Pacaranas are distributed throughout Western South American from Colombia to Bolivia and inhabit the slopes and valleys of rainforests in the Andes mountains. They are thought to be extremely rare, although some scientists speculate that this might be due to a lack of information about the animal's true habitat.

Pacaranas are the third largest living rodent with a head and body length ranging from 730-790mm and a tail length of about 190mm (Anderson 1984). Pacaranas have upper parts that are typically dark brown or blackish with two discontinuous white stripes along the back and a few rows of white spots down each side (Burton 1987, Anderson 1984). The ears are relatively short and curved, the upper lip has a deep cleft, and pacaranas have many long, greyish whiskers. The feet are plantigrade and there are four digits on each foot, each with a long and powerful claw.