work on the orangutans of the Selenka collection was another way for me to bridge the gap between paleontology and the ecologists and biologists working on extant primate faunas, by providing a dataset that opens up new research directions in both fields.

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The Plio-Pleistocene witnessed crucial climatic and ecosystemic changes that coincide with key events in human evolution, particularly in East Africa. In this context, the temporal, ecological, and behavioral implications of the shift in hominid diet toward tool-assisted consumption of animal tissue can be further investigated. In the Turkana region, the Shungura Formation, dated between 3.6 Ma and 1 Ma, although rich in fauna and artifacts, had never been studied from a zooarchaeological perspective. This thesis examines the taphonomic and paleoenvironmental contexts of the vertebrate assemblages contemporaneous with human occupation sites in this formation. The aim was to address the subsistence behaviors of early hominids and the ecological context of the Oldowan and of recently discovered Acheulean localities. Various taphonomic marks were documented on the bone material from Shungura and compared with experimental samples including anthropogenic defleshing marks, trampling marks, and crocodilian and carnivore marks. Anthropogenic activity was confirmed in Members F, G, and L (from 2.3 Ma onward). While debate remains over the differentiation of bone surface modifications, the geometric morphometrics-based approach was able to effectively discriminate between the two. The second part of the thesis focused on the paleoenvironmental data surrounding the emergence of the Oldowan at Shungura (Member F, 2.3 Ma), combining taphonomy, faunal composition data, and 3D dental microwear texture analysis (DMTA). The results suggest greater local-scale ecological variability in Member F compared with the underlying deposits.

  • 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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Throughout the Cenozoic, changes in dental morphology have been observed within several mammalian clades, such as ruminants, suids, and hominins. These modifications are often interpreted as reflecting adaptations to increasingly abrasive diets linked to aridification and the progressive opening of habitats. The end of the Pliocene and the beginning of the Pleistocene constitute a pivotal period in hominin evolutionary history, notably characterized by taxonomic diversity including both gracile and robust forms. Different strategies developed during periods of food scarcity may help explain this diversity and the partitioning of ecological niches among contemporaneous taxa, shedding light on the factors that favored the selection of robust craniomandibular and dental phenotypes. However, the ecologies of Plio-Pleistocene hominins remain poorly understood. In order to refine our interpretations of variation in craniomandibular and dental ecological indicators commonly used in Old World contexts, an experimental model based on a bunodont omnivorous mammal was developed. This thesis is thus based on nearly 200 domestic pigs distributed across some thirty different controlled-feeding experiments. Several craniomandibular and dental indicators were studied: dental micro- and mesowear, enamel biogeochemistry, and mandibular morphology. This work highlights the ability of these indicators to detect the consumption, at low to moderate proportions, of food resources with physical and mechanical properties similar to those of foods potentially targeted by hominins during periods of food scarcity (fallback foods): seeds, herbaceous plants, C4 plants, animal matter, and underground storage organs. Furthermore, some resources appear to leave more marked traces than others on craniomandibular and dental records, and appear to generate greater constraints on mastication and dental abrasion. The results obtained make it possible to propose future developments for better calibration of these ecological indicators, as well as to verify these experimental observations in present-day wild taxa. The study of dental microwear in extant suids, in light of the experimental results, reveals relatively subtle differences in dietary habits. Paleo-ecological inferences are then proposed for Kolpochoerus from the Shungura Formation (Plio-Pleistocene, Ethiopia) based on their dental microwear. These results contribute to a better understanding of the behavior of commonly used ecological indicators following the consumption of different resources, and provide new insight to refine our paleo-ecological inferences.

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As material studied by vertebrate paleontologists, fossilized skeletal tissues represent an original archive, rich in ecological and environmental information from ancient times. They also record information about life history and living conditions, and provide insight into the functional adaptations of organisms — essential elements for understanding biological evolution in relation to environmental change. These aspects are addressed in the thesis through the exploration and development of various methodological approaches.

The skeletal growth marks of freshwater actinopterygians and chelonians from intertropical Africa are considered as a potential marker of paleo-seasonality. Developing this tool requires building a reference framework based on extant species closely related to the fossil ones, and this is broken down into two complementary studies. In the first part, I demonstrate, based on the results of an experiment on three intertropical species (Polypterus senegalus, Auchenoglanis occidentalis, and Pelusios castaneus), that the seasonal growth of these species is controlled mainly by food abundance, and sometimes by water temperature. In the second part, I demonstrate that examining bone growth in wild individuals of Lates niloticus is indeed correlated with seasonal cycles. These initial results also help clarify future developments needed to calibrate this seasonality marker. The third part presents the sampling carried out for an application to the Shungura Formation (Plio-Pleistocene, Ethiopia), along with the first observations.

