Mountain beaver: A primitive fossorial rodent

Abstract

As the largest mammalian order, rodents are nearly cosmopolitan in distribution, can exploit a broad spectrum of foods, and can often reach high population densities. One sole representative of the most primitive family of rodents, Aplodontidae, does not share some of these common rodent characteristics. The aplodontoid rodents in the family Aplodontidae and Mylagsulidae radiated during the Miocene from the Allomyinae family (Carraway and Verts 1993). The extinctMylagaulidae represents the earlier radiation of these rodents who exhibited great specialization (Carraway and Verts 1993). Unlike the other members of the rodent order, mountain beavers are not prolific breeders; nor are they broad-spectrum habitat invaders, retaining in theirmorphology the primitive condition of the massetermuscle originating entirely on the zygomatic arch. The mostly extinct Aplodontidae family is now made up of the monotypic genus Aplodontia which has been able to survive since the early Oligocene and in some areas is even considered a pest.