Since Evolution is itself a theory, the detailed dinosaur classification system shown below is also theoretical -- based on certain assumptions and guesswork -- and thus will change. Dinosaur classification and the assumed number of dinosaur species may vary widely depending on the paleontologist.

The number of species shown below is approximate and obviously will change. (Click here to see why)

The dinosaurs are divided into two orders (Saurischia and Ornithischia) and six suborders (Theropods, Sauropodomorphs, Sauropods, Ornithopods, Stegosaurians, Ankylosaurs and Ceratopians).