like other stegosaurians, "huayangosaurus" was a quadrupedal herbivore with a small skull and a spiked tail. "huayangosaurus" had the distinctive double row of plates of all stegosaurians. these plates rose vertically along its arched back. in "huayangosaurus", the plates were more spike-like than in "stegosaurus". like "stegosaurus" it had two pairs of long spikes extending horizontally near the end of its tail.