The Rio de Janeiro Spiny Rat is a forest rodent of southeastern Brazil. Its buff-colored back is finely streaked with dark brown, while its soft bristles give the coat a surprisingly non-spiny appearance.
The upperparts are ochraceous buff, finely lined with blackish brown, and fade toward the sides; the underside is white. The tail is brown above and white below.
It is regularly found in mature forest, especially in moist places near fallen trees. Shelters have often been recorded under boulders near water, as well as at tree bases and beside fallen logs.
The tail averages about 90% of head-and-body length and lacks a conspicuous tuft at its tip.
The narrow, soft spines are 16–19 mm long.
An extinction-risk assessment has not been added yet.