Squirrels (Rodentia, Sciuridae) from the Late Miocene Pavlodar fossil site in northern Kazakhstan: implications for cranial anatomy and evolutionary history of the early marmotine ground squirrel genus Sinotamias

Abstract

ABSTRACT Although sciurids are among the most distinctive rodents of the Neogene age in Eurasia and North America, there remain significant gaps in knowledge of their fossil record, particularly that of Central Asia. Here we report on Sciuridae specimens from the Pavlodar (Gusinyi Perelet) fossil site in northern Kazakhstan (western Siberia), which pertain to Sinotamias orientalis, a basal marmotine ground squirrel genus from the Middle Miocene – Early Pliocene of Eastern Europe and Eastern Asia. The new specimens document the previously unknown cranial (maxillary and palatine) features of Sinotamias, which confirms the distinctiveness of the genus from chipmunks (subtribe Tamiina), suggesting a close phylogenetic relationship between Sinotamias and basal extant Marmotina genera Ammospermophilus and Callospermophilus. We review the rodent assemblage of Pavlodar 1A and propose the latest Miocene, Baodean age for the locality, correlative to the late Turolian, 7.5–6.5 Mya.