Reptiles, a various group of air-respiratory vertebrates, are characterised by their scaly skin, amniotic eggs, and ectothermic (cold-blooded) metabolism. They are historically categorised into four residing orders: Crocodilia (crocodiles and alligators), Sphenodontia (tuataras), Squamata (lizards and snakes), and Testudines (turtles and tortoises)