Re: dinosaur humps

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Fri, 10 Mar 2000, Larry Febo wrote:

> >> I find it interesting in comparison to look at Megalancosaurus (check
> >> out Dave Peter`s website at:
> >> http://home.stlnet.com/~azero/Megalancosaurid.html ). It has tall
> >> neural spines, and it`s feet seem well adapted for grasping narrow
> >> branches. I can`t shake the thought that perhaps Ornithishians had
> >> evolved from this type of Prolacertiform.
> >
> >Unfortunately for your hypothesis, primitive ornithischians did not have
> >tall neural spines:
> 
> True,....but neither did most prolacertilians. Perhaps it was just an early
> expression of certain genes due to enviornmental conditions.

A gene found throughout Tetrapoda, perhaps...

> If not heat regulation, then perhaps an early form of protection of
> the spinal column from bites of predators.Perhaps some ornithischians
> were faster and more agile than others, and didn`t need this type of
> protection, hence it`s loss by evolutionary process, and the three you
> mention just happen to be of the latter type?? (maybe?)

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.

You might as well propose that spinosaurs are descended from crocodylians
by virtue of their unserrated teeth ...

-- T. Michael Keesey .................................. <tmk@dinosauricon.com>
   My Worlds (including The Dinosauricon) ... <http://dinosauricon.com/keesey>
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