Triceratops was a large herbivorous horned dinosaur that lived during the very end of the Cretaceous Period (68-66 million years ago) in what is now western North America.
History
Triceratops is one of the very first dinosaurs to be discovered. A famous paleontologist, Othneil Marsh, working at Yale University, first described and named Triceratops in 1889. Many skeletons have been collected over the years since, and at one point, up to 16 species of Triceratops had been named, all from western North America. Our studies of modern large herbivores indicate that it is highly unlikely that so many species would occupy the same general area (Question: how many species of bison are living on the North American plains today?). Now we only recognize two species: The older is Triceratops horridus, which lived for about one million years, followed by Triceratops prorsus, which lived until the end of the Cretaceous, when it became extinct with the last dinosaurs.