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Re: Running with arms out



>Date: Sun, 9 May 1999 15:15:01 +0100
>From: "John V Jackson" <jjackson@interalpha.co.uk>
>To: <dinosaur@usc.edu>
>Subject: Running with arms out
>Message-ID: <003701be9a41$b45e8e40$1be11ac3@default>


(Snip)


>Is a gradual lengthening of arms really there?  (This is a delicate point
>because in any theory there has to be a lengthening of the arms, but
Larry's
>(and my, Larry!) position  advocates an explosive initial lengthening for
>flight purposes; however, there might also be a lengthening for
>tree-climbing purposes.  In this case, we might expect any lengthening to
be
>associated more with the smaller specimens, as is I believe the trend.)

I don`t advocate an "explosive initial lengthening" in proto-birds. My view
is that flight developed in the trees, with a gliding phase utilizing a wing
"membrane" and a gradual development of true flight from there. I believe
that Pterosaurs went through this phase, and also did not develop from the
ground up.  My particular view has it that Pterosaurs were an intermediate
stage to birds. They already had the membrane, and were already true fliers.
My thoughts are that feathers developed first as insulation, then became
aerodynamically shaped (so as not to cause drag and interfere with flight)
and gradually replaced the flight membrane in a species that became more
cold adapted in either more polar latitudes, or higher altitudes, and at
some point lost the long wing digit and became "birds", which in turn
periodically gave rise to secondarily flightless Theropods.

Go to my web site to see what I think ......http://www.capital.net/~larryf/