Reptile is the common name for one of the main groups of land vertebrates. It is not used so much by biologists, who prefer more accurate terms.
The name “reptile” comes from Latin and means “one who creeps”. All living reptile species are cold-blooded, have scaly skin, and lay cleidoic eggs. Reptiles also share an arrangement of the heart and major blood vessels which is different from that of mammals.
The hind leg of an iguana, showing iguanas’ iconic scales.
Reptilian skin is covered in a horny epidermis, making it watertight and enabling reptiles to live on dry land, in contrast to amphibians, which live on land and in water and have smooth skin.
Excretion is performed mainly by two small kidneys.
Watersnake Malpolon monspessulanus eating a lizard. Most reptiles are carnivorous, and many primarily eat other reptiles.
Most reptiles are carnivorous and have rather simple and comparatively short guts, since meat is fairly simple to break down and digest. Digestion is slower than in mammals, reflecting their lower metabolism and their inability to break down and chew their food.
Their energy requirement is about a fifth to a tenth of that of a mammal of the same size. Large reptiles like crocodiles and the large constrictors can live from a single large meal for months, digesting it slowly.
The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger. Most typical sense organs are well-developed with certain exceptions, most notably the snake’s lack of external ears (middle and inner ears are present).
Reptiles are generally considered less intelligent than mammals and birds. The size of their brain relative to their body is much less than that of mammals. Crocodiles have relatively larger brains and show a fairly complex social structure. Larger lizards like the monitors are known to exhibit complex behavior, including cooperation. The Komodo dragon is known to engage in play.
Most reptiles’ vision is typically adapted to daylight conditions, with color vision and more advanced visual depth perception than in amphibians and most mammals. In some species, such as blind snakes, vision is reduced. Some snakes can sense the body heat of birds and mammals, enabling them to hunt rodents in the dark.
(edited from source)