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Re: sauropod spines
From: Scott <HORTON@bcrssu.agr.ca>
> I know that sauropods (family Saurischia) are not supposed to be closely
> related to Stegosaurs and Ankylosaurs (family Ornithiscia), but there seems
> to be an uncomfortably large number of convergent evolutionary features in
Well, not entirely convergent. Dermal ossicles are a feature of
many thecodonts - as well as crocodilians. Alterations of the
dermal ossicles to meet the particular needs of each group is not
really too surprising, nor is a slight level of convergence in
the forms taken by the dermal ossicles.
Titanosaurid sauropods actually have dermal *armor*, a little
like ankylosaurs. (Or at least some of them do, such as Saltasaurus).
[P.S. Saurischia and Ornithischia are not *families*, they
are orders, Sauropoda is a a suborder - the families are things
like Titanosauridae and Stegosauridae].
> By the way, can someone explain to me why the family that birds evolved
> is named for a lizard-like hip while the family that birds did not evolve
> is named for a bird-like hip? Convergent evolution again?
*Superficial* convergence. The ornithischian hip looks superficially
like that of birds, but arrives at that appearance in a slightly
Where in birds one bone is *rotated* backwards, the ornithischians
have a backwards growing *spur*.
The peace of God be with you.