Dinosaurs Dinosaur is the name of large extinct reptiles of the Mesozoic Era, during which they were the dominant land animals on Earth. The term was proposed as a formal zoologic name in 1842 by the British anatomist Sir Richard Owen, in reference to large fossil bones unearthed in southern England. The various kinds of dinosaurs are classified in two formal categories, the orders Saurischia and Ornithischia, within the subclass Archosauria. The first recorded dinosaur remains found consisted of a few teeth and bones. They were discovered in 1882 in Sussex, England, by an English doctor, Gideon Mantell, who named them iguanodon. About the same time, other fo