The twelve original specimens were unearthed in 1982, the same year I was born, that is pretty interesting and a small fun fact. Unfortunately, none of those twelve individuals consisted of complete specimens. The fact that twelve were found all together is, in itself, quite intriguing. Typically we don't see Stegosaurus traveling in herds in the fossil evidence or in the documentaries we have available, however, is it possible that Huayangosaurus was a herding animal? I wonder if this has been looked into or if it is considered a washed out area where bodies collected during a flood or something. Then again, if it was a wash out from a flood there would be other dinosaurs present too, so I may have just answered that question for good. Regardless, they collected for some reason and sudden death in a flood or mudslide or avalanche could account for this, I cannot tell anyone what it was because I have not found mention of the soil particulates that made up the rocks of the find, and this collection, I am willing to bet, was, if not herding behavior, at least a giant get together for the purposes of little stegosaurian love.