Reptiles, a various team of air-respiration vertebrates, are characterized by their scaly pores and skin, amniotic eggs, and ectothermic (cold-blooded) metabolism. They're typically categorized into 4 living orders: Crocodilia (crocodiles and alligators), Sphenodontia (tuataras), Squamata (lizards and snakes), and Testudines (turtles and tortoises)