The fossa is Madagascar's largest terrestrial predator. It resembles the South American jaguarundi, a slender and lithe cat-like animal. The body is slender, but the limbs are very muscular. The head is similar to that of a mongoose but with a broader muzzle. The eyes are a medium brown with pupils that contract to vertical slits. Its retractable claws, typical feline short-jawed head, frontal eyes and round ears make it look like a cat. The tail is cylindrical. Also, the anatomy of its sex-organs resemble those of cats. However, fossas walk on the soles of their feet (Plantigrade) rather than on their toes (Digitigrade) like cats. Due to its general appearance, it was originally classed as a felid. Its resemblance to cats, however, is a result of convergent evolution. It is classified as but different from all other viverrids. It has been described as having the appearance of a cougar, although considerably smaller. Head and body length is about 27.5 inches, and tail length about 25.5 inches. Adult weight can vary from 21 to 44 pounds. The coat is reddish brown to dark brown. The carnassial teeth are well developed and upper molars reduced. The claws are retractile and the feet webbed. The ankles are 'reversible,' enabling the animal to grasp both sides of a slender tree trunk with the hind feet and descend head first or jump to an adjacent tree. Females show genital mimicry of males.