There are more than 2700 species of snakes in the world. Snakes are one of the most characteristic groups of animals, with their long, legless bodies they are easily recognizable by most people. Some other groups of legless animals are sometimes confused with snakes, including legless lizards and a group of legless amphibians (amphisbaenians). Snakes, like their sister group, the lizards, are covered in scales. Unlike most lizards, snakes have long, forked tongues, no external ear openings, and no eyelids. All snakes also have extremely flexible jaws that allow them to swallow their prey whole. All snakes are carnivorous, although they prey on many different kinds of animals.