Reptiles are ectothermic, air-breathing vertebrates. They are covered with scales or plates, unlike mammals with hair or birds with feathers. They may be oviparous or viviparous. Like mammals, the embryo is enclosed in an amnion. Unlike amphibians, reptiles do not have a larval stage and do not undergo | Reptiles are ectothermic, air-breathing vertebrates. They are covered with scales or plates, unlike mammals with hair or birds with feathers. They may be oviparous or viviparous. Like mammals, the embryo is enclosed in an amnion. Unlike amphibians, reptiles do not have a larval stage and do not undergo |