FREQUENCY OF CEMENTUM DEPOSITS IN TERMINAL SYNCLINES OF EURASIAN REPRESENTATIVES OF THE TRIBE LEMMINI (RODENTIA, ARVICOLINAE)

摘要

The data for five contemporary representatives of the genus Lemmus and for the species of Myopus schisticolor (wood lemming) are presented. The influence of age, sex, and jaw side (right or left) on the frequency of cementum deposits in terminal synclines was studied in different Eurasian forms of lemmings from the tribe Lemmini Some distinctions in the frequency of the parameter studied between forms of lemmings were revealed. The dependence between the frequency of the studied parameter and sex and age was found. The gender x age interaction, differences in age dynamics of some forms were shown. Evolutionary trends of changing the frequency of cementum deposits in certain synclines within the genus Lemmus based on the comparison of own and literary data were revealed. For Eurasian representatives of the genus Lemmus among the considered parameters, the main evolutionary change from the Late Pleistocene to the present is an increase in the frequency of cementum deposits in the lingual terminal syncline of the first lower molar. Among modern forms, L. lemmus and L. s. sibiricus (Norwegian lemmings and nominative subspecies of Siberian lemming) are distinguished by the most advanced features of the parameter considered. According to this characteristic, L. portenkoi (Portenko's lemming) and M. schisticolor are at the level of Late Pleistocene representatives of the genus Lemmus.