Quoting "Thomas R. Holtz, Jr."
<tholtz@geol.umd.edu>:
>> From: owner-DINOSAUR@usc.edu
[mailto:owner-DINOSAUR@usc.edu]On Behalf Of
>> Pedro Andrade
>> What's the functional difference between the
>> ornithischian and the saurischian hip structure,
if any?
> The classic one, though, deals with the
orientation of the pubes. The
> traditional saurischian orientation (pubis
subvertical to
> anterior) is the primitive condition: heck, in
that sense, WE have
> "saurischian" pelves. In ornithischians (except
possibly for
> _Pisanosaurus_) the pubis points backwards. This
would allow an
> increased volume for intestines without having
them expand too much
> laterally, which would in turn allow the digestion
of more plant material.
The other part of this that I've seen is that it
shifts the weight of
the intestines back toward the hip joint, allowing
ornithischians to
increase the size of the gut while remaining bipedal
(for a time,
anyway--given that most of the largest
ornithischians did eventually go
quadrupedal).