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Re: The Roosting Hypothesis



Thanks.

1) GFTR was originally constructed to rebut the claim that trees-down was 
falsified by the perceived lack of arboreal qualities in early-birdish fossils 
-- in particular, the foot.

I flatter myself perhaps, but think it succeeds in that.

:2) the most compelling reason to put the birds-to-be in general -- and the 
specific specimens we talk about -- into trees, is that the trees were there. 

As viable as a GFTR lifestyle is today, it logically "must" have offered even 
more benefits to small bipeds at some point in the Triassic/Jurassic timeframe. 
I base this in part on the idea that foraging in a tree is more difficult than 
simply hiding in one. 

It follows that, pteros notwithstanding, the safety benefits accruing to even 
marginal tree-climbing talents in a largely ground-based animal would have been 
significant -- especially given that it's major predators were also short-armed 
bipeds. And indeed, the pteros may have been crucial to driving morphology 
aiding rapid escape *from* a tree.

3) all the flight-evolving lifestyle ideas I can think of readily -- brooding, 
display, fighting, prey conquest, leaping, maneuvering, even Eric Boehm's 
compelling beachbum ridgesoaring scenario -- all nest nicely inside a  GFTR 
lifestyle ...

But yeah, nothing has been proven.

Congrats on the new gig,  BTW...
--------------------
On Fri, Jul 12, 2013 6:04 PM EDT Mike Habib wrote:

>> 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.
>
>--Mike