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Tim Williams wrote:

> Here it comes down to at what stage the wing started to become a
> lift-generator.

Since even a flat plank is a pretty good lift generator up to a lift coefficient
of about 0.9, it probably happened early on.

> However, even
> if lift was not the primordial purpose of the proto-wing, the proto-wing may
> still have served an aerodynamic / aerial locomotive purpose, e.g.:
> aerodynamic thrust --> aerodynamic lift (Burgers and Chiappe, 1999)
> aerodynamic drag --> aerodynamic lift (Garner et al., 1999).

I tend to prefer a scenario where aerodynamic lift --> aerodynamic liftand
aerodynamic thrust --> aerodynamic thrust, but that's just me.

Re most of the scenarios leading to flight -- for the most part, they are not
mutually exclusive.

> >Also, using the low aspect ratio tail to develop sufficient lift
> >(upload) to offset the weight of the tail plus most of the weight of the
> >hindlimbs will provide yaw stability while also providing an effective tail
> >download that will enhance longitudinal stability  [snip] I'd
> >expect the animal to be moving in the direction of decreased stability
> >almost
> >from day one.
> Hmmm...  that is an interesting idea.

Several species appear to have used it.  As an aside, most flying creatures
including airplanes tend to fly the tail at about half the lift coefficient of
the wings, whether generating a tail download or an upload.  The last thing one
wants to do is stall the tail while the wings are still unstalled.