Ancestral Northern Red-Backed Vole from the Early Pleistocene of Western Siberia

— Fossil red-backed voles (Clethrionomys, Rodentia) are studied from the Lower Pleistocene deposits of Western Siberia based on materials from Skorodum and Romanovo localities (Omsk oblast). Red-backed voles are found in association with archaic voles Microtus (Allophaiomys), Prolagurus, as well as Mimomys and Predicrostonyx. Tooth characters of the smaller red-backed vole have shown its affinity to the recent northern red-backed vole, C. rutilus. Some plesiomorphic morphological characters, such as lower hypsodonty, archaic position of the posterior root of m2, etc., indicate its ancestral position in relation to the recent species and substantiate its description as a separate species, Clethrionomys sibiricola sp. nov. The discovery of the ancestral form of the northern red-backed vole confirms the molecular genetic data on the divergence of Siberian and European species of red-backed voles of the genus Clethrionomys in the Early Pleistocene.