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Re: Pterosaur structure, good job JC
----- Original Message -----
From: "Michael Habib" <firstname.lastname@example.org>
To: "dinosaur mailing list" <email@example.com>
Sent: Friday, January 11, 2008 10:28 AM
Subject: Re: Pterosaur structure, good job JC
Any reason that we should expect neutral positions? I've noted, at least
in some other species, that the slight supination seems to yield a better
wing position given the articulation at the elbow, and the manner in which
the radius fits against the ulna distally.
Mike is correct. And keep in mind that in flight, the shoulder rotates the
elbow rotated slightly to place the elbow near the camberline of the
airfoil, not the chordline.
What do you mean by "in the plane of the wing", in this context? John's
configuration technically has them in the plane of the wing, just palmar
surface forward. While this may seem a bit counterintuitive, pterosaurs
seem to be derived from the typical tetrapod condition.
All pterosaurs that I'm aware of, fly with the palmar surface forward. I
believe that Chris Bennett was the first person to notice this, quite a few
I cannot agree with John's hypotheses on wing folding = extension and
wing deployment = flexion. .......
Chris Bennett independently came to the same conclusion, and detailed it
in his Munich talk (which I''m sure you recall).
If I remember correctly, Chris pointed it out to both John and me, several
years ago. It was obvious at the time that he was right, as he generally is
when it comes to pterosaur bone structure :-) That equates to digital
extension folding the wing and flexion swinging it forward. The same holds
for the other digits. Plus, I've seen a well preserved ornithocheirid wrist
(unpublished) that preserves digits I, II, & III lying approximately
spanwise and flat along the upper surface of the wing in cruise flight
position (I don't remember offhand if that is the position that John uses in
these current illustrations, but the fingers can be correctly placed in
several orientations -- they were an active part of both flight control and
launch; not static protrusions.
I also liked John's earlier version of hind limb configuration during
flight in which the hind limbs were more laterally oriented forming
Those are quite cool, I agree. That position would not be for cruising
flight, though; the limbs would reach that position (if it was used)
during specific maneuevers where aft-support or extra lift was needed.
Stabilization, per se, was probably not too important (as animal flyers
generally use unstable flight).
I'm the one who suggested that orientation to John, as a transient position.
It provides minimum drag when the aerodynamic tail structure is loaded. At
the time, we were trying to get folks to accept that pterosaurs regularly
and transiently use several leg positionings during flight, both symmetric
and asymmetric. We showed that one to make the concept pop out at folks, in
an effort to move folks away from the thought that pterosaurs always used a
single mode of flight. During cruise flight, I'd expect the included angle
between the two ankles and hips to subtend an angle of approximately 127
degrees (the minimum drag configuration for a moderately uploaded tail
complex, supporting only the weight of the hindlimbs so that the hip
musculature doesn't have to actively support them.
To be stabilizing in pitch, the hindlimb/tail structure would need to be
downloaded and pterosaur hip musculature isn't aligned to support
downloading for any significant duration. Downloading would be another
transient, used only when needed and for no longer than needed. Like modern
birds, pterosaurs seem to have evolved away from normally stable flight
A tip of the hat to a great artist and visionary, Hope to see the same
specimen walking one of these days.
I second that!