Variety of the Thyreophora

From shortest to longest (those of similar length are listed from back to front): Scutellosaurus lawleri, Scelidosaurus harrisonii, Huayangosaurus taibaii, Gastonia burgei, Edmontonia longiceps, Stegosaurus armatus, and Ankylosaurus magniventris

The thyreophorans, or armored dinosaurs, were a group of plant eaters that had evolved armor to defend against meat-eating dinosaurs. However, in stegosaur thyreophorans, the usual spikes and scutes (bits of keratin armor studded into the skin) had evolved into flat, upright plates (to be fair, some stegosaurs did have spikes, but they all had plates of some shape as well) that were ill-positioned and -shaped for protection, and may have played a part in species recognition.