Reptiles are clad in scales, shields, or plates, and their toes have claws; amphibians have moist, glandular skins, and their toes lack claws. Reptile eggs have a thick, hard, or parchmentlike shell that protects the developing embryo from moisture loss, even on dry land. The eggs of amphibians lack this protective outer covering and are always laid in water or in damp places. Young reptiles are miniature replicas of their parents in general appearance, if not always in coloration and pattern. Juvenile amphibians pass through a larval (usually aquatic) stage before they metamorphose (change in form and structure) into the adult form. Reptiles include alligators, crocodiles, terrapins, tortoises, turtles, lizards, and snakes; amphibians include salamanders, toads, and frogs.
Crocodillians like this Florida alligator have been around since the dinosaurs. They are osteoderms, meaning they have bony deposits in their skin, which forms an effective armor on their backs and tails.