Stegosaurus stenops Gift of Michael H. Roth The stegosaurus was an herbivorous quadruped that lived during the upper Jurassic period, about 155 – 144 million years ago. The average stegosaurus was about 30 feet long, between 9 and 13 feet tall, weighed about 5.5 tons (11,000 pounds), and had a very small brain (about the size of a walnut). Stegosaurus lived on grassless savannas in what is now North America; many stegosaurus fossils have been found in Colorado, Utah, and Wyoming. The spikes on this dinosaur’s tail were used for protection, but scientists are still debating the use of the large plates that line the animal’s spine and give stegosaurus its name, which means “roofed lizard.” One theory suggests that the plates protected stegosaurus from predators and another proposes that they helped regulate body temperature. The Everhart’s stegosaurus is a cast of a fully articulated skeleton from the American Museum of Natural History in New York.

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