With the echidna, Platypoda are the only egg-laying mammals. Family contains one extant genus with one species, and one or more ancient genuses. Semiaquatic, burrowing mammals inhabiting lakes and streams in Tasmania and eastern Australia, having brown fur, a sensitive, pliable bill shaped like that of a duck, webbed feet with venomous spurs in the male, a flattened tail, and laying leathery eggs with young sucking milk from the pores of milk patches.