Fossil Fauna of Small Mammals from Imanay Cave, Southern Urals, Russia

The fossil fauna of small mammals from the Imanay cave deposits (53°02′ N, 56°26′ E), Southern Urals, Russia, was studied. Species of open habitats prevailed, the narrow-headed vole ( Microtus ( Stenocranius ) gregalis ) being dominant. Two types of fauna were identified that characterize its composition and structure at the end of the Late Pleistocene and, presumably, in the Early Holocene. A codominant species of the first type of fauna (lower and middle cave deposits) was the steppe lemming ( Lagurus lagurus ). This type was characterized by a sharp predominance (83.0–92.2%) of steppe species and a low proportion (1.5–3.9%) of forest mammal species. Open landscapes must have dominated and been common in the Late Glacial in the southern part of the Ural Mountains. The pika ( Ochotona sp.) co-dominated in the fauna of the second type (upper cave deposits), with relatively high proportions of forest species (14.3–21.4%) indicating the appearance of forest formations in the Late Glacial or Early Holocene in this area. Samples of the first lower molars of narrow-headed voles were characterized by a high proportion of teeth (>50%) with simple variants of the structure of the anteroconid cap (“gregaloid” morphotype). High proportions (up to 51.6%) of the “transiens” morphotype were recorded among the first lower molars of the steppe lemming. Among the teeth in the lower half of the cave deposits, rootless cemented first lower molars (m1) and third upper molars (M3) were found with wide merging triangles T4–T5 (m1) and T2–T (M3). This structure of the chewing surface of the molars was typical of the ancient voles Microtus ( Stenocranius ) gregaloides and M. ( Terricola ) arvalidens from the fauna of the first half of the Early Pleistocene and the second half of the Middle Pleistocene.