The term prehistoric reptile covers a broad category that is intended to help distinguish the dinosaurs from other prehistoric reptiles. As the dinosaurs, because of their long and successful reign for many millions of years, are almost exclusively dealt with in their own category of prehistoric life. The category covers all the non-dinosaurian reptiles which are often erroneously considered to be dinosaurs, such as the sea faring varieties of plesiosaurs and the flying pterosaurs. Also included are ancient crocodiles such as Deinosuchus.