Changes in the morphology and morphological diversity of the first lower molar of narrow-headed voles (Microtus gregalis, Arvicolinae, Rodentia) from northeastern European Russia since the Late Pleistocene

We studied morphotypic traits and dimensions of the first lower molar (m1) of recent and Late Pleistocene narrow-headed voles (20 samples) from localities of northeastern European Russia (the NE Russian Plain, Timan Ridge, and northern Ural Mountains). A high diversity of m1 morphotypes was found, especially among voles of the Late Pleistocene. The shape of the anteroconid and the size of the m1 varied independently from each other. No stable time trends in the proportions of “archaic” gregaloid and “advanced” microtid morphotypes of m1 for the last 50 ka were found. The morphotypical traits of only the oldest samples dated to the Early Valdaian (Laya, MIS 4) or late Sula (Mezin, end of MIS 5) were noticeably different from others. Our results do not support the hypothesis that climate changes in the Late Pleistocene-Holocene are correlated with the morphology (including morphotypic diversity) of the anteroconid of the first lower molar. Recent and Late Holocene voles inhabiting tundra are not similar morphologically to the Late Pleistocene animals in the region.