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Re: four winged Archaeopteryx

The supracoracoideus was experimentally disconnected in pigeons, but they did NOT fly just fine.
This was an experiment done in Nazi-era Germany by Max-Heinz Sy (1936, I believe).

Actually, I think that Jim is referring to the more recent work. Degernes and Feduccia (2001) cut the tendon of the supracoracoideus muscle of pigeons and cockatiels, for example.

They remark that "None of the birds undergoing unilateral or bilateral tenectomy had normal dorsal extension of the affected wing, but each was able to fly well enough to escape if taken outdoors. We concluded that neither unilateral nor bilateral supracoracoideus tenectomy is an effective technique for deflighting cockatiels or pigeons."

I believe that have been some other recent studies with similar results. Note as well that pigeons are something of an extreme case: they are largely burst launching species with a very large supracoracoideus. So they stand to lose the most from such a tenectomy. The same procedure in other species would probably have even less impact.

If a bird or an airplane has to avoid flying in "slower speed ranges", it can't take off.

This turns out not to be the case, actually. Plenty of modern birds must avoid slower speed ranges because they cannot avoid stall at low speeds. They compensate in various ways, a running launch being one. Of course, it is quite unlikely that Archaeopteryx would even need that. I suspect it could hit steady state from a leaping launch (like nearly all modern birds that are semi-terrestrial with low wing loadings). Even if it could not get in especially rapid or powerful strokes, Archaeopteryx would have been able to get far enough to make such short flights of benefit for predator escape. If it had any sort of elevated launch point, then it could get very far indeed, even without any flight stroke at all.

We should also be careful assuming that the deltoids would be as ineffective in an early flying bird as in modern ones. The deltoid is likely somewhat reduced in neornithines because the supracoracoideus has the dominant role in the upstroke (thereby making deltoid elevation largely redundant). In earlier lineages, without an elevation supracora., it stands to reason that the deltoid could be more powerful, so we must not extrapolate too much (as tempting as that can be).