Order of Crocodilia (crocodile, garhial, caiman, and alligator): 23 species
Order of Sphenodontia (tuatara New Zealand): 2 species
Order of Squamata (lizards, snakes and amphisbaenia ("worm-lizards")): about 7,900 species
Order Testudinata (tortoises, turtles, and terrapin): about 300 species
Experts say in his findings that some reptiles are more closely related to birds than they are to other reptiles (crocodiles are more closely related to birds than they are to lizards), many modern scientists prefer to make Reptilia into a monophyletic grouping and also include birds, which when it contains more than 10,000 species or species.