Dental microwear textures and dietary preferences of extant rhinoceroses (Perissodactyla, Mammalia)

Abstract

Rhinoceroses were conspicuous elements in Cenozoic ecosystems, and studying the ecological behavior of extant species might unravel the ecology of their fossil kin. Microwear as a short-term recorder may detect subtle variations in the diet. Dental microwear texture analysis (DMTA) is extensively used to infer paleodiets. Yet, regarding ungulates, most microwear studies have been conducted on artiodactyls, and more particularly on ruminants (i.e., foregut fermenters), which may not be good models for hindgut fermenters, such as rhinoceroses. Moreover, rhinoceroses display a specific enamel ultrastructure with vertical Hunter–Schreger bands and a peculiar mastication cycle likely to impact tooth response to wear. Here, we studied the DMTA of the five extant rhinoceros species (17 specimens of Ceratotherium simum, four of Dicerorhinus sumatrensis, 21 of Diceros bicornis, 14 of Rhinoceros sondaicus, and 5 of Rhinoceros unicornis) and built up the present dataset. In parallel, we also compiled a taxon-based dataset of consumed plants for each rhinoceros species. Accordingly, we propose to reclassify the Indian rhinoceros (Rhinoceros unicornis) from mixed-feeder to variable grazer. Significant discrepancies were found between grinding and shearing facets on molars and between species on a given facet. Plotting the percentage of anisotropic specimens against that of complex specimens for each species discriminated well the different diets on both facets. This unprecedented dataset on rhinoceros texture microwear confronted to detailed diets appears critical for future diet reconstruction of fossil rhinocerotoids.