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Re: Pterosaur structure, good job JC



David Peters wrote:
Dear John and dinolisters,
excellent restoration of pterosaur anatomy is well worth the look. His artwork, I think, places him as the heir apparent to Doug Henderson.

Thanks Dave.

John has envisioned the big traps and lats that so many artists miss. But I notice John does not put adductors on the prepubis.

As David Marjanovic says, should I? (Genuine question.) But then you know, I've probably missed a lot of stuff that isn't forelimb related. The hindlimbs are rather schematic too.


I would like John to comment on his placement of the pteroid in the bowl of the pre-axial carpal, a placement that is not reflected in the fossil record, as recently shown by Chris Bennett.

It isn't! - maybe the picture isn't clear enough to see.

I also note that the radius and ulna are not in the neutral position, but are suppinated. To move the radius to the neutral position requires not more than about a quarter of an inch move distally closer to the medial edge of the ulna and another look at the carpals orientation. With wings extended that places metacarpals I-III in the plane of the wing, as in other tetrapods and basal pterosaurs, not pasted against the leading edge as it appears in John's drawing.

I disagree, obviously. The base of the metacarpals (the articulations of which can be seen on /Anhanguera/ wrists) are aligned nearly dorso-ventrally. I don't think you've fully grasped the position I have the fingers in, it's closer to your position than you may think - I'll try to get some drawings together to make it clearer.


I'm also looking for and having a hard time seeing the big unguals in fingers I-III.

They aren't there. The fingers are absolutely tiny on AMNH 22555, what's there is what I saw of the fossil.


When the wing fingers are placed into the standard tetrapod configuration and the radius is in the neutral position, the fingers face each other during tree trunk climbing and they hyperextend laterally during walking (with elbows oriented posterolaterally), matching ichnites. How can this happen in this configuration without some sort of strange humeral configuration?

I don't see your problem to be honest. All you need do is swing the arms down and bam! walking position, with the fingers aligned with tracks.


I cannot agree with John's hypotheses on wing folding = extension and wing deployment = flexion. I'll await a further explanation that is more parsimonious than the torsioned wing metacarpal hypothesis. Hopefully it will include a phylogenetic demonstration using nonvolant sister taxa of how flexion was prevented and extension became hyper-extension. I also don't understand why palmar flexors can't flex (fold) the torsioned fourth digit.

Ah, well, I think Chris provided a decent scenario for how that might have happened at Flugsaurier. The paths required of the muscles for flight-position to be extension are, well, crazy spiralling. Counter challenge: draw your own scenario of forelimb musculature, I think you'll find it's awkward, to say the least.


I also liked John's earlier version of hind limb configuration during flight in which the hind limbs were more laterally oriented forming horizontal stabilizers. He mentioned examples of wing connection to the thigh or ankle. I'd be very interested in seeing those delineated.

I actually prefer the hip-attachment for pterosaurs like this myself, but variety is the spice of life and all that. I was originally going to to draw this with several different attachment versions, but I decided I'd spent too much time on it already, and went with a 'compromise' position.


A tip of the hat to a great artist and visionary, Hope to see the same specimen walking one of these days.

Cheers Dave, thanks for looking so closely! (... maybe too closely.)


John

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Palaeontography: http://palaeo.jconway.co.uk