Echnidna (Australia, New Guinea, and Tasmania): It has a very distinctive spine. The echnidna is one of the two monotremes (egg laying mammals) living on the face of the earth, the other being the platypus. It lives alone most of the time, burrowing in the ground. Its main food is insects, which it catches easily with the help of its long, sticky tongue. A normal echnidna grows up to 18 inches long.