The rise of carnivoran mammals in Europe through the lens of body mass

Carnivoran mammals (cats, dogs, bears, seals, etc.) and their kin radiated during the Palaeogene, among other carnivorous clades (hyaenodonts, mesonychians, and oxyaenodonts). This radiation has often been framed as a competition ultimately won by carnivorans, but the data supporting this hypothesis largely originate from North America. We derive body mass (BM) from dental measurements in European hyaenodonts, mesonychians, oxyaenodonts, and carnivoramorphans ranging from the latest Palaeocene to the end of the Oligocene (MP 6-30; 57.2-23.3 Ma) and compare those with North American data. We show that European assemblages tell a different story, with a marked increase of the disparity of carnivoramorphan BMs at and after the Middle Eocene Climatic Optimum (MECO; 40 Ma), with no clear effect on hyaenodonts. The 'Grande Coupure' (Eocene-Oligocene transition, approx. 34-33.5 Ma) marks the onset of a progressive decrease in the mean BM of hyaenodonts, while carnivoramorphans continue their rise initiated around the MECO. The observed BM patterns therefore do not follow the expected double-wedge pattern of competitive replacement and are possibly best explained by climate change-induced biodiversity dynamics.