Stegosaurus

 

• Late Jurassic
• North America
• 30 feet long
• Was a member of the armored-dinosaurs, and was the largest and most familiar of the group. There are many theories about the plates on the back of these animals. These bony plates have never been found attached to the rest of the skeleton. Most think that they stood up vertically but some think they laid flat and were used as armor. Stegosaurus weighed about 4000 pounds. The skull was about 16 inches long and it contained a brain about the size of a walnut.