Snakes are elongated, legless, carnivorousreptiles of the suborder Serpentes. [2] Like all squamates, snakes are ectothermic, amniotevertebrates covered in overlapping scales. Many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads with their highly mobile jaws.

To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear in front of the other side of side by side, and most often only one functional lung. Some species retain a pelvic girdle with a pair of vestigial claws on either side of the cloaca.

Lizards have evolved elongate bodies without limbs, or with limestone, and have been reduced to about twenty five times through convergent evolution, leading to many lineages of legless lizards. [3] Legless lizards resemble snakes, but some common groups of legless lizards have eyelids and external ears, which are not universal (see Amphisbaenia, Dibamidae, and Pygopodidae).

Living snakes are found on every continent except Antarctica, and most of the smaller land masses; exceptions include some large islands, such as Ireland, Iceland, Greenland, the Hawaiian archipelago,