Reptiles, a diverse team of air-respiration vertebrates, are characterized by their scaly skin, amniotic eggs, and ectothermic (cold-blooded) metabolism. They can be usually labeled into 4 living orders: Crocodilia (crocodiles and alligators), Sphenodontia (tuataras), Squamata (lizards and snakes), and Testudines (turtles and tortoises). key Reptil