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Re: 11th specimen of Archaeopteryx



Don Ohmes <d_ohmes@yahoo.com> wrote:

> 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...


Yes, there are several lines of evidence that _Archaeopteryx_ was
incapable of sustained, flapping flight.  _Confuciusornis_ too; and
probably _Sapeornis_ as well.  If this is true (and I'm sure not
everyone agrees!) all basal birds might have been gliders.
Nevertheless, it is possible that these gliders might have used simple
flapping motions in order to gain height or added forward momentum
during the glide.


It is true that no modern glider engages in flapping behavior.
However, strictly speaking, no modern glider is "passive", because
while airborne they actively regulate aerodynamic forces by movement
of the glide surface(s) - especially towards the end, to shed velocity
prior to landing.







Cheers

Tim