Nonetheless, individuals vary considerably in size, ranging from  in head-body length, with a relatively short tail  long. Body weight varies from ; no other sigmodontine species has a maximum weight above . The fur is thick and coarse, with an almost uniform shade of dark grey or brown across the whole of the body, although slightly paler on the throat and underside.
Despite their size variation, individuals differ significantly in length, ranging from head-body to tail length. Body weight varies considerably; no other sigmodontine species has a maximum weight exceeding . The fur is thick and coarse, with a consistent dark grey or brown coloration across the body, although slightly lighter on the throat and underside.