Stegosaurs have big bony plates on their backs and long spikes on their tails. Scientists aren’t quite sure why, but there’s a good chance they’re either there to defend against predators or attract mates. Their plates and spikes earned them a place in the dinosaur group Thyreophora, meaning “shield bearers.”
In addition to the stegosaurs, another group makes up Thyreophora: the ankylosaurs. Ankylosaurs were also four-legged herbivorous dinosaurs, but their armor is a little different. Instead of having tall bony plates on their backs, ankylosaurs had bony armor all along their bodies, including sometimes on their eyelids. And to top it all off, they had heavy clubs at the end of their tails!
Photo by Jeremy Knight