An updated biochronology of Ukrainian small mammal faunas of the past 1.8 million years based on voles (Rodentia, Arvicolidae): a review

The Pleistocene biochronology of Ukraine based on remains of small mammals was established in the late 20th century. The main biochronological criteria used at that time were based on temporal changes in the fauna composition and percentage differences between teeth morphotypes in voles (Arvicolidae). In the present paper, these criteria are supplemented by morphometric data of the occlusal surface and enamel thickness of the first lower molars. The obtained numerical indices allowed evolutionary changes for particular taxa within Arvicolidae during the Pleistocene to be established. Evolutionary changes within particular lineages (Allophaiomys‐Microtus s.l., Mimomys‐Arvicola, Borsodia‐Prolagurus‐Lagurus) are discussed. The chronological sequence of about 70 Pleistocene sites in Ukraine and adjacent countries was described based on using both old and new criteria and taking into account cyclic climatic changes. We use and update biochronological units, i.e. faunal assemblages (formerly faunal complexes), which are divided into several associations (composition of arvicolid taxa at a particular evolutionary level in reference faunas). Further correlation of Pleistocene deposits is also possible since some marine sediments in the territory of Ukraine contain arvicolid remains.