(c) Joe Tucciarone
Meaning of Name:“roofed lizard”
Size:9 meters long
Weight: 1.8 metric tons
Location: Colorado, Utah, Wyoming

The Stegosaurus had a brain the size of a walnut. Its brain was so small it is unable to coordinate the Stegosaurus's movements. These dinosaurs relied on a ganglia–a nerve center or “second brain” located in its hips–to make movement possible. But what the Stegosaurus may have been missing in brains was made up for in brawn-the long, swinging tail was studded with sharp spikes.

Smartest:Dinosaur Hall of FameEarliest Dinosaur: