Re: dinosaur humps

["Larry Febo" <larryf@capital.net>]

-----Original Message-----
From: T. Mike Keesey <tmk@dinosauricon.com>
To: Larry Febo <larryf@capital.net>
Cc: -Dinosaur Mailing List- <dinosaur@usc.edu>
Date: Friday, March 10, 2000 3:16 PM
Subject: Re: dinosaur humps
>Actually, *no* ornithischian have elongated vertebral spines except for
>hadrosauroids and I think some coronosaurs, both very derived lineages and
>hardly the place to look for features linking ornithischians to other
>groups. Look to more primitive forms such as _Lesothosaurus_,
>heterodontosaurids, _Scutellosaurus_, and _Pisanosaurus_ and see whether
>there are any megalancosaurid features.


OK. Forget about the elongated spines. What keyed me into the idea that
ornithischians may have at one time been arboreal was the mention of the
narrowness of the body from side to side. Seems that was also true of
Megalancosaur.
Of course then there are the ankylosaurs that certainly were not that way.
Then again, they are also highly derived.

 And then there`s the retroverted pubis, that may have been an original
adaptation for getting the center of gravity closer to tree trunks and
branches for more stability. I believe I read this in Romer`s book on vert.
evolution, although the idea was later discounted (no exact reason given as
to why it was rejected,  it seems perfectly reasonable to me).And , of
course, the pelvic girdle of prolacertilians seem much too primitive to make
any comparison with that of ornithischians.

Anyway, you don`t think that early ornithischian ancestors could have been
arboreal?