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Re: Rhamphorhynchus Perching???



-----Original Message-----
From: Jaime A. Headden <qilongia@yahoo.com>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Cc: fossilsmith@hotmail.com <fossilsmith@hotmail.com>
Date: Monday, August 07, 2000 7:23 PM
Subject: Re: Rhamphorhynchus Perching???


>Allan Smith wrote:
>
><...what would be the most widely accepted pose:
>
>a). balancing on two legs
>b). sitting on it's haunches and gripping the branch
>with it's hands>
>
>  Both would be technically possible. The long tail
>would serve to balance equally a bipedal or
>quadrupedal posture, more so the latter than the
>former due to increased stability. Hoatzin chicks, a
>good analogy in that case, can perch on a single
>branch with their arms lateral to the legs for
>support. The wings in rhamphorhynchoids would probably
>be either up [folded] or backward and out
>[semi-folded] depending on a balance. Remember the
>skull and neck will be very light, and the center of
>balance in these critters in about just posterior to
>the shoulder socket. The short hind-legs in rhamphos
>is long relative to the forearm length (sans humerus
>of the foreLIMB) and this would equalized a
>quadrupedal posture.
>
>  Bipedal posture in some pterosaurs has been
>hypothesized (Unwin, Bennett, and others, references
>and abstracts published over the last couple years)
>but quadrupedal would served better in most taxa
>tested (Bennett et al., 1999, _JVP_ 19(supp. to 3.),
>asbstracts). This may translate into any arboreal
>posture, though I think these critters would have done
>as well hanging squirrel-style from the sides of
>trunks or rock faces. Flying squirrels who could truly
>fly ... ? :)
>
>=====
>Jaime "James" A. Headden
>
>  Dinosaurs are horrible, terrible creatures! Even the
>  fluffy ones, the snuggle-up-at-night-with ones. You think
>  they're fun and sweet, but watch out for that stray tail
>  spike! Down, gaston, down, boy! No, not on top of Momma!
>


I`m not sure pterosaurs could have perched on a branch using their feet
alone.  They didn`t have the locking tendon mechanism, and no reversed
hallux to aid the grasp. I would think they would have climbed about in
cycad branches with both feet and hands. They may have been bipedal on the
ground,........but, I`ve never heard Dave Unwin mention this (quite the
opposite in fact!).