One of the defining characteristics of reptiles is that every reptile is covered in scales. Scales are flat, thin, hard pieces that form a covering for reptiles. While fish have scales too, they are wet scales, unlike the dry scales of a reptile. These scales help to lock in moisture – that’s why you see many reptiles living in hot environments! A lizard is one type of reptile. They have four legs, ear openings, and moveable eyelids. Some have horns for protection, while others can inflate their bodies to squeeze between rocks and tight spaces. Crocodilians such as alligators and crocodiles have eyes and nostrils on the top of their heads. All crocodilians are carnivores, and they have large tails that they use for thrashing in defense.