Based on a synthesis of crocodilian ecology and physiology, 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 tooth formation. In a first study, the oxygen isotopic composition of bulk enamel from fossils of the Shungura Formation is interpreted, providing information on the evolution of freshwater environments and their local diversity over two million years. In a second study, sampling dentine in series, preliminary results show fluctuations consistent with climatic seasonality for some samples. These initial data allow for the proposal of a protocol aimed at interpreting the recorded signal and discussing the assessment of diagenetic impact.

Finally, the study of the fine functional anatomy of external bone structures (morphology, articular facets, muscle insertions, proportions) of the appendicular skeleton allows inferences to be made about the locomotor mode and, more broadly, the paleoecology of Amphicynodon leptorhynchus (Carnivora, Arctoidea) from the Quercy Phosphorites (early Oligocene, France). In the first part, functional analysis of the hindlimb reveals adaptations for climbing and supports the conclusion of probable arboreality. In the second part, a paleoartistic reconstruction of Amphicynodon leptorhynchus is developed based on anatomical evidence and consistent with the environmental context.

A synthesis is proposed placing these methodological contributions in perspective with broader scientific questions on evolution within its environmental context, with particular focus on questions of seasonality and paleoecological inference.

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The Pleistocene fossil record of East Africa bears witness to a climatic aridification and an opening of landscapes relative to previous epochs. It was during the climatic instability of the Plio-Pleistocene transition that an abundant fossil record of cercopithecid monkeys was documented, taxa particularly well represented at Shungura. This fossiliferous formation of the lower Omo Valley (Ethiopia) is characterized by a precise chronostratigraphic framework spanning the entire Plio-Pleistocene transition. Shungura thus offers an ideal setting for the detailed study of the impacts of climatic change on faunas, particularly for organisms dependent on humid and wooded environments, as is the case for most representatives of the family Cercopithecidae (colobines and cercopithecines).

My thesis work therefore focused on the study of a relevant ecological indicator, namely locomotion. It drew on morphometric methods to assess the locomotor behaviors and preferred substrates of the Shungura cercopithecids, in order to then test hypotheses of ecological niche partitioning, an essential element for a comprehensive understanding of their ecological dynamics.

My research first addressed the colobine fauna, large fossil forms documented at Shungura through craniodental remains (Rhinocolobus and Paracolobus). However, no analysis of their functional anatomy had yet been undertaken. Following descriptions and multi- and univariate morphometric analyses of 38 postcranial remains (including a partial skeleton), my work characterized preferences for varied locomotor substrates and an enhanced climbing capacity in Paracolobus, as well as a preference for arboreal substrates and suspensory abilities in Rhinocolobus. Based on these inferences, ecomorphological analyses revealed ecological niche partitioning between these two monkeys. My research also demonstrated the presence of small arboreal colobines, similar to present-day African forms, in the most recent member of the formation. This supports the establishment of a modern-looking colobine fauna following the disappearance of large colobines around 1.5 million years ago, in addition to documenting the impact of climatic change on this fauna.

Secondly, the functional and locomotor capacities of Theropithecus brumpti, a cercopithecine abundant at Shungura, were reassessed based on the first descriptive and morphofunctional analysis of a partial hindlimb of this species. My results indicate a preference for terrestrial substrates in T. brumpti, as well as the use of crouching, a posture characteristic of the genus but whose identification from osteological correlates had until now remained debated. Building on this new investigation of the form-function relationships of the T. brumpti hindlimb, a functional analysis of 190 long bone remains from across the entire Shungura sequence was undertaken. This study made it possible to i) confirm the strong morphological proximity of the T. brumpti forelimb to that of mandrills, ii) inform new hypotheses regarding ecological niche partitioning between T. oswaldi and T. brumpti, and iii) identify the presence of modern-looking baboons in the most recent levels of Shungura.

Overall, my work has put into perspective the locomotor diversity of the Shungura cercopithecids through the ecological niche partitioning of its various representatives, and has documented their ecological dynamics through the establishment of an ecologically modern fauna after 1.38 million years.

Keywords: Plio-Pleistocene, ecomorphology, cercopithecids, Shungura.

