Morphotypic Characteristics of the First Molar (M1) of the Brown Bear (Ursus arctos) and the Polar Bear (Ursus maritimus) (Carnivora, Ursidae)

• Published in: Biology bulletin of the Russian Academy of Sciences Vol. 49; no. 7; pp. 961 - 974
• Main Author: Gimranov, D. O.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.12.2022; Springer Nature B.V
• Subjects: Bears; Biochemistry; Biomedical and Life Sciences; Cell Biology; Ecology; Genetic variability; Incisors; Life Sciences; Predators; Premolars; Ursus arctos; Ursus maritimus; Zoology; morphotypes; polar bear; species differentiation; teeth; brown bear; variability; molar
• ISSN: 1062-3590; 1608-3059
• DOI: 10.1134/S1062359022070056

The structure of the first upper molar (M1) of the brown bear ( Ursus arctos ) and he polar bear ( U. maritimus ) was studied. Seven features of polymorphism were identified, and descriptions were given. The M1 in the mainland populations of U. arctos displays no high morphological variability, whereas the populations of U. arctos from Hokkaido are distinguished by a large number of rare morphotypes and a greater complexity. In general, the M1 in brown bears and polar bears is not a highly variable tooth character compared to the incisors and premolars. In evolutionary terms, variations in the M1 structure are rather weak in the genus Ursus . The brown bear is shown to be reliably distinguished from the polar bear based on the M1 structure. The polar bear teeth vary in a peculiar way that does not coincide with the traditional scenario of tooth change in hypercarnivorous predators. Ursus arctos has a large number of progressive features in the structure of M1, while M1 in U. maritimus combines both progressive and primitive traits, as well as some features characteristic of only this species.