Most lizards have legs, but some are legless. In addition, lizards have a pair of lungs, while most snakes have an elongated right lung and either no left lung or only a rudimentary one. Although snakes are legless, they are able to move about with ease. A snake backbone has from 200 to 400 vertebrae, depending on the species, which permits extreme flexibility. Snakes move forward by a sidetoside movement, or in a straight line by literally walking on their ribs.
All snakes can swim.
Snakes must swallow their food whole, and some can engulf animals three times the diameter of the snake's head. The lower jaws of snakes are loosely joined to the skull and the upper jaws are movable. The snake's teeth also help it swallow. The teeth are sharp and curve toward the rear of the mouth. They hold the prey and prevent its escape.