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The global cooling and the alternation between glacial and interglacial cycles of the Early Pleistocene resulted in shifting patterns of steppe and forest environments, thereby promoting faunal turnover and dispersals, including that of the genus Homo. In paleoenvironmental interpretations based on faunal assemblages, cervids, among the most abundant mammals, have traditionally been considered forest-dwelling, but this paradigm does not reflect the true complexity of their ecological diversity. Textural analysis of 921 specimens representing the 5 extant cervid species with well-documented ecology allowed the establishment of a robust reference database and confirmed a significant link between dental microwear and plant resources. Analysis of 547 fossil cervids from 15 European localities highlights their considerable ecological diversity. Eucladoceros ctenoides and Metacervoceros rhenanus show dietary plasticity. Their analysis allows the identification of adaptive dietary responses to environmental changes linked to climatic oscillations. These two eurytopic cervids constitute key ecological indicators. The forest component traditionally inferred from cervid presence is here called into question, as cervids prove to be more ecologically diverse than previously assumed. Dental microwear texture analysis of cervids from European sites where the presence of the genus Homo has been proposed aims to identify the type of habitat potentially favorable to its dispersal across Eurasia.

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In mammals, teeth are an essential tool for the fragmentation and fracture of food. In turn, the mechanical properties of food exert a selective pressure on dental morphology. The aim of this thesis is to determine whether this adaptive signal can be detected from molar morphology in extant and fossil primates. To this end, the 3D dental topography of 31 extant primate species is studied using a combination of classical and original variables. A fossil colobine, Mesopithecus pentelicus from the latest Miocene of Pikermi (Greece), is also analyzed. The results are interpreted in light of dietary regime, as well as a novel categorization system assessing the mechanical fitness field for shearing, crushing, and "cracking" food. The selected variables make it possible to significantly distinguish dietary categories and fitness fields within the extant sample. They also predict that M. pentelicus had an intermediate dental morphology, and that it was capable of "cracking" hard foods while maintaining an adaptation for shearing tough foods. Furthermore, the new variables show that enamel crests are significantly sharper in species consuming tough foods, confirming their use as a shearing tool. In contrast, the distribution of enamel thickness appears to be more homogeneous in durophagous species, suggesting that the whole tooth constitutes the elementary "cracking" tool in primates.

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Tomography is used to gain a better understanding of the evolution of biological species by comparing anatomical elements of fossil species with those of extant species. This technique is well suited to the study of fossils because it allows internal structures to be observed without destroying the sample, at high resolution, based on contrasts related to the density of the constituent materials. The limitations of this technique for the discipline relate to the sometimes low contrast between sediment and bone, as well as a resolution (10 µm) that is sometimes insufficient. Computer-based processing of the resulting images makes it possible to obtain quantitative data or to reconstruct deformed objects.

  • 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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Since the 15th century, Italy has been a favored land for collectors—private individuals, some of whom very early on made their collections available to the public. In most cases, collectors gathered objects for reasons of power, politics, or religious affiliation, rather than out of a concern for conservation. However, the development of networks of sociability and trade in the 16th century turned cabinets of curiosities into a European-wide reality. Upon the death of collectors, some collections were sold while others were transformed into museums as early as the 17th century; still others, in the 18th and 19th centuries, gave rise to the collections currently held in secondary schools and universities. The history of European collections, including in light of the most recent evolution of museums, invites reflection on what collections can and should be today—both in terms of their conservation and the conditions of their study, and in terms of their openness to the public. Following major paleontological discoveries in Africa, and with the aim of managing and promoting the collections generated, many national museums have been established in capital cities and have shifted their museographic approach to become true "muséums" oriented toward the development of scientific research. It is also through these discoveries that the world at large, as well as Africans themselves, became aware of the diversity and immense natural and heritage wealth of this continent. Chad's paleontological collections are of very significant scientific interest, owing to their impact on our knowledge of the "Origin and History of the Human Family." Of more than 20,000 fossil specimens unearthed by the MPFT, 18,343 have been inventoried and digitized, including 316 type and figured specimens. A database of these type specimens was built using Access and made available online on the CNAR website, and catalogues were also compiled and printed in the course of this work. These collections today constitute one of the richest paleontological collections in Central Africa, particularly for the Mio-Pliocene period (7.3 to 3 Ma), and also generate an undeniable socio-cultural stake. Reflection has been carried out and avenues proposed to ensure not only a genuine conservation policy but also one of valorization, particularly toward the general public. Our thesis aims to contribute to the reflection on the future of African collections, and Chadian collections in particular.

