The main objective of my thesis is to study the diversity dynamics of a group of ungulate mammals (the European endemic artiodactyls) during a major faunal and climatic change that took place in Europe 34 Ma ago. My PhD work is thus divided into two parts: i) an inventory and a review of the material conserved in the collections of the University of Sciences of Montpellier (dental and cranial anatomy), ii) an analytical work based on this first point aiming at testing and characterizing the impact of biotic and abiotic factors on the diversity dynamics of the group (PyRate software) during the Eocene / Oligocene transition. My PhD work is an integral part of the ANR DEADENDER project (DEclin des ArtioDactyles ENdémiques EuRopeens) focused on the Quercy phosphorite region in the South West of France, and also includes a paleontological field excavation/prospecting component.