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RE: Ornithischian vs saurischian hips

I suppose the most obvious question to ask next is
what function did the retroverted pubis in
dromaeosaurs serve? 


--- Nick Pharris <npharris@umich.edu> wrote:

> 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).

"I am impressed by the fact that we know less about many modern [reptile] types 
than we do of many fossil groups." - Alfred S. Romer

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