Snake

Snakes are limbless reptiles of the squamate suborder Serpentes. Closely related to lizards and the tuatara, snakes are ectothermic, amniote, air-breathing vertebrates with an elongated rope-like body covered by overlapping scales, and they move around using undulatory, rectilinear, concertina, sidewinding or slide-pushing locomotion, with some arboreal species even capable of short-ranged gliding flight by flaring out the ribs to flatten and widen the body for aerodynamic lift. Snakes have skulls with significantly fewer sutures and more hypermobile articulations (i.e. cranial kinesis) than their lizard relatives, enabling them to greatly widen the mouth and swallow prey much larger than their heads. To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most only have one functional lung. Despite being tetrapods from a cladistic prospective, snakes lack limbs completely, although pythons and boids retain a vestigial pelvic girdle. Some lizards have also independently evolved a snake-like elongated body without limbs or with greatly reduced limbs at least twenty-five times via convergent evolution, leading to many lineages of legless lizards, who have eyelids, external ears and a fleshy non-forked tongue that snakes lack, although this rule is not universal. Snakes are mostly terrestrial with a cosmopolitan distribution, and extant species are found on every continent except Antarctica, and on most islands — exceptions include Ireland, Iceland, Greenland and the islands of New Zealand, as well as many small islands of the Atlantic and Central Pacific oceans. Additionally, secondarily aquatic groups such as the sea snakes are widespread throughout the Indo-Pacific regions, while water snakes are found worldwide. Around thirty families are currently recognized, comprising about 520 genera and about more than 4,170 species. They range in size from the tiny, 10.4 cm-long (4.1 in) Barbados threadsnake to the reticulated...