Re: Powered Flight Definition (part of RE: Cost in Aquatic Birds (long))

["Jaime A. Headden" <qilongia@yahoo.com>]

Jim Cunningham (jrccea@bellsouth.n) wrote:

<Are you saying that they could not perform the rotation, or that they
could not 'power' it?>

  That they could not power the rotation. The power flap, as I understand
it, is implicit in the ability of the wing to "scull" or sweep from a
lowered wing, up and forward, back, and down to start, then repeat. This
is different than the up-down or slightly back-forth stroke possible in
more basal shoulders, but the triosseal canal and position of the m.
coracobrachialis permits the humerus to do this both faster, and with more
energy, and the shape and position of the glenoid permits this to occur
over a greater range of motion than possible than in even *Archaeopteryx*,
despite its advanced shoulder compared to -- say -- *Deinonychus*. The
triosseal canal is to increase the moment arm by placing a fulcrum between
origin and insertion. This appears to have been the case in pterosaurs as
well, which developed the "avian" shoulder before birds did. [ha! then
thus it should be the pterosaur shoulder! :)]

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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