Reptiles, a various group of air-respiration vertebrates, are characterized by their scaly pores and skin, amniotic eggs, and tortoise, ectothermic (chilly-blooded) metabolism. They can be customarily classified into four dwelling orders: Crocodilia (crocodiles and alligators), Sphenodontia (tuataras), Squamata (lizards and snakes), and Testudines