Biostratigraphic significance of the root vole ( Alexandromys oeconomus ) for dating late Middle and early Late Pleistocene (MIS 8-MIS 3) Neanderthal sites in southern Poland

Determining the age of late Middle and Late Pleistocene (MIS 8-MIS 3) Neanderthal sites can be difficult as radiometry has limitations. Biostratigraphic methods can be used to overcome these difficulties. A species useful in these analyses is Alexandromys oeconomus (Pallas, 1776), which has a wide modern geographical distribution in the Northern Hemisphere. During the Pleistocene, its range significantly increased, occurring in large numbers both in interglacials and glacials. We distinguished Middle Pleistocene from Late Pleistocene and modern populations of this species based on temporal variation in the morphological structure of the first lower molar (m1) occlusion surface, and the relative proportions of the typical “ oeconomus ” and atypical “ gud ,” “ nivalis ,” and “ malei ” morphotypes. Our results showed that the mean values of metric parameters of the occlusion surface m1 of A. oeconomus varied over time. We found that this variation distinguisheed between populations of species from the late Middle Pleistocene (MIS 8-MIS 6) and early Late Pleistocene (MIS 5) from those from the Late Pleistocene (MIS 4-MIS 2), and some measurements and coefficients were correlated with climate-environmental changes. Using variation in A. oeconomus m1 morphology can be used as a tool in biostratigraphy requires further research including, among others, studies on how morphology varies between regions.