Late Pleistocene Taphocoenosis of Insects and Small Mammals from the Upper Reaches of the Ob River

A taphocoenosis including remains of insects and small mammals from the Quaternary deposits in the vicinity of the village of Kalistratikha (Altai Region, Russia) on the Ob River is revealed. The ¹⁴C dating of the deposits has shown 24.438 ± 0.350 ka. Insects are mostly represented by Coleoptera (59 species of 13 families) and dominated by species of Curculionidae, especially Otiorhynchus, and Carabidae. Otiorhynchus ursus, O. altaicus, and O. unctuosus are most abundant. The following 13 species are recorded in the Pleistocene deposits of Western Siberia for the first time: Bembidion tibiale, B. gebleri, Pterostichus drescheri (Carabidae), Centorus rufipes (Tenebrionidae), Stephanocleonus ?grigorievi, Aulacobaris violaceomicans, Tychius albolineatus, Zaslavskypera conmaculata, Hypera misella, Limobius borealis, Chlorophanus tuvensis, Otiorhynchus unctuosus, and Mesagroicus piliferus (Curculionidae). Small mammals are represented by a few fragments referred to as Sorex sp., Allactaga sp., Spermophilus cf. erythrogenys, Sicista cf. subtilus, Eolagurus sp., Lagurus cf. lagurus, and Microtus gregalis. Small mammals and insects are typical of open landscapes, such as steppes and meadows; riparian insects also occur in the taphocoenosis. The modern geographical range of the majority of species of the steppe assemblage covers central Kazakhstan and adjacent areas; three species of the taphocoenosis are endemic to the mountain depressions of the Altai, Tuva, and northern Mongolia. The majority of meadow and riparian species are boreal–mountain. Judging from the composition of the taphocoenosis, the climate was drier and colder compared to the modern one, but warmer and more humid than during the succeeding Sartanian stadial. Prevailing landscapes were probably dry steppes with meadow and shrubby (osiers) vegetation in the lowered areas. Forests were absent or played a minor role (sparse trees might have been present).