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RE: The Roosting Hypothesis

From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu] on behalf of Tim Williams 
Sent: Sunday, July 14, 2013 2:51 AM
To: dinosaur@usc.edu
Subject: Re: The Roosting Hypothesis

Lost in truncation.  Mike's response encapsulates my own opinion exactly.

> From:  don ohmes <d_ohmes@yahoo.com>
> Summing -- it follows that a trees-down path to powered flight *can*
> occur
> in the absence of a reversed hallux or "arboreal adaptations".
> GSP's claims re curvature will do much to define future discussions if
> they hold up -- given the presence of sharp claws on even one fossil,
>  I am
> optimistic...

I like the GFTR hypothesis, as Don calls it, from a thought experiment
standpoint.  It seems to be both plausible and consistent with known
biology.  However, to the extent that it holds true, the same list of
observations basically confirms that we can't tell if there was
"trees-down" component to flight origins (just as we cannot refute it).
GFTR seems to predict, essentially, that the animals would look
terrestrial.  The claw curvature measure might give some indication of
more climbing, but it's not a silver bullet.  So, ultimately, we have
three models: high arboreality, partial arboreality, and full
terrestrially for flight origins.  The high arboreality predictions do
not seem to hold true, so we can tentatively discard that one.  But then
there seems no way to test between the other two, as they predict the
same morphology.  Since there was never a particularly compelling reason
to put these animals in the trees vs the ground to begin with, I would
call the result a stalemate.