Since the age of dinosaurs, animals have developed many defensive techniques, including one of the most prehistoric called dermal plates. As its name implies, dermal plates are areas of an animal’s skin that have hardened to form a layer of protection. (Epidermis is the outer layer of skin covering the dermis layer and other subcutaneous layers of skin.)
Dermal plates can take many different forms, varying from species to species. The tough, yet flexible, “armor” hide of crocodiles, caimans and alligators are one form of dental plates. The scutes that form the carapace of turtles and tortoises are different in appearance from the skin of an alligator, yet they, too, are dental plates that protect from predators and the environment. The outer shell of armadillos is constructed of dental plates, as was the skin for many dinosaurs like the famous Stegosaurs, according to scientists.
Though they clearly look and feel different from what humans traditionally picture when they think of skin, dermal plates can justifiably be regarded as skin. However, dermal plates are made of a combination of keratin, calcified layers (hardened by salt), and/or ossified layers (hardened cartilage).