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Re: Senter 2006, Confuciusornis, and humeral mobility

>1) the recovery stroke is limited such
> that it is difficult to get the wing out of circulation in time to avoid a
> negative lift coefficient and

That brings to mind one more big difference between Confuciusornis and any
modern bird. The primaries are distributed along a second finger which is
robust and retains mobile joints. Unlike any living bird, therefore, the
distal primaries can be folded relative to the proximal ones. Wouldn't
flexion of the wing finger, folding the primaries up before the upstroke
begins, help reduce negative lift? It does in bats, right? And wouldn't
such a snap of the wing finger at some point on the power stroke,
accelerating the distal primaries to very high speeds, significantly
increase lift?

>2) there is insufficient excursion on the
> shortened downstroke to build up to full circulation by the midpoint in
> the stroke where the primary force production occurs.

Can you say this with confidence without doing any calculations or
modeling at all? I fear we may be in danger of making a priori qualitative
assumptions when the answer may be quantitative. In other words, an animal
with limited dorsal mobility of the humerus may have LESS ability to
generate lift than, say, a pigeon, but it may still have ENOUGH lift for
powered flight.

Picture how many different flight strokes could be possible if you add two
points of wing flexion - at the first and second finger joints. The
resulting complexity seems daunting to me, at least. I have read that
bats, which can do this, often fly with different configurations of the
left and right hand during each wingbeat: