OLIGOCENE MAMMALS FROM THE HSANDA GOL FORMATION MONGOLIA

The Hsanda Gol and Loh formations of south-central Mongolia contain a diverse mammal fauna from the Oligocene-Miocene epochs. The fossils in this study are placed in orders Rodentia and Lagomorpha and show adaptations to an arid environment through hypsodont and lophodont tooth morphologies. The sediments of the Hsanda Gol Formation are indicative of an arid environment where the deposits were probably laid down in a playa lake setting. This arid climate developed after the wetter more humid Eocene epoch. The climate shift altered the faunas such that the smaller mammals prospered while the larger mammals either went extinct or migrated. A possible example of selection within the population of Cricetops was observed and may relate to regional volcanism.