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The Khok Sung sand pit, in Nakhon Ratchasima Province, which has yielded more than a thousand mammal and reptile fossils (skulls, isolated teeth, and postcranial remains), houses the richest Pleistocene vertebrate fauna in Thailand. The mammalian fauna described here in detail comprises at least 18 identified species (12 genera), including a primate as well as proboscideans, rhinoceroses, suids, bovids, cervids, and carnivores. It mainly includes taxa still represented today, along with a few taxa that are globally or locally extinct. Based on paleomagnetic data and faunal comparisons, the age of the Khok Sung fauna is estimated to be late Middle Pleistocene, around 188,000 or 213,000 years ago. Compared with other diverse Pleistocene faunas of Southeast Asia, the Khok Sung assemblage is characterized by an association of Stegodon-Ailuropoda taxa, comparable in this respect to the Tham Wiman Nakin site, which supports the hypothesis that Northeast Thailand was a biogeographic corridor belonging to the Sino-Malayan migration route, between southern China and the island of Java. Stable carbon isotope analysis from the enamel of fossil ungulates reveals niche partitioning both among mega-herbivores and within cervids. The enamel δ13C values also suggest that ruminants consumed a large proportion of C4 plants, indicating that grass-dominated grasslands were particularly widespread in Thailand at this time, when ecosystems were not yet subject to anthropogenic influence. Measurements of stable oxygen isotopes, obtained through serial sampling of large-mammal tooth enamel, together with cenogram analysis of the Khok Sung locality, reflect substantial seasonal variation in precipitation and temperature, associated with relatively humid climatic conditions.

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Equids, a group with a wide geographic distribution and emblematic of macroevolution, are extensively documented. Their taxonomy, however, remains highly contentious, resulting in numerous synonymies, generally due to a lack of information on the diagnostic value of morphological characters. African hipparions and Equus, represented mostly by isolated dental material, remain poorly known compared to North American and Eurasian taxa, whose specimens are often more complete. To determine the range of variation in dental characters (ontogenetic, intra- and interspecific variation, and premolars/molars), a geometric morphometric analysis combined with 3D imaging and/or biometric measurements is tested for the first time on extant Equus species. The results are then used to determine or revise the fossil material from Chadian hominid sites (fossiliferous areas dated to 7 Ma, 5.4 Ma, 4 Ma, and 3.6 Ma) and Ethiopian sites (Shungura Formation, spanning continuously from 3.6 Ma to 1.05 Ma and documenting the first appearance of Equus in Africa at 2.27 Ma). A phylogeny based mainly on dental characters is also tested, and serves as a basis for discussing the phylogenetic relationships and paleobiogeography of these taxa. A morpho-functional study, which will later be combined with other paleoecological analyses, uses equids (generally considered indicators of open environments but capable of exhibiting varied diets) as paleoenvironmental indicators. The study of equids is therefore important within a chronological framework encompassing notable faunal and environmental changes linked to 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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Northwestern Africa, or the Maghreb, occupies a particularly distinctive geographic position: although an integral part of the African continent, it possesses a northern façade integrated into the Mediterranean domain and a southern, semi-arid to arid domain. In the first part of this work, paleomagnetic and biostratigraphic studies based on rodent fauna were carried out on continental deposits from two Algerian basins (Tafna and El Eulma). The magnetostratigraphic study conducted in this work made it possible to precisely date the various fossiliferous localities and to correlate them with other Neogene basins of North Africa. In the second part, new paleontological surveys in the Aït Kandoula basin in southern Morocco led to the discovery of three fossiliferous localities dated to the terminal Miocene. These localities yielded a rich micromammal fauna associated with large mammal remains. The systematic study of the micromammals, and more specifically the rodents, from the two localities AF12-1 and AF12-2 made it possible to identify taxa with affinities to those of southwestern Europe. These two new sites provided new evidence regarding faunal exchanges between Africa and Europe. The genus Stephanomys, in particular, is reported for the first time in Morocco. The biochronological study, combined with the magnetostratigraphic study, allowed these localities to be precisely dated, thereby providing reliable evidence regarding the chronology of the various phases of faunal exchange between northwestern Africa and southwestern Europe. The first faunal exchanges took place 0.25 Ma before the Messinian salinity crisis. In addition, certain taxa identified at AF12-2 (Myocricetodon, Protatera, Atlantoxerus) prove useful as paleoenvironmental indicators, attesting to warm and dry climatic conditions.

