The fossa (/ˈfɒsə/ or /ˈfuːsə/ ; Malagasy [ˈfusə̥] ; Cryptoprocta ferox) is a cat-like, carnivorous mammal endemic to Madagascar.It is a member of the Eupleridae, a family of carnivorans closely related to the mongoose family (Herpestidae).he fossa appears as a diminutive form of a large felid, such as a cougar, but with a slender body and muscular limbs, and a tail nearly as long as the rest of the body. It has a mongoose-like head, relatively longer than that of a cat, although with a muzzle that is broad and short, and with large but rounded ears.