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




http://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/8/8c/Ctenochasma_elegans.png&imgrefurl=http://commons.wikimedia.org/wiki/File:Ctenochasma_elegans.png&usg=__7GDhp3WU1u9p0TxN9jpjoEewVjA=&h=2040&w=2238&sz=10207&hl=en&start=1&um=1&itbs=1&tbnid=yX67GIU6Q0q1FM:&tbnh=137&tbnw=150&prev=/images%3Fq%3Dctenochasma%2Belegans%26um%3D1%26hl%3Den%26safe%3Doff%26sa%3DN%26tbs%3Disch:1

Or simply http://upload.wikimedia.org/wikipedia/commons/8/8c/Ctenochasma_elegans.png .

 This is an ROM specimen attributed to Ctenochasma elegans, but that's
 dubious and irrelevant. Again, a wee bit of camera shake here.
 Resolution is 2000+ pixels square.

 Here some (not all) of the wing membrane is preserved, either as
 orange colored material or as impressions of a trailing edge that
 continue in its place. The wings are folded. A distal membrane trails
 m4.2 and a continuing line trailing m4.3 is nicely folded in, but
 that's not what we're looking for.

The orange patch is a patch with irregular edges; look at its distal end, which is caudal to the left ulna, which absolutely can't be where the edge of the wing membrane was in life.

I wonder if it tracks an outflow of some decaying liquid from the torso. If so, it has nothing to do with the wing at all.

 Evidence on the other (dorsal to the torso) femur is weaker. The
 color of the matrix simply dulls sharply at the predicted attachment
 point.

Nothing does anything sharply in this blurry photo.

What I see is that the iron oxide thins out. It does so all around the fossil (in a wide perimeter), as well as on both sides of the big crack with the dendrites. That's where iron(III)-breathing bacteria came in, ate organic matter, and changed the reddish iron(III) into greenish iron(II).

 Evidence for any other sort of wing attachment is weaker still.

Not merely "weaker" -- this specimen doesn't preserve any evidence against any wing attachment at all.

 David Hone provides the Vienna specimen (with narrowing at the elbow
 and a distinct line to the femur) here:


http://archosaurmusings.wordpress.com/2009/04/13/where-is-the-pterosaurian-5th-finger/

Fine...

 As  a side note that the propatagium attaches to the deltopectoral
 crest, not the neck!

I can't see the limit of the propatagium. All I can see is an irregular arrangement of dendrites (both manganese(IV) oxide and iron(III) oxide ones) that continues all the way to the first 3 fingers, around them, and to the base of phalanx IV-1. I can't see a smooth, continuous line, nor the lighter color that the brachiopatagium has.

And even if, in the region of the propatagium, the dendrites do indicate the limit of the propatagium, why do you extrapolate the curve through the place where the deltopectoral crest was prepared out? Are you sure the curvature didn't change in there? I don't have an opinion on where the propatagium was attached, I'm just saying this photo of this specimen doesn't tell us.

 From such clues we build a case. Some are better clues. Some are
 weaker.

The ones you're giving can't be distinguished from pareidolia.

============

BTW, people, there's no need to send me everything twice. I get every DML e-mail into my inbox and read it; I don't need an extra personal copy. At present, there's a lot of free space in my inbox, but getting a lot of mail and then having to delete half of it afterwards is a bit annoying. It was especially so when my (then smaller) mailbox was almost full.