Reptiles are a category of wild animals and are an incredibly diverse group of vertebrates (animals with backbones). Reptiles date from the time of dinosaurs, and those that live today include leatherback turtles, cobras, mambas, comodo dragons, Nile crocodiles, Nile alligators, saltwater crocodiles, chameleons, crested geckos, and more. Reptiles are cold-blooded, needing to regulate their body temperature with the heat from their surroundings. They have lungs for breathing and have mostly dry, horny, or scaly skin.