The bristle-spined rat (Chaetomys subspinosus ) is an arboreal rodent from Atlantic forest in eastern Brazil. Also known as the bristle-spined porcupine or thin-spined porcupine, it is the only member of the genus Chaetomys and the subfamily Chaetomyinae. 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. 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.
Bristle-spined rats are named because the spines on the back are more bristle-like in texture than the spines on the rest of the body. They have long, naked tails which are not prehensile. Adult animals weigh around 1.3 kg (2.9 lb).
Their skulls are unusual in several ways. The eye socket is almost completely surrounded by a ring of bone. Incisors are distinctly narrow. Overall, the animal displays a mix of New World porcupine cranial characters, spiny rat cranial characters, and characters that set it apart from all other rodents.
The bristle-spined rat is restricted to remnant forests and forest edges in the Atlantic coastal forests on the east coast of Brazil. Its habitat is dwindling rapidly and the species may be vulnerable to extinction. It is classified as vulnerable by IUCN and endangered by USDI.
