Remains of the Baikal yak (Poehpagus mutus baikalensis N. Verestchagin, 1954) from Late Pleistocene localities of Southern Siberia

136 bones of the postcranial skeleton and a part of the skull of a female Baikal yak (Poephagus mutus baikalensis N. Verestcthagin, 1954), originating from 18 cave locations and open-type Paleolithic sites in Altai-Sayan, Transbaikalia and Central Mongolia were examined. The material includes 38 metacarpals and 9 metatarsals of the yak. Morphometric differences in the structure of the postcranial skeleton of the yak and the bison (Bison priscus Bojanus, 1827) were revealed. The body size of the Baikal yak significantly exceeded that of the wild Tibetan yak (Poephagus mutus Przewalski, 1883). The largest representatives of P. m. baikalensis inhabited the Altai Mountains. In most of the sites, located in the mid-mountain landscapes of Southern Siberia (with absolute heights of 500–700 m), only a few remains of the Baikal yak were found, accounting for 0.01% to 1–2% of the number of megafauna remains. Most likely, herds of yaks did not live here permanently, but appeared only sporadically, during seasonal migrations. In higher mountainous areas (from 1000–1500 m) of Gorny Altai and Khangai Mountains in Central Mongolia, the proportion of the remains of the Baikal yak increases significantly – up to 16–22%. Like the contemporary P. mutus, the Pleistocene yak found its ecological optimum in the high-mountainous parts of ridges and mountain plateaus, dominated by cold, dry mountain-steppe landscapes with herb-grass vegetation and a small amount of snow. During the periods of cryochrones, the area of P. m. baikalensis apparently expanded significantly, incorporating the adjacent foothill territories. During the periods of thermochrones, it was most likely limited to the high-mountainous areas of the mountain uplifts of Southern Siberia.