Stegosaurus was a large armored plant-eating dinosaur that lived during the Upper Jurassic Period (155-150 million years ago) in what is now western North America. It had an unusually small head, and although an adult would have weighed over 4.5 metric tons, its brain would have weighed less than three ounces. This led to the suggestion that Stegosaurus was extremely dull-witted, but it was clearly a successful dinosaur, so its small brain obviously wasn’t a problem.
History
Stegosaurus skeletons were collected in Colorado in the 1870’s by two famous American paleontologists, Othniel Marsh and Edward Cope. There two men were fierce competitors, each trying to find more dinosaurs than the other. Because of this competition, many different species of dinosaurs were collected in Colorado, including skeletons of Stegosaurus, Apatosaurus, Diplodocus, Brachiosaurus, Allosaurus, and Ceratosaurus. These dinosaurs all lived in the Late Jurassic, with the meat eating Allosaurus and Ceratosaurus feeding on the herbivorous Stegosaurus, Apatosaurus, Diplodocus and Brachiosaurus.