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Re: four winged Archaeopteryx
For my remark about the inability of Archaeopteryx to raise its
forelimb above horizontal, I accepted Phil Senter's analysis. He also
says that Confuciusornis lacked this ability also. Obviously this is
in conflict with Greg Paul's conclusions, and there will have to be
some resolution of that. In my biased view, the other signs that
Archaeopteryx flew weakly or not at all make up a more parsimonious
picture of A as a ground-running displaying feathered little theropod
than any of the alternatives. We shall see.....
Senter, P. 2006. Scapular orientation in theropods and basal birds,
and the origin of flapping flight. Acta Palaeontologica Polonica 51:
The fact that bats and pterosaurs don't use a supracoracoideus system
in their flight doesn't mean that birds can do without it. Bats and
pterosaurs don't have feathers, but that doesn't mean that birds can
fly without feathers. These are different packages of adaptations.
The rigid furcula makes sustained flight difficult, but it doesn't
prevent flight as far as I can imagine. So I concede that one to
David Marjanovic. The flexing of the furcula acts to facilitate
respiratory pumping, so helps to provide the fuel-burning capacity
that powers sustained flight.
My remark about the tail of Archaeopteryx came from Balmford, A. et
al. 1993. Aerodynamics and the evolution of long tails in birds.
Nature 361: 628-631. The bottom line from that paper was that
Archaeopteryx type tails make flight worse, not better. [Therefore I
would argue that that tail was selected less for flight than for
display, or ground maneuvering.]