was named by Peterson (1905)
["fosser"]. Its type specimen is CM 1217, a partial skeleton (cranium, the vertebral column, including eleven caudals, (the extreme tip of the tail is missing), both clavicles, and a fairly complete set of ribs), and it is a 3D body fossil. Its type locality is Pine Ridge Escarpment
, which is in a Harrisonian terrestrial horizon in the Harrison Formation of Nebraska.
It was recombined as Palaeocastor fossor
by Stirton (1935)
and Martin (1987)
; it was recombined as Fossorcastor fossor
by Xu (1996)