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STEGOSAUR SHOULDER SPINES
<< 1. What stegosaurians are known to have had shoulder spines? The
genera I know of are *Huayangosaurus*, *Kentrosaurus*, *Lexovisaurus*,
In my wanderings with these guys, I have come to the conclusion that shoulder
spines are probably primitive for stegosaurs, and probably maybe even
thyreophorans as a whole, the only stegosaur that seems not to have had them
is Stegosaurus itself, and maybe Wuerhosaurus, which, conveniently clade
exclusively with eachother based on a myriad of other characters.
So, to answer the question, all stegosaurs had them EXCEPT Stegosaurus and
<< 2. What angle do the shoulder spines form with the long axis of the
body when seen in dorsal view, if known?>>
Um... The base is at a 45 degree angle roughly to the long axis of the
spine, so they could theoretically spin around on the base and point any
direction. There may be some taphonomic information in either the papers
that describe Tuojiangosaurus and/or Huayangosaurus, but seeing as I don't
speak or read chinese....
<< 3. Has it been shown fairly conclusively that these spines pointed
rearward as well as laterally?>>
<< 4. Going along with #3, are these spines something likely to have
been seriously displaced after death, like flipped in the reverse
direction of their natural orientation?>>
Tough question. The spines were flat based and strictly a dermal bone (ie
not attched via ligaments etc to any other bones) that was sitting in skin
fat and muscle, so theoretically, I could very well imagine them not ending
up where they belonged. Hey, this is why Kentrosaurus' spines were thought
to have been protruding from the hips for 60 years.
<<5. What would be the benefit for *Stegosaurus* to lose these spines?>>
I don't know. Sexier? Lighter? We need a lot more stegosaur remains to even
have a glimpse of a picture of their evolution.
<<6. Could these spines have been for display purposes instead of or in
addition to defense? >>