Abstract
The Eocene-Oligocene transition (EOT) is a period of global environmental change particularly marked in Western Europe that coincides with a spectacular faunal turnover called the Grande Coupure. European endemic artiodactyls (EEA), which evolved in an insular context until the end of the Eocene, are strongly impacted during this period. The objectives of this thesis are: i) to determine the diversity dynamics of EEA around the TEO by identifying the role of abiotic and biotic factors on their diversification; and ii) to clarify phylogenetic relationships within EEA. The multi-site Konzentrat-Lagerstätte in the Quercy region (southwest, France) allows us to analyze the diversity dynamics of European artiodactyls on both sides of the TEO and to reconstruct their diversification history at the specific and generic levels using a Bayesian approach under a birth-death model (PyRate software). The results show an extinction of 80% of the EEA during the TEO. This drastic drop in diversity had not been previously identified and seems to be significantly correlated with abiotic factors such as temperature, sea level and organic carbon levels. The artiodactyl results argue against an extinction of endemic taxa through active competition with Asian immigrants and instead suggest that endemic forms became extinct prior to the arrival of immigrants from Asia. Moreover, surprisingly, they reveal that some endemic families may have even facilitated immigrant diversification. The detailed resolution of the Quercy fossil record allows us to describe the interactions between families in unexpected detail. The results highlight the complexity of inter-clade interactions and strong intra-clade competition, and show that some families appear to be crucial for environmental and food web structuring. The results also highlight that some "key" or "innovative" traits probably played a role in the survival of several endemic species during and after the crisis. The phylogenetic analyses performed then resolve the relationships within the superfamily of Cainotherioidea and the whole of EEA. The revision of the systematics and dental nomenclature of the Cainotheriidae and the description of a new taxon allow us to propose the first formal phylogeny of Cainotherioidea and to better understand the establishment of the unique dental pattern of Cainotheriidae. The construction of an original taxon/dental character matrix integrating a broad taxonomic sampling of EEA then allows us to propose one of the first comprehensive phylogenies of the latter. The topology of the strict consensus presents a large clade integrating all EAA species and splitting into two monophyletic groups: the first comprising the Choeropotamidae, Cebochoeridae, Dichobuninae, and the genera Aumelasia, Protodichobune, Buxobune, and Hallebune; and the second comprising successively the Hyperdichobuninae Amphimerycidae, Xiphodontidae, Anoplotheriidae, Mixtotheriidae, and Cain otherioidea. Most (sub)families of EEA are supported by dental synapomorphies with the exception of Choeropotamidae, Hyperdichobuninae, Amphimerycidae and Dacrytheriinae. The highly derived position of the genera Cuisitherium, Lophiobunodon and Dichobune in the topology calls into question the age of the initial radiation of the endemic European artiodactyls and places it at the end of the Lower Eocene. My thesis thus underlines the exceptional character of the Quercy phosphorites and is part of a historical continuity of Quercy research, proving that even 150 years after their discovery, Quercy remains a unique source of new data.