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Re: Wilkinson's new pterosaur paper, Cunningham, Habib



Jim C wrote:
I agree about sliding the proximal insertion point. I note in passing that the 
shape of the ilium in lateral view often describes a superb 'form' for an aft 
camberline and that an aft ilium attachment (actually, a full-length ilium 
attachment) might accept the wing membrane loads at a slightly lower stress 
level while allowing the elbow to better modulate the inboard camber.
JimC

>>
Time to remember: Theoretical wing shapes are not real even though they could 
be. 


Mike H. wrote: 

I suspect that it attached near the anterior edge of the ilium in most large 
pterosaurs, and perhaps to the thigh in some others (and perhaps the ankle in a 
few forest-dwelling taxa). I see no reason why multiple attach points cannot 
exist in the same clade. It would simply mean "sliding" the proximal insertion 
point developmentally. Hardly seems impossible, or even improbable.
 
>>
When you say you 'suspect' and 'I see no reason' you're telling us you're 
working on gut instinct and tradition, not evidence. I just sent Mike the 
evidence of seven specimens, all contra the deep-wing paradigm.

>>

Mike H. also wrote:

I'm not sure I understand you. The question, as I see it, is what the inboard 
wing looked like. The outboard wing is obviously a narrow chord structure in 
those species for whom we have impressions, but the inboard wing isn't known 
for certain. Now, I agree with the assertion that most were probably free of 
the hind limb, especially in large-bodied pterosaurs, but that is not at all 
certain.

I don't quite understand what you mean by "wingtip to elbow". The wing has to 
attach somewhere proximally. I suspect that it attached near the anterior edge 
of the ilium in most large pterosaurs, and perhaps to the thigh in some others 
(and perhaps the ankle in a few forest-dwelling taxa). I see no reason why 
multiple attach points cannot exist in the same clade. It would simply mean 
"sliding" the proximal insertion point developmentally. Hardly seems 
impossible, or even improbable.
Cheers, --Mike H.
 
>>
The question is indeed what the inboard wing looked like. And it is certain.
 
I attached (to Mike) seven photo examples of specimens that show what the 
inboard wing looked like in situ. All show the same pattern: narrow at the 
elbow. When such a phylogenetic variety shows the same pattern it's pure 
imagination to concoct any other configuration. Yes, the wing has to attach 
somewhere. It's the same place in all pterosaurs. And it works great!!
 
The Zittel wing is complete, simply ripped off the body. Attach it to a 
complete specimen and see what you get.
 
"re: Wingtip to Elbow: As I discussed in 
 
Peters, D. 2002b. A New Model for the Evolution of the Pterosaur Wing â with 
a twist. - Historical Biology 15: 277â301.
 
The wing membrane needs to be stretched between two points. Otherwise, the 
inner trailing edge is not taut. The wing membrane also needs to disappear when 
folded. Otherwise you've got the saggy diaper look of many poorly restored 
pterosaurs. The examples I attached display no sag in a folded configuration. 
The only way for this to happen, even imaginging the complete absence of soft 
tissue evidence of any sort, would be the narrow-chord model, stretching 
between wingtip and elbow.  
 
You also cannot employ the old myth that the membranes shrank during 
dessication. Doesn't happen with bats. Just doesn't happen. 
 
If you insist on some sort of deep chord behind the elbow, you have to come up 
with a source for this tissue, because it's just not there in the specimens 
attached, and you have to come up with a mechanism for stretching it in a 
direction in which there is no finger or knee or leg to stretch it out. Their 
vectors all go in different directions. 
 
Look closely at any specimen. If you find a configuration different than any of 
the attached, send it to me. I'd be curious to see it. 

David Peters
St. Louis