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Re: The Roosting Hypothesis
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
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 <email@example.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
>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.