Re: Pterosaur arm supination

[jrc <jrccea@bellsouth.net>]

----- Original Message ----- 
From: "Tim Williams" <twilliams_alpha@hotmail.com>
To: <dinosaur@usc.edu>; <mhabib5@jhmi.edu>; <twilliams_alpha@hotmail.com>
Sent: Sunday, January 13, 2008 7:15 PM
Subject: RE: Pterosaur arm supination


> ..... patagial gliders in which all four limbs were incorporated into the 
> flight surface.
>
> For pterosaurs, this is an open question - as Michael and Jim have been 
> arguing.

Actually, we've been discussing this rather than arguing it.  I don't think 
either of us consider a single scenario to be proven.  I believe Mike leans 
toward all limbs being involved in a single flight surface (acknowledging 
that the properties of that surface vary substantially with location within 
the surface) while I think that all three of the common scenarios may have 
been in use in different species over evolutionary time.  I tend to lean 
toward a disassociation of the tail complex from the wing in the later 
pterosaurs, but there is presently no fossil evidence either way and I don't 
consider it to be proven -- both scenarios are still worth investigating.

>  Thus, it may be unhelpful to treat bipedality and quadrupedality as 
> mutually exclusive.  (These comments are not directed at Michael, BTW.  I 
> haven't disagreed with anything he [or Jim] have written regarding 
> pterosaur evolution or flight thus far,

And though I don't want to speak for Mike, I think this is an area where we 
would agree with you.  I certainly do.
JimC