It lived about 165 million years ago, some 20 million years before its famous relative, "Stegosaurus" appeared in North America. At only 4.5 metres long, it was also much smaller than its famous cousin. Found in the Lower Shaximiao Formation, "Huayangosaurus" shared the local landscape with the sauropods "Shunosaurus", "Datousaurus", "Omeisaurus" and "Protognathosaurus", the ornithopod "Xiaosaurus" and the carnivorous "Gasosaurus".