Castoridae is a family of sciuromorph and sciurognath rodents characterized by their semi-hypsodont to hypsodont molars, with occlusal surfaces displaying transverse or oblique re-entrant valleys (=flexi; Korth 2001). This family has a holarctic distribution, and originated as a monophyletic group which does not appear closely related to other recent groups of sciuromorph and sciurognath rodents (Korth 1994).
Previous fossil records of numerous genera of castorids are known from Eurasia and North America, and date back to the latest Eocene (Wu et al. 2004). In contrast, today the castorids are represented by only two extant species of the genus Castor: Castor fiber and Castor canadensis. Four subfamilies are recognized by Korth (2001); Agnotocastorinae, Palae- ocastorinae, Castoroidinae, and Castorinae. The most com- mon fossil of the subfamily Castorinae in Miocene localities of Eurasia is Steneofiber, which is one of the earliest castorine that appears in Europe during the late Oligocene (Korth 2001; Stefen 2005). This genus is also supposed to be at the base of the radiation of later European beavers (Stefen 2005). Species