Re: birds DID NOT evolve from ther[o]pods

["Tim Williams" <tijawi@hotmail.com>]

David Marjanovic wrote:

> > Small theropods leaped from trees and used the predatory
> > stroke to grab prey on the ground.  (Perhaps this explains the more
> elevated
> > glenoid as well?)  The fortuitous lift and thrust components became the
> > foundation for further selection.  This is a "flapping start" model, but
> one
> > which is gravity-assisted.
>
> I see. But how are lift and thrust beneficial in grabbing prey?


Lift and thrust get the predator closer to the prey.  This is also the 
selective force hypothesized in many gravity-opposing ("ground-up") models, 
especially those that picture proavians as dedicated flying-insect-catchers. 
 However, I would aver that the advantage of having gravity with you rather 
than against you in trying to achieve lift and airspeed came *before* 
powered flight, not after.

Initially, the leaping proavian could grab the prey with its hands (their 
primitive function).  But the beauty of small maniraptorans is that they 
were pre-adapted for letting their feet do a lot of the work in killing prey 
(a la that infamous sickle-claw), allowing the forelimbs to become 
increasingly specialized for aerial locomotion.  No more of those damn 
bleeding lizards messing up the wing feathers.

(And before I get accused of "Kippling" :-) , I think this scenario is 
corroborated by fossil and biomechanical data - and draws upon analogies in 
the modern world, birds included.)


Tim

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