Re: Patagium attachment Was: Re: Pterosaur.net

[Mike Habib <habib@jhmi.edu>]

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