Beavers (Castor fiber L.) of the Late Pleistocene of the southeast of Western Siberia

A comparison of morphometric data on the mandibles and femurs of fossil beavers from the Krasny Yar site (Tomsk region) and modern representatives made it possible to establish a very high degree of closeness of animal sizes. At the same time, a greater massiveness of the diastema area in fossil jaws was noted than in modern animals. The analysis of the multi-species locations of large mammals of different geological ages allowed us to establish the long-term habitation of Castor fiber in the southeastern part of Western Siberia during the Late Pleistocene. The geochronological distribution of beavers is well tied to the warm and humid intervals of the Late Pleistocene (MIS 5e and the first half of MIS 3). At the optimum of the Holocene, the beaver spreads north to 69 °C, and in the Late Pleistocene to 58 °C. The beaver, as a species with a narrow ecological valence, is a good bioclimatic marker for the Late Middle and Late Pleistocene, reflecting warm and humid environmental conditions close to modern ones. Based on the ecological features of modern beavers, it can be argued with a high degree of probability that during the geological periods of time in which beavers spread quite widely, there were several important paleogeographic features. There was necessarily a stable river flow with wide drainage of the territory, the presence of a large number of relatively small watercourses with stable hydraulic regime and the absence of a thick continuous ice cover on them during the cold period. Another important circumstance is the presence of a forage base in the immediate vicinity of the riverbed, which includes coastal tree and shrub thickets. Contribution of the authors: the authors contributed equally to this article. The authors declare no conflicts of interests

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