Dental wear variation and implications for diet: An example from Eocene perissodactyls (Mammalia)

Plagiolophus minor and Palaeotherium medium (Perissodactyla, Mammalia) co-occur in the Late Eocene site of La Débruge, France. Plagiolophus survived the earliest Oligocene mammalian faunal turnover, the Grande Coupure, whereas Palaeotherium became extinct. The diets of these two species are investigated by studying wear facet formation and the mesowear and microwear of the molar teeth. The range of variation in dietary wear is low within each species for mesowear and wear facet formation, but there is a large degree of variation within species for microwear features. Both species show high occlusal relief, approximately 50% sharp cusps and 50% round cusps, a significant proportion of early buccal phase shearing wear, polishing of the wear facets and the presence of small pits, all of which typify leaf browsers today. The general morphology of the teeth also suggests that both were browsers, sharing important characteristics with browsing rhinoceroses and hyraxes. The presence of extensive lingual phase wear, produced by grinding, suggests that a small proportion of fruit was also consumed. Coarse scratches and large pits, which may be the result of eating fruits and hard seeds, are also microwear features common to both. Palaeotherium exhibits less late buccal and lingual phase wear than Plagiolophus both of which indicate that it ate less fruit. However, the greater number of microwear features in Palaeotherium, may result from a diet containing more abrasive material such as seeds from fruit. The additional evidence in Plagiolophus of crown cementum and a shallower occlusal angle, suggests that it may have eaten tougher but less abrasive food. These dietary differences may explain the differential extinction at the Eocene–Oligocene climatic event.