Crocodiles are an extremely interesting species of semi-aquatic predators . These animals belong to the order of aquatic vertebrates and received the status of the largest individuals of the reptile species. Historically, crocodiles are considered the ancient descendants of dinosaurs, since this species is more than 250 million years old. By right, this species is unique, since for such a huge period of existence, its appearance has not changed. Surprisingly, according to the features of the internal structure, crocodiles have more in common with birds, although they are a reptile species.