Analysis of dental enamel thickness in bears with special attention to Ursus spelaeus and U. wenzensis (=minimus) in comparison to selected representatives of mammals

Abstract

Dental enamel thickness carries precious information about dietary habits and functioning of dentition in fossil species. In the present study we analyzed enamel thickness in ursids, including three fossil taxa: Ursus wenzensis (Early Pliocene), U. deningeri (Middle Pleistocene) and U. spelaeus (Late Pleistocene). Enamel of typical meat-eating carnivorans, artiodactyls, chiropterans and primates was also considered for comparison. Enamel thickness was measured using a planar method, and was scaled by body mass. Analyses showed a clear relationship between the enamel thickness and diet of the bear taxa analyzed. Observed differences in enamel thickness followed a general evolutionary tendency in ursids, relating to the transition from carnivory to omnivory and the increase in tough and abrasive plant products in their diet, especially in cave bears. Among largebodied ursids, U. spelaeus showed the thickest enamel while U. maritimus was characterized by very thin enamel layer to its body mass, which can be related to its exclusive carnivorous diet. A significant increase in enamel thickness from anterior to posterior teeth was found in U. spelaeus and U. arctos, but not in the domestic dog and U. wenzensis. This is concordant with the progressive increase in the contribution of posterior molars to tough food processing in the evolution of ursids.