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Re: Patagium attachment Was: Re: Pterosaur.net



On Jan 19, 2010, at 1:21 PM, David Peters wrote:

No semantics game involved. Seriously. And if "evidence supplied in the literature" is going to be used as a "reason" some of that has been falsified in the literature, yet it still resurfaces. Please don't send me back to the literature. I've been there. Send me evidence. Obviously you've thought long and hard about this.

If we're not going to cite evidence in the literature, then what is it there for? The findings of other authors *is* evidence. If you want to go beyond citations and images from the literature, then we can certainly sit down with specimens in any number of museum collections and compare notes. I don't like working from tracings, however.

Just trace one deep wing membrane or one uropatagium and show me why you are correct. If you can't, just admit that you can't.

I don't recall arguing that the wing membrane is deep - I argue that known specimens with preserved wings show narrow membranes - but the attachment appears to be relatively broad, and probably has a hind limb attachment in many, if not most taxa. Already indicated specimens with a broad uropatagium. You mentioned the 2002 study arguing otherwise - no worries there, but I'm not entirely convinced of all the arguments therein. Subsequent papers have argued in favor of the unsplit uropatagium.


On Jan 19, 2010, at 1:12 PM, David Peters wrote:

What is typical about diapsid hip construction? Birds and dinos have an anterior ilium with associated thigh musculature. Crocs and lizards don't. In pteros not only do the anteriorly directed ilia provide for more thigh musculature, they also provide a deeper horizontal stabilizer for flight.

It makes a difference what part of the ilium is anteriorly expanded, because not all portions of the anterior thigh compartment cross the hip to the ilium. The anteriorly expanded ilium in pterosaurs probably expands the iliacus complex, but not anterior compartment proper, so there is unlikely to have been the broad band of muscle going from the tip of the ilium to the knee. If it turns out that there was (which seems to be countered by the soft tissue in the little Anurognathus, but like you said, some bits could be missing), then it would still only be part of the overall compartment, as several of the muscles don't cross the hip at all. Therefore, be careful presuming that an anteriorly expanded ilium means huge thighs - it works that way in birds, but may not be analogous in pterosaurs.

I doubt that the ilia have a stabilization effect on flight, and in fact, pterosaurs were almost certainly unstable flyers like all living powered flying taxa, anyway. If the thighs were broad, and the wing attached near the hip, then there could be a slat effect, but I doubt that was the configuration, based on the current evidence (though John Conway did a nice illustration of how this would work, if it had been the case). You will need to describe how an extended ilium provides flight stabilization.



Are you telling me you see muscles lateral to the anterior ilia? Or not? And did I forget that among the ventral muscles some would be directed toward the prepubes? Maybe that's what you're seeing.

There may be very limited traces of an iliacus complex lateral to the ilia visible in the Anurognathus UV images. Hard to say. Either way, we should expect such a muscle to be there, and in that sense, there would be some muscles lateral to the anterior ilia - but they are running to the proximal femur, not the knee.


Cheers,

--Mike


Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
mhabib@chatham.edu
(443) 280-0181