Stegosaurus was a plant-eating dinosaur that is best known for the two rows of large bony plates along its back. The plates looked like giant leaves and some were more than three feet long! Scientists believe that the plates helped heat and cool the animal. It was like dinosaur air conditioning! 

If the stegosaurus stood with its huge plates facing the Sun, the sunshine would warm up the blood inside the plates. That would then heat the rest of the animal as the blood traveled around its body.  The plates could also help cool the stegosaurus if it stood with its plates facing away from the Sun.

Stegosaurs weren't very fast movers, but luckily they did have a tail with long spikes that they could use for defense against meat-eating dinosaurs.