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Updated May 8, 2019 | Infoplease Staff

Stegosaurus

Stegosaurus. (c) Joe Tucciarone

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.