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RE: Ornithischian vs saurischian hips

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).

Nick Pharris
Department of Linguistics
University of Michigan

"Creativity is the sudden cessation of stupidity."
    --Edwin H. Land