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This thesis addresses the integration of craniofacial structures within the hominid family. Over the course of evolution, a reduction in prognathism and a decrease in facial length are observed in taxa belonging to the human lineage. This reduction in facial structures is associated with a more flexed cranial base and a more gracile mandible. The aim of this work is to define the role played by basicranial and mandibular changes in the establishment of the short, orthognathic face of modern humans. In this context, the patterns of integration linking the face to other cranial structures (basicranium and mandible) are described and quantified in this thesis. This work was carried out on a sample of skulls including all extant hominid genera: modern humans, chimpanzees, gorillas, and orangutans. The skulls were first digitized using a medical scanner. Craniofacial integration patterns were then studied using statistical tools and geometric morphometric analysis methods. This work highlights several craniofacial integration mechanisms specific to modern humans. These specific integration patterns largely account for the establishment of the reduced face of modern humans. These results thus shed light on the mechanisms of evolution and development 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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The Hamakoussou and Mayo Oulo-Léré sedimentary basins are continental sedimentary basins. They are located in Cameroonian territory, along the extension of the east-west-trending Yola branch of the Benue Trough, whose formation is linked to the opening of the South Atlantic following the breakup of Gondwana. The age of these basins is based on biochronological studies placing them in the Early Cretaceous. The sedimentary sequence is essentially the same in both basins, consisting of fluvial to fluvio-lacustrine deposits showing an alternation of sandstone, siltstone, and claystone. Paleomagnetic samples were collected from fine-grained levels located in the upper part of the sedimentary sequence at each section. In the Hamakoussou sedimentary basin, 50 samples from 11 sites, spanning a thickness of 69 m, were collected at the Djallou locality, and 78 samples from 20 sites, spanning a thickness of 511 m, were collected at the Ourokessoum locality. In the Mayo Oulo-Léré basin, 116 samples from 45 sites, spanning a thickness of 478 m, were collected at the Tchontchi locality. Progressive alternating-field and thermal demagnetization of these samples shows that the sedimentary sequences of these basins carry a primary magnetization. The magnetization directions revealed a regional tectonic pattern marked by rotational movement about the vertical axis and translational movement of blocks. The magnetic minerals carrying this magnetization are of low, medium, and high coercivity. A sequence of three polarities was determined along each section of the Hamakoussou basin: one reversed polarity and two normal polarities. In the Mayo Oulo-Léré basin, the Mayo section yielded two polarities, one normal and one reversed. The polarity sequence obtained for each section was correlated with the geomagnetic polarity time scale. The three polarities of the Hamakoussou basin sections were correlated with chrons M1 and M3, with an age between 125 Ma and 128.11 Ma. The reversal sequence of the Mayo Oulo-Léré section was correlated with chron M1, with an age between 125 Ma and 127.61 Ma. The sedimentation rate of the Hamakoussou basin deposits ranges between 5.5 cm/Ma and 40.5 cm/Ma, and is 38 cm/Ma in the Mayo Oulo-Léré section.

  • Completed on: November 262013
  • PhD student: Alexis LICHT
  • PhD supervisors: Jean-Jacques JAEGER (PALEVOPRIM), Christian FRANCE-LANORD (ISTerre, Université de Grenoble)

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The oldest known fossil anthropoids come from several Asian geological formations of Middle to Late Eocene age (47 to 34 million years ago), among which the Pondaung Formation (Myanmar) has yielded the most diverse fauna. The aim of this thesis is to reconstruct the paleogeography, environment, and climate of the Eocene of Myanmar in order to better understand their evolutionary history. First, the evolution of sediment provenance in central Myanmar was studied using an approach combining petrography, lithostratigraphy, and isotopic geochemistry. The study shows that central Myanmar remained isolated from any Himalayan or Tibetan sedimentary input and formed, during the Eocene, a coastal belt connecting the Indian foreland with the Sundaland region. The paleoenvironments of the Pondaung Formation were then reconstructed using an approach combining fluvial sedimentology, pedology, and paleobotany. These approaches reveal a landscape of seasonal swamps, riparian forests, and open areas, developed under a tropical climate with strong seasonality. The fossil woods identified represent various forest ecotones similar to those of present-day monsoon forests. Stable isotope analysis of fossil gastropods and mammal teeth confirms a precipitation regime similar to that of the modern monsoon. The paleoenvironments of Pondaung contrast with the idea of dense primary forests as the preferred habitat of early anthropoids, and instead link their biodiversity to seasonal tropical zones, where the largest species, such as amphipithecids, were particularly competitive.

