Late Eocene Rodent radiations: North America, Europe and Asia

Abstract

A review of the middle Eocene through earlyOligocene history of rodents in North America, Europe and Asia shows different developments in the three areas. In the late Eocene of North America three new families and seven genera of uncertain familial position show considerable morphological diversity and experimentation in zygomasseteric structure and cheek tooth pattern. The European record documents endemism through the middle and late Eocene, with considerable generic diversity at the end of the Eocene within the pseudosciurids and theridomyids. The Asian record, less completely known, shows an Asian origin for the ctenodactylids, presence of an hystricomorphous group with possible ischyromyidcylindrodontid affinities, presence of the oldest known cricetid in the late Eocene, and some endemism but also probable North American contact in the late eocene and Oligocene.