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Re: Pterosaur structure, good job JC
Dear John and David M.,
re: adductors on the prepubes, well, without modern analogs, there's
just no telling, is there? I would suggest as a hypothesis that since
bones serve as anchors for muscles -- and we first see prepubes on
Sharovipteryx, a creature with hyper-elongated legs and without all
the presacral mass exhibited by pterosaurs -- that prepubes probably
developed to assist that sprawl-legged biped to maintain its
configuration. The logic is: if the prepubes are new, then what is
else nearby is new that it developed in association with? Answer:
elongation of the legs. Perhaps it's not the only explanation, but it
Your reconstructed pteroid is indeed on the medial side of the
preaxial carpal, and I apologize. Seemed to be in the cup. I checked
then realized that the articulating surface is near the cup of the
preaxial carpal and that may be the cause of the confusion.
Here's a solution. It should also be noted that in situ the pteroid
tucks into a vacancy distal to the radiale (Bennett 2007, JVP 27:885)
as it does on Eudimorphodon and all manner of other pterosaurs.
That's because it is not a new bone, but a former centralia. The
migration to the anterior surface can be traced beginning with
Macrocnemus, which, like Cosesaurus, has a poorly ossified carpus
(for whatever reason). The predecessor of Macrocnemus,
Huehuecuetzpalli, likewise has a poorly ossified carpus, so it's
phylogenetic situation over a series of taxa. These migrated carpals,
in my opinion, need to remain in association with the carpus in your
reconstruction. On page 888 of the same issue, Bennett's
reconstruction, like your's, places the preaxial carpal on the
prominence of the distal syncarpal, which acts to separate the
pteroid from the radiale. This situation is remedied by going back to
the insitu specimen on p. 885. You can see that Bennett has labeled
the disarticulated right preaxial carpal (pc) with the sesamoid in
place, but he did not label the articulated left preaxial carpal
still attached to the left distal syncarpal (ds) behind and below.
The in situ specimen maintains all elements in close association and
everything articulates as it should. Adopting this configuration
dramatically closes the gap between the radius and pteroid, as in all
re: the articulation of carpals I-III with the carpus, again on page
885, I'm looking at the insitu specimen and I understand what you're
saying about aligning dorsoventrally. Since this case is different
from that of all other complete and articulated specimens in which I-
III align in the plane of the wing, it may be more parsimonious to
consider the case of AMNH 22555 as one in which the elements have
moved during taphonomy. Clearly there is movement of the right
preaxial carpal and the left metacarpals seem to have followed the
re: the absolutely tiny fingers on AMNH 2255: They appeared to be
rather standard in terms of size to me, similar to those of A.
piscator and other ornithocheirids. If you could, please send me your
photos so I can update my reconstruction.
re: getting into the walking position. I have to ask, do you follow
Wellnhofer's (1991: p. 156) in which the fingers point anteriorly? Or
do you follow Unwin (The Pterosaurs From Deep Time: 201) in which the
elbows are in anterior to the shoulder glenoids? Or Robodactylus (The
Pterosaurs From Deep Time: 207) in which the elbows are in and the
fingers are not included? Or (redrawn from Lockley in The Pterosaurs
from Deep Time: 217) in which the fingers are right for the tracks,
but they do not point anteriorly, as you and Bennett suggest? Or the
one I'll send you in a separate email from my own collection. All are
reconstructions of a walking Anhanguera in different configurations
(Unwin seems to prefer all of them).
re: awkward scenario for muscle attachments. John, I will attempt a
muscle reconstruction, as you suggest. Hopefully it will not be
awkward. I wonder if the problem stems from the problems you and
Chris are having with that Anhanguera skeleton?
re: Compromising on the hind limbs: Don't backslide. You had it right
the first time. Legs out, like Sharovipteryx.
Again, many compliments on your work. If I'm wrong, I need to know.
The most important thing is to get it right.
On Jan 11, 2008, at 10:53 AM, John Conway wrote:
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
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
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
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
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.)