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Stegosaurian Shoulder Spines



   O.K., this is going out to all the stegosaurian experts on the List:
   1.  What stegosaurians are known to have had shoulder spines?  The
genera I know of are *Huayangosaurus*, *Kentrosaurus*, *Lexovisaurus*,
and *Tuojiangosaurus*.

   2.  What angle do the shoulder spines form with the long axis of the
body when seen in dorsal view, if known?

   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?

   5.  What would be the benefit for *Stegosaurus* to lose these spines?

   6. Could these spines have been for display purposes instead of or in
addition to defense? 

   I can imagine scenarios where rearward, forward, and upward directed
shoulder spines would be advantageous in defense.  With rearward spines,
the stegosaurian could pivot backwards at a theropod attacking the body. 
With forward spines, the stegosaurian could move forwards at a theropod
attacking the head and neck.  With upward spines, the stegosaurian could
crouch down and then straighten up at a theropod attacking the front part
of the body.  All three maneuvers could cause damage to a theropod, if
the spines were used for defense.  In my mind, however, the most logical
direction for defense would be forwards and upwards, pointing towards ten
o'clock in left lateral view, because the stegosaurian could use the
spines to keep a theropod a spine's length away from its neck and head. 
The rear portion of the body would be protected by the thagomizer. 
However, all restorations I've seen of stegosaurians with shoulder spines
show them pointing backwards and upwards, which to me would decrease
their defensive capabilities because the stegosaurian would have to ram
backwards.  It sound more difficult, but I'm not saying it's impossible. 

Thanks in advance-*Thescelosaurus* 

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