 Winge used four specimens for his description, including two skull fragments and an isolated maxilla (upper jaw) from the cave chamber Lapa da Escrivania Nr.5 and a mandible (lower jaw) from Lapa da Serra das Abelhas, but the latter later turned out to be from a different species, probably "Gyldenstolpia fronto".Lund named the animal "Hesperomys molitor" and placed it in the same genus ("Hesperomys") as what is now "Pseudoryzomys simplex" and two species of "Calomys".