Gliding between continents: a review of the North American record of the giant flying squirrel Miopetaurista (Rodentia, Sciuridae) with the description of new material from the Gray Fossil Site (Tennessee)
摘要
Flying squirrels (Rodentia, Sciuridae, Sciurinae, Pteromyini) have a long and complex history in North America. First recorded during the Late Eocene, they vanished during the early Late Miocene (at about 9 Ma) only to re-appear in the Pliocene and Pleistocene. The first flying squirrels to be recorded after this Late Miocene gap are surprisingly attributed to the Eurasian genus of giant flying squirrel Miopetaurista. These are just two specimens from Florida that purportedly belong to Miopetaurista webbi, an endemic species. In this work we review these occurrences and further describe a new specimen from the Early Pliocene (latest Hemphillian or early Blancan) Gray Fossil Site in Tennessee, which may represent the oldest record of the genus in North America. We ascribe this new material to Miopetaurista webbi and find that this species is probably closely related to Miopetaurista thaleri, the only known Pliocene Eurasian species. The occurrence of Miopetaurista in eastern North America is puzzling, as it is distant from the known geographical range of the genus and of that of its sister taxon, the extant Petaurista. We hypothesize that Miopetaurista, which was linked to warm forested environments, dispersed into North America via the Bering Land Bridge during the warm phases of the Early Pliocene in the context of a major faunal dispersal event involving many other taxa. Later climatic cooling isolated these squirrels in warmer refuges, such as Florida, until they finally became extinct during the Early Pleistocene.