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The subfamily Suinae is widely distributed in Africa during the Plio-Pleistocene and has been extensively used for biochronological correlation of hominid sites, based on the rapid morphological evolution of third molars across different lineages. Using a large sample of extant African suids, patterns of cranio-mandibular and dental morphological variation are quantified through geometric morphometrics. This extant reference framework serves to estimate morphological variability in the fossil record. The revision of the paleobiodiversity of the genus Kolpochoerus (the most abundant Plio-Pleistocene suid) in the Turkana and Awash basins is based on the anatomical and morphometric study 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. Kinship relationships within the genus Kolpochoerus are described through cladistic analysis. The study of the paleoecology of African suids is based on comparative anatomy and stable isotope biogeochemistry (carbon and oxygen). Fossil suids exhibit a wide range of body sizes, as well as varied diets and habitats. The new knowledge gained regarding their biodiversity, phylogeny, and ecology allows for the proposal of a paleobiogeographic history of the Suinae in Africa.

  • Achevée le : 6 décembre 2012
  • Doctorante : Alice NOVELLO
  • Directeurs de thèse : Patrick VIGNAUD (PALEVOPRIM), Doris BARBONI (CEREGE, Aix-en-Provence)

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Ce mémoire présente l’étude du signal phytolithique de sédiments mio-pliocènes du Tchad (Afrique Centrale) datés entre 7-2 Ma, et contemporains des Homininés anciens Sahelanthropus tchadensis et Australopithecus bahrelghazali. Une calibration de la relation plantes-phytolithes-sols pour l’Afrique tropicale subsaharienne actuelle a d’abord été réalisée pour apprécier la signature environnementale des phytolithes dans le registre fossile. L’analyse des assemblages phytolithiques de 98 espèces de graminées (Poaceae) a permis d’élaborer trois nouveaux indices phytolithiques à partir de 43 types propres aux Poaceae. Testés sur une base de 57 sols/sédiments modernes du Tchad, ces indices permettent de tracer les associations graminéennes aquatiques du Lac Tchad, les associations mésophytiques des milieux humides soudaniens, et les associations xérophytiques des milieux secs sahéliens. L’analyse des assemblages phytolithiques des sols/sédiments actuels considérés dans leur ensemble a permis d’évaluer le potentiel de ce proxy à caractériser la physionomie des formations soudano-sahéliennes modernes. La calibration a été appliquée à l’étude d’un enregistrement sédimentaire discontinu du Lac Tchad (6-2 Ma) (forage de Bol, 13°N/14°E) et à celle de 18 niveaux paléontologiques du Djourab (7-3.5 Ma) (16°N/17°E). Les résultats indiquent la présence de savanes intermédiaires à fermées et de zones de végétation aquatique dominantes à 7 Ma dans le Djourab, puis de savanes plus ouvertes et sèches à 3.5 Ma. Une phase de bas niveau lacustre est enregistrée entre 3.6-2.8 Ma à Bol, et un pic d’aridité à 3.2 Ma. Enfin, les résultats montrent l’existence de graminées en C4 au Tchad depuis 7 Ma.

  • Achevée le : 26 octobre 2012
  • Doctorante : Noémie HAMON
  • Directeurs de thèse : Patrick VIGNAUD (PALEVOPRIM), Gilles RAMSTEIN (LSCE, Gif-sur-Yvette), Jean-Jacques JAEGER (PALEVOPRIM), Pierre SEPULCHRE (LSCE, Gif-sur-Yvette Cedex)

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Les hominoïdes (Grands Singes), actuellement représentés par l’Homme, le Chimpanzé, le Gorille, l’Orang-outan et les Gibbons, sont apparus il y a environ 25 millions d’années (Ma) en Afrique. Leur histoire évolutive a été marquée par différentes dispersions entre l’Afrique, l’Europe et l’Asie, qui ont été possibles grâce à l’expansion de leur habitat : la forêt subtropicale à tropicale. Le but du travail présenté ici est de comprendre les changements climatiques qui ont marqué le Miocène (23 à 5 Ma environ), et d’étudier leur impact sur l’évolution des hominoïdes. Dans un premier temps, nous nous sommes intéressés à l’optimum climatique du Miocène moyen (environ 17-15 Ma), qui coïncide avec la première dispersion des hominoïdes hors d’Afrique, en particulier leur première occurrence dans le registre fossile européen. Nous avons ensuite étudié l’impact du retrait de la Paratéthys sur le climat et la végétation à l’échelle régionale grâce à un modèle atmosphérique zoomé. Dans un troisième temps, nous avons étudié la transition climatique du Miocène moyen (environ 14 Ma), période de fort refroidissement global et de croissance de la calotte de glace de l’Antarctique de l’Est. En particulier, nous avons testé l’impact de la fermeture du passage océanique de l’Est-Téthys sur la circulation océanique et le climat. Puis nous avons modélisé le climat et la végétation du Miocène supérieur (Tortonien, 11 à 7 Ma environ), et ainsi obtenu une série de simulations représentant l’évolution du climat au cours du Miocène.

