A snake is an 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 the lack of eyelids, hind limbs and external ears. Snakes are found on every continent except antarctica and range in size from the tiny, 10 cm long thread snake to pythons and anacondas of up to 7.6 m (25 ft) in length.
The fossil record of snakes is poor because snake skeletons are typically small and fragile, making fossilization uncommon. However 150 million-year-old specimens readily identifiable as snakes with lizard-like skeletal structures have been uncovered in south america and africa. Fossil evidence suggests that snakes may have evolved from burrowing lizards, such as varanids or a similar group during the cretaceous period.
The skeleton of most snakes consists solely of the skull, hyoid, vertebral column, and ribs, though henophidian snakes retain vestiges of the pelvis and rear limbs. The skull of the snake consists of a solid and complete braincase, to which many of the other bones are only loosely attached, particularly the highly mobile jaw bones, which facilitate manipulation and ingestion of large prey items. Contrary to the popular notion of snakes being slimy because of possible confusion of snakes with worms, snakeskin has a smooth, dry texture.