Been doing some research on Prodeinotherium and the relatives, for no reason. And somehow I came across some excellent new dinosaur illustrations on wikipedia. We have relatively strict rules for image inclusion, such as anatomical accurateness. However, apparently the images are highly accurate, and two are even based off of work by Greg Paul. One of these was a Tuojiangosaurus, and I wanted to verify that it followed what it was based on. Thus, I got on the google book for the Field Guide, and checked out Greg’s Tuojiang. There were other stegosaurs in the guide so i viewed them one at a time. Then I came across him Huayangosaurus. Immediately, there is something peculiar I noticed, tying in with some old posts of SVPOW. There was a tail club!
I found this interesting, and thus wanted to check out if this was an accurate portrayal of Huayang. Online many illustrations (presumably based on Paul’s skeletal) had these club, but there was a rarity of pictures of a Huayang skeleton. So I was wondering if anyone who reads this blog has anything to say about the antiquity of the tail club on Huayangosaurus.
Anyway, there are some interesting thing about how this relates to other thyreophorans. Scutellosaurus was likely an ancestor or close relative of the ancestral thyreophoran, and it had, true to its name, a covering of scutes. However, the tip of the tail is unknown, so there is little more it is involved in with this post. Later are genera such as Bienosaurus, Emausaurus, Lusitanosaurus, and Tatisaurus. But no tail is known from these either (as i recall). Scelidosaurus is next in the thyreophoran line, and sadly, the very end of the tail is unknown. But, based on the Sole specimen, the tail would have had scutes that get smaller toward the end of the tail, and maybe a scute at the end of the tail.
Now for a speculation. If there was a scute at the tail end, I predict that it evolved into a small club, before the stegosaur/ankylosaur split. Then at this split stegosaurs gradually became more slender and lost use for a club past Huayangosaurus. And ankylosaurs became more bulky and gained a larger club, before splitting, with nodosaurids evolving slenderer and gradually losing there club, and ankylosaurids becoming bulkier and possessing a larger tail club.
Of course my speculation is just that. And even if Scelidosaurus and Huayangosaurus had a club, that does not necessarily mean that a club was ancestral.