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Re: Patagium attachment Was: Re: Pterosaur.net

On Jan 18, 2010, at 11:07 PM, David Peters wrote:

The bracket only predicts split uropatagia in basal pterosaurs if 1) your outgroup is correct (and that is still quite contentious) 2) there are no fossil taxa within the bracket that have a broad uropatagium. As it turns out, even if you decide to argue #1, the bracket fails on #2: several basal taxa appear to preserve a broad uropatagium. Brackets only give the null model, they do not override existing anatomical evidence.

Send one example, please.

Sordes is the obvious one; Jeholopterus seems to preserve a rather broad uropatagium as well. Other examples have also be cited in the literature - see any of the recent reviews regarding pterosaur soft tissue preservation.

In all likelihood, a very broad iliacus ran from the anterior edge of the expanded ilium to the proximal femur, but the other anterior thigh muscles seem not to have run that far anteriorly, so the overall thigh was not terribly deep. This is not actually a surprise, if one looks closely at the particular part of the ilium which is expanded in pterosaurs.

If what you say holds true for Sharovipteryx (whatever it's relationship) it would have had sticks for legs. That would be untenable.

Not necessarily, as the ilia of Sharovipteryx may not be expanded in the same manner as pterosaur ilia - the anterior thigh muscles may be more anteriorly displaced in that animal. In any case, what I am referring to is the typical hip construction for diapsids (actually, most tetrapods), so it's a good place to start. Remember, many muscles in the anterior thigh do not even cross the hip at all.

With regard to "Anurognathus" What you're seeing in the UV images are the ventral muscles attaching to the pubis and ischium. The muscles attaching to the ilium would have been over the ribs, which are exposed, hence, no muscles preserved.

Both the anterior and posterior (i.e. dorsal and ventral) compartments are visible. The ventral musculature associated with hip extension and knee flexion is not running to the anterior pubis - that would be the anterior compartment. The dorsal musculature for the hip and thigh does not run over the ribs. I agree that it would seem that it must given the position of the specimen - this seemingly awkward situation does not occur because that is not how the hindlimb musculature runs in terrestrial vertebrates (also, some of the ribs in Anurognathus are displaced). There are intrinsic back muscles that run from ilium to ribs, however.



Michael Habib
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Chatham University
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