VINOKUROVA M.A., TIUNOV M.P.
Zoologicheskiy zhurnal 2026; 105(3): 90-105
The morphotypic features of the occlusal surface of the first lower molar (m1) in the modern Maximowicz's vole (Alexandromys maximowiczii) from the Amur Region (395 specimens), as well as 620 specimens of the modern Eastern vole (Alexandromys fortis) from the southern parts of Primorsky Krai, were studied. The study included a traditional analysis of variations in the lingual and buccal sides of the anterior unpaired loop of the tooth and the structure of the fourth lingual reentrant angle. Based on the morphological classification table constructed, 72 morphotypes were identified for A. maximowiczii. Among the study samples of Maximowicz's vole, ten m1 with fusion of the anterior unpaired loop and the fifth triangular dentinal loop, similar to A. oeconomus, were recorded, as well as eleven m1 with a closed sixth triangular dentinal loop. Since the occlusal surface of m1 in A. maximowiczii shows structural variations identical to those of A. fortis, a comparative analysis of the variability of m1 in these two species was conducted. As a result, 15 morphotypes with identical structures were found in both A. fortis and A. maximowiczii. When identifying fossil m1 specimens, the dimensional characteristics of their chewing surfaces must be considered first of all. m1 specimens with similar morphotypes and overlapping dimensional characteristics fall into a "grey zone".
