Abstract
A new genus and species of aplodontid rodent, Proansomys dureensis, from the late Oligocene of the northern Junggar Basin of China is described. The new genus is referred to as Ansomyinae because the ectoloph on the upper cheek teeth, although not fully crested, has attained the same characteristic bucket-handle-shaped configuration as other members of the subfamily. It represents the earliest record of the subfamily yet discovered in Asia and is more plesiomorphic than species of the genus Ansomys in having a partly crested ectoloph, a lower degree of lophodonty, and less complex tooth basins (lacking accessory lophules). Proansomys has transitional features between Prosciurus and Ansomys, suggesting that the Ansomyinae derived from a group of aplodontids related to Prosciurus, as did other advanced aplodontid rodents. This provides new light on the paleobiogeography of the Ansomyinae.
Highlights
Mountain beavers of the subfamily Ansomyinae are small-sized aplodontid rodents, characterized by a bucket-handle shaped ectoloph on their upper cheek teeth
We describe a new genus and species of the basal subfamily Ansomyinae from the late Oligocene Tieersihabahe and Saerduoyila localities in northern Junggar basin of China
Proansomys dureensis is assigned to Ansomyinae because the ectoloph of upper cheek teeth, not fully crested, has attained the bucket-handle shaped configuration that is the most important diagnostic character of the subfamily as its name implies
Summary
Mountain beavers of the subfamily Ansomyinae are small-sized aplodontid rodents, characterized by a bucket-handle shaped ectoloph on their upper cheek teeth (in occlusal view the buccal margin of the ectoloph undulates as does the grip on the handle of a bucket). Until recently the subfamily comprised only the type genus Ansomys and was found primarily from the late Oligocene and the middle Miocene of Eurasia [1,2,3,4]. Though found across the Holarctic region, the evolutionary origins and biogeography of the group are still poorly known because of relatively few records and poor representation of some taxa [5]. We describe a new genus and species of the basal subfamily Ansomyinae from the late Oligocene Tieersihabahe and Saerduoyila localities in northern Junggar basin of China.
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