Re: Pterosaur structure, good job JC

[John Conway <john.a.conway@gmail.com>]

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

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