A snake is a limbless, elongate reptile of the suborder Serpentes. Like all reptiles, snakes are ectothermic and covered in scales. All snakes are carnivorous and can be distinguished from legless lizards by their lack of eyelids, external ears, and vestiges of forelimbs. The 2,900 species of snakes spread across every continent except Antarctica ranging in size from the tiny, 10 cm long thread snake to pythons and anacondas over 7 meters long.