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Re: ORNITHISCHIANS :-)
In a message dated 6/14/01 3:05:11 AM EST, Mickey_Mortimer11@email.msn.com
<< > Stegosaurs represent a distinct branch of Ornithischia that may or may
> have anything to do with the ankylosaurs. They differ from ankylosaurs in
> practically all aspects of their skeletal anatomy, so if they do share a
> minor similarities these may or may not be meaningful.
This statement doesn't make sense. It doesn't matter how different taxa
are, just what derived characters they share (no matter how minor). >>
What I'm saying is that since so many stegosaurian characters are
autapomorphies, it is quite possible that a few characters here and there
could have evolved independently and coincidentally to resemble characters in
other, distantly related, groups. In other words, the apparently shared
characters could have appeared by long-branch convergence rather than via
common ancestry. If there is long-branch convergence, then the resulting
shared characters are not evidence of common ancestry.
It's fine with me if you hang your hat on the characters that ankylosaurians
and stegosaurians do share and unite the groups as Thyreophora. But I still
regard ornithischian phylogeny at this level as unresolved.