The fauna of small mammals from two new localities of the Chernyshev Ridge in the Polar Urals, near hydrothermal vents, has been studied. As a result, two phases of microteriofauna development have been identified. The first, the Late Glacial, is characterized by the absolute dominance of tundra and tundra-steppe species (89—94 %), reflecting the harsh periglacial conditions. The second is Holocene, with a predominance of forest (up to 43 %) and intrazonal forms (up to 45 %), with a low proportion of tundra and tundra-steppe (19—22 %). A comparison with the microtheriofauna of the foothills of the Urals and the Timan Ridge shows a similarity in the dynamics of the fauna from the Late Glacial to the boundary of the Middle and Late Holocene (~ 4200 cal. years ago). During the transition from the Middle to Late Holocene, when the warm conditions of the Atlantic period gave way to a pronounced Subboreal cooling, which led to greater climate continentality, onset of permafrost in the tundra, and southward retreat of forest vegetation, in the north of the Chernyshev Ridge the proportion of tundra and tundra-steppe species began to increase again, while in the south (~66—66.5° N) their share continued to decline. Despite climate fluctuations and shifts in vegetation zones, the thermal springs of Pymvashor did not have a noticeable impact on the faunal composition in any of the phases, and the modern rodent community of the site does not differ from that in the adjacent areas of the Bolshezemelskaya tundra.
I. Kryazheva (Tue,) studied this question.