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Re: four winged Archaeopteryx

Richard Cowen wrote:

> The fact that bats and pterosaurs don't use a supracoracoideus system
> in their flight doesn't mean that birds can do without it.

No, it doesn't.However, the supracoracoideus has been surgically
disconnected in modern birds (pigeons, I believe), and they continue to
fly just fine after the surgery.  That experiment probably indicates that
birds can fly without it since those surgically altered birds did so.
The reasons they could are fairly obvious.  Removing it just means that
the birds will avoid flying in some slower speed ranges.

> My remark about the tail of Archaeopteryx came from Balmford, A. et
> al. 1993. Aerodynamics and the evolution of long tails in birds.

Irrelevant.  Applies to evolution of long tails in modern birds.  These
birds are doing something quite different with their tails than primitive
long-tailed birds were.  Those primative birds still had a long tail
shaft which had substantial weight.  Their tail feathers were capable of
supporting the weight of the tail through vortex lift, and possibly also
by cascading.

> Nature 361: 628-631. The bottom line from that paper was that
> Archaeopteryx type tails make flight worse, not better.

Not at all.  Archie wasn't a modern bird.  Give him a modern tail and he
most likely wouldn't be able to fly with it.  Give him his own tail back,
and he most likely could.  Flapping calculations indicate that he should
have been a fairly capable flyer.

> [Therefore I
> would argue that that tail was selected less for flight than for
> display, or ground maneuvering.]

There's more than one way to skin a cat.  Why couldn't the tail have been
selected for all three?