Reptiles, a diverse group of air-breathing vertebrates, are characterised by their scaly skin, amniotic eggs, and ectothermic (cold-blooded) metabolism. They can be usually labeled into 4 dwelling orders: Crocodilia (crocodiles and alligators), tortoise, Sphenodontia (tuataras), Squamata (lizards and snakes), and Testudines (turtles and tortoises).