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Re: 11th specimen of Archaeopteryx

> On 10/25/2011 7:19 PM, Tim Williams wrote:

Jason Brougham<jaseb@amnh.org>  wrote:

But the crucial point here is that the Kagu (Rhynochetos jubatus) is capable of 
weak powered flight without much climb in altitude.
Thus they retain more of the capabilities of flighted birds than the literature 

As such, the kagu might serve as a poor analog for the evolution of
flight in birds. The muscles that work the wing are reduced, but it
retains full humeral excursion (something that was lacking from the
first birds and their ancestors).

The idea that full humeral excursion might be something that occurred late in the transition to 'full birdiness' would seem (if true) to indicate strongly that the path to powered flight went through an initial passive-energy only phase -- no matter what your preferred path to the basal wing form itself is...

It not hard to imagine that a severely limited powerstroke might be useful enough to an animal that is gliding from point A to point B to expand itself incrementally as optimization occurs -- barring fantastic leaping ability (which is in itself a way to obtain potential energy, same as tree-climbing), the only 'ground-up' scenarios I see for limited upstroke are a little bit 'complicated'.

And really, mostly involve passive energy anyways -- like downhill slopes, dips, etc...