MORPHOTYPIC CHARACTERISTICS OF THE FOURTH PREMOLARS OF THE BROWN (URSUS ARCTOS) AND POLAR (URSUS MARITIMUS) BEARS (CARNIVORA, URSIDAE)
The structure of the upper and lower fourth premolars of the brown (Ursus arctos) and polar (U. maritimus) bears has been studied. Teeth morphotypes have been identified and described. Morphotype frequency is given both for individual samples and the species as a whole. The brown bear is revealed to show a greater degree of morphotypic variability of the premolars. The brown bear is characterized by a more complex structure of the corona compared to the polar bear. It also shows vaster geographic variation of the tooth index complexity. The brown bear populations from Hokkaido have the most complex p4 and demonstrate considerable morphotypic variability. Evolutionary changes of the last premolars in the Ursus subspecies are represented in grinding surface simplification, which is most strongly pronounced in U. maritimus. The teeth of the polar bear are generally better adapted to carnivory than the premolars of the brown bear. Due to fast adaptation to hypercarnivory, the U.maritimus premolars obtained a unique appearance and specific features. Both teeth provide enough information for a rather precise species identification of the two species under study.