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Les Hyaenodontida et les Carnivora connaissent une diversité taxonomique et écologique importante au Paléogène et au Néogène respectivement. Ils sont également présents sur tous les continents et constituent donc un outil incontournable pour les études biogéographiques à l’échelle intra- et intercontinentale. Les périodes géologiques pour lesquels ils sont abondants coïncident avec l’émergence de nombreux ordres de mammifères actuels d’une part, et avec la diversification des formes de mammifères modernes d’autre part. L’étude systématique des Hyaenodontida de l’Eocène moyen du Dur At-Talah a permis de décrire la plus ancienne espèce d’Apterodontinae ainsi que plusieurs formes singulières de « Proviverrinae » Proviverra-like montrant des affinités morphologiques avec des espèces contemporaines européennes. L’analyse phylogénétique effectuée permet de proposer une proche-parenté des Apterodontinae avec les Hyainailourinae et soutient l’hypothèse d’une dispersion d’Afrique vers l’Europe du genre Apterodon à l’Oligocène inférieur. L’étude des Carnivora des bassins du Miocène moyen d’Asie du Sud-Est a révélé plusieurs nouvelles espèces d’Amphicyonidae, de Mustelidae, de Viverridae, d’Herpestidae et de Felidae. En prenant en compte la diversité des Carnivora du Miocène d’Asie du Sud-Est et celle connue dans le Miocène des Siwaliks, de Chine et du Japon, des études biogéographiques basées sur les indices de similarité des localités à Carnivora ont permis de confirmer l’existence de provinces sud-asiatique et chinoise au Miocène moyen, et des provinces Chine du Sud-Chine du Nord au Miocène supérieur, liée à l’évolution tectonique et climatique de l’Asie durant le Miocène.

  • Achevée le : 10 décembre 2010
  • Doctorant : Diogo DE MAYRINCK
  • Directeurs de thèse : Paulo Marques MACHADO BRITO (UERJ, Brazil), Olga OTERO (PALEVOPRIM)

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Au cours de ces dernières années, de nouvelles découvertes dans le Paléogène africain et le Néogène asiatique sont venues combler de nombreuses lacunes dans notre compréhension de l’histoire ancienne des primates. Ces découvertes ont amené de nouvelles problématiques concernant la chronologie et la paléobiogéographie de ce groupe. L’Asie et l’Afrique sont considérées comme des centres importants d’évolution et de diversification des primates au cours du Tertiaire mais les conditions paléoenvironnementales qui ont contraint les différenciations initiales au sein de ce groupe, les événements et les modalités de migration ainsi que la chronologie des échanges fauniques entre ces deux continents restent encore à élucider. L’établissement d’un cadre temporel, essentiel à la compréhension de l’histoire évolutive des faunes, s’est donc avéré nécessaire. Les études paléomagnétiques et biostratigraphiques effectuées sur de nombreuses séquences paléogènes en Afrique du Nord ont permis de corréler et de dater avec précision certains gisements de mammifères et d’apporter des éléments de réponse pour comprendre à quelle occasion les premiers anthropoïdes sont arrivés en Afrique, par quelle voie de dispersion et quelles étaient les modalités des différenciations initiales au sein de ce groupe. Le Miocène d’Asie du Sud a connu l’émergence de primates hominoïdes affiliés aux orangsoutangs. En Asie du Sud-Est, ce groupe est représenté par le genre Khoratpithecus, récemment décrit en Thaïlande et au Myanmar dans le Miocène moyen et le Miocène récent. Les études magnétostratigraphiques et biostratigraphiques des sites à Khoratpithecus ont apporté des indications fiables quant à la chronologie des différentes phases de divergences et la diversification initiale des hominoïdes, ainsi que des réponses sur leur histoire paléobiogéographique et les relations entre le climat et l’évolution vers les formes actuelles.

