Re: Nice example of narrow chord pterosaur wing on the 'net

[David Peters <davidpeters@att.net>]

On Mar 20, 2010, at 12:03 PM, Mike Habib wrote:

>> Well, to my eyes it looks like it went beneath the surface of the matrix 
>> originally and was prepped away. Or they didn't go deep enough (less 
>> likely). Here one simply takes the >trajectory< of what data you do have and 
>> continue it in the same curve, which runs right about at the edge of the 
>> prepping (sad) until the prepping ends and -- voilá!
> 
> What is your support that this us an accuate technique for reconstruction?

I have described no technique here. And no reconstruction. This is pure 
observation. 

> There are many reasons why this could be misleading.

The term "many reasons" is way too open ended. Put your cards on the table. Be 
specific. 

> 
>> --there is a line of something leading to a point 2/3 down the femur, 
>> exactly as shown in the Vienna specimen
> 
> Actually, if you continue the curve using a spline, instead if drawing a 
> straight tangent line, then you get an attachment somewhere in the tibia.

Are you sure you don't get a death spiral? Please, Mike, You can avoid it only 
for so long... Let's talk about that line leading off the tibia. And identical 
lines on the Vienna specimen. And, if you put the body back on the Zittel wing 
(see Peters 2002) another identical situation. I'm not the only one doing this. 
John Conway duplicates this here:

http://2.bp.blogspot.com/_VgcbfiMgVJA/S2hR_7lcyxI/AAAAAAAAAIQ/O3CQ0ZAf6rM/s1600-h/Pteranodon+longiceps-735463.png

and here:

http://palaeo.jconway.co.uk/dissecting_rhamphorhynchus.php

> But I don't think you can make either argument. The membrane isn't there, so 
> making wild suppositions is no good here.

"The membrane" was described by Wellnhofer in 1970. I'm not the first to see 
it. Or are you talking about a membrane attaching to the tibia, no wait -- the 
fifth toe - that isn't there? 
Please be specific or send drawings. You are adding to the confusion. We need 
your finger to point to somewhere on the picture somehow.
> 
>> 2. to MH: Okay, well, Pittsburgh SVP is coming. Let's put this specimen on 
>> our list. And let's check out that anterior thigh together.
> 
> I'm in Pittsburgh already. Happy to show you the critter. It is nice but does 
> not demonstrate wing extent.

See above. "Does" -"does not" are closing arguments. We haven't gotten there 
yet. Time to provide the charts and graphs.
>> 
> 
>> Summary: I add this to my list of narrow-chord wing membrane examples (some 
>> good, some not so good). And I remain eager to see a single example from the 
>> opposing camp.
> 
> The opposing camp has given several examples.

Wrong. NONE have been delivered. You have only >cited< examples. 

> You have dismissed them for various reasons, and while some of your arguments 
> bear merit, others can say much the same about your narrow wing examples, 
> leaving us eagerly awaiting a clear example of either one.

If you don't like this wing example show what >is< happening in the fossil.

> Personally, I find several of the hindlimb attachment examples robust,

Send  just one  of your best.

> but even then, we do not have attachments for the vast majority of clades, 
> and attachment could easily vary.

If there was an alpha example and an omega example I would agree that we could 
have everything inbetween. But we have only one example over and over. 
Seriously, send one opposing example and I will be on your side. 

> Fortunately, we have lots of good outboard wings, so we can reconstruct that 
> much with relative confidence. It turns out that the specifics of the inboard 
> wing don't make much of a difference when you work out the numbers, because a 
> fillet is not very aerodynamically active.

Irrelevant at this point.

Ciao,

David


> 
> Cheers,
> 
> --Mike H.