A long-bodied, limbless, carnivorous reptile (suborder Serpentes), with eyes covered by a transparent scale but lacking eyelids and external ears, and with jaws linked by ligaments that allow the animal to swallow items larger than its head. Paired organs are arranged one behind the other and there is only one lung. Most snakes have a forked tongue that they protrude through a notch in the snout. Most snakes are terrestrial but some are aquatic. There are 12 families with more than 2900 species found in all continents except Antarctica.