  • Achevée le : 25 novembre 2010
  • Doctorant : Thibaut BIENVENU
  • Directeurs de thèse : Michel BRUNET & Franck GUY (PALEVOPRIM)

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Le crâne fossile de Sahelanthropus tchadensis, dit Toumaï, a été découvert en 2001 à Toros-Menalla (Tchad). Il s’agit du plus ancien hominidé actuellement connu, daté de 7 Ma. Il est très proche, temporellement et phylogénétiquement, de la dichotomie entre les humains et les chimpanzés. A l’aide des techniques d’imagerie par rayonnement X synchrotron, la table osseuse interne fragmentée a été extraite virtuellement hors des sédiments qui remplissent le crâne. La surface endocrânienne a ensuite été rétrodéformée afin de corriger les distorsions post-mortems. Enfin, les lacunes ont été remplies, livrant ainsi le moulage endocrânien du plus ancien hominidé connu. Le moulage endocrânien de Toumaï offre un premier aperçu de la morphologie encéphalique pour le grade des hominidés du Miocène supérieur. Sa comparaison avec un échantillon de primates actuels et fossiles, par des méthodes de morphométrie traditionnelle et géométrique, a permis d’évaluer les caractères endocrâniens primitifs et dérivés de ce grade. La morphologie endocrânienne supposée du dernier ancêtre commun aux humains et aux chimpanzés diffère de celles des grands singes actuels sur plusieurs points, notamment l’allongement général plus important, la forme moins arrondie des lobes frontaux et la faible protubérance postérieure des lobes cérébelleux. Cela confirme que les grands singes actuels ne constituent pas de bons modèles pour reconstituer la morphologie primitive des hominidés. L’endocrâne de Toumaï présente une flexion basicrânienne importante et une forte projection postérieure des lobes occipitaux. Ces deux réorganisations structurales s’ajoutent à la liste des caractères crâniens en faveur d’une locomotion bipède. L’endocrâne de Toumaï ne montre pas de signe franc de réorganisation neurale.

  • Achevée le : décembre 2009
  • Doctorante : Soizic LE FUR
  • Directeurs de thèse : Patrick VIGNAUD (PALEVOPRIM), Emmanuel FARA (Laboratoire Biogéosciences, Université de Bourgogne, Dijon)

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La connaissance des environnements passés représente un aspect fondamental dans la compréhension de l’histoire évolutive des êtres vivants. Ainsi, l’étude du(des) paléoenvironnement(s) associé(s) aux premiers hominidés permet de définir les contraintes environnementales dans lesquelles l’émergence de ce groupe s’est effectuée. L’objectif de ce travail était de reconstruire le(s) paléoenvironnement(s) associé(s) aux hominidés anciens : Sahelanthropus tchadensis (7 Ma, Toros-Menalla, Tchad), Orrorin tugenensis (6 Ma, Lukeino, Kenya) et Ardipithecus kadabba (5,77-5,54 Ma, Asa Koma, Ethiopie). Pour ce faire, l’étude de la structure faunique (structures taxinomique et écologique) des assemblages fossiles de mammifères associés à ces hominidés et d’autres assemblages africains du Miocène supérieur a été entreprise. Au préalable, il était indispensable de s’intéresser à la représentativité de ces assemblages fossiles par rapport à la/les communauté(s) dont ils sont issus. Ainsi, l’étude de la structure faunique des assemblages de Toros-Menalla a révélé qu’ils provenaient d’une même paléocommunauté, les variations fauniques observées d’un assemblage à l’autre étant probablement liées à des différences d’environnement de dépôt. Un modèle a également été proposé afin d’expliquer, par une sous-représentation des petites espèces, les différences observées entre les structures écologiques des faunes fossiles et celles des faunes modernes. Ces prérequis obtenus, l’analyse de la structure faunique a ensuite permis de reconstruire, à Lukeino et à Toros-Menalla, un mélange de zones arbustives et de zones boisées plus ouvertes. Asa Koma présenterait un environnement plus fermé, étant principalement constitué de formations arbustives. Cette dernière composante végétale semblait donc constituer un élément indispensable à la présence des hominidés anciens. Ces derniers étaient par ailleurs systématiquement associés à une combinaison de taxons (Orycteropus, Giraffa, Hystrix, Aepyceros et Deinotherium), absente des autres gisements africains contemporains.

  • 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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Gildas Merceron
Olivier Chavasseau
Franck Guy
Olga Otero

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