The bristle-spined rat (Chaetomys subspinosus) is an arboreal rodent from the Atlantic forest in eastern Brazil.

[2] It was officially described in 1818, but rarely sighted since, until December 1986, when two specimens - one a pregnant female - were found in the vicinity of Valencia in Bahia.

[3] Since then it has been recorded at several localities in eastern Brazil, from Sergipe to Espírito Santo (there are no recent records from Rio de Janeiro), but it remains rare and threatened due to habitat loss, poaching and roadkills.

Both are South American hystricognaths with hairs modified as spines or quills.

A molecular phylogeny based on the mitochondrial gene coding for cytochrome b combined to karyological evidence actually suggests that Chaetomys is more closely related to the Erethizontidae than to the Echimyidae, although it branches as the sister group to the rest of the Erethizontidae.