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Re: Let's fix those pterosaur hands!
I also agree with Chris on this issue. David: I think you are making
it more complicated than it needs to be. Examination of the
antebrachium and hand indicates, based on several characters, that the
anterior compartment is facing in the cranial direction during
flight. This happens to be the only orientation that makes the
myology and osteology align, as there is no evidence of spiraling
tendons in the distal antebrachium or hand. The fact that this makes
extension movements wider than flexion movements, while perhaps a bit
odd to us, is really of very little consequence, as is the fact that
the forelimb in this pose is no longer "typical", per se, for a
tetrapod. The only osteological shift in this case is that the radius
has moved its position distally somewhat, due to its particular
articulation with the syncarpals. Be careful using the human
antebrachium as a guide - we undergo a substantial upper limb rotation
during development that somewhat reorganizes our upper limb, including
the relative positions of the anterior/posterior compartment borders.
I also would not worry too much about the flight scenarios - we don't
have enough information right now to actually devise the selection
events related to pterosaur flight origins, so I took Chris' scenario
in this case as simply being a speculative experiment demonstrating
that such a path could be imagined. If you have an alternative
scenario that also fulfills the required trajectories, then that
simply fulfills the thought experiment a second time. Personally, I
am not inclined to presuppose any sort of specific scenario for flight
origins in pterosaurs at this time.
Assistant Professor of Biology
Woodland Road, Pittsburgh PA 15232
Buhl Hall, Room 226A
On Sep 29, 2009, at 6:34 AM, David Peters wrote:
Thanks to Mike Habib, I finally got a chance to read Chris Bennett's
paper on pterosaur myology, based on two large pterodactyloids,
Anhanguera and Pteranodon.
Morphological evolution of the wing of pterosaurs:
myology and function Zitteliana B 28 127 - 141
Yes, I have comments, but today they have nothing to do with
myology. It's the architecture, the organization of the skeleton
according to Bennett, that draws criticism....