There were many changes in the Thyreophora subgroups of the stegosaurs and ankylosaurs. In particular, few species of the stegosaurs survived into the Cretaceous period. The ankylosaurs fared much better, with the best-preserved fossils coming from Mongolia and China; others are also known from North America, Europe, and Australia. In fact, these plant-eating animals were so huge and heavily armored by the end of the Cretaceous period that they probably didn’t have to worry about predators at all.