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Re: four winged Archaeopteryx
Are there any modern flightless birds with fully developed flight
feathers??
Frank (Rooster) Bliss
MS Biostratigraphy
Weston, Wyoming
www.cattleranch.org
On Sep 23, 2006, at 2:35 PM, Tim Williams wrote:
Richard Cowen wrote:
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.
This is throwing the baby out with the bathwater. I think we can
say with a high degree of confidence that _Archaeopteryx_ was not a
superb flier; but to say that it was a completely ground-dwelling
theropod with the remiges and rectrices used solely for display is
going *way* too far, IMHO.
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.
Ummm.... no. Baldwin et al. (1993) were looking at tail elongation
in *modern* species species, and examining its effects on
aerodynamics. No modern bird has an "_Archaeopteryx_-type tail",
just as no modern bird has an _Archaeopteryx_-like body plan. It
is not helpful to extrapolate tail length in modern birds to tail
length in _Archaeopteryx_, given that the flight mechanics of early
birds were very different to modern birds. The long tail and
"rectricial frond" of _Archaeopteryx_ may have served a purpose in
aerial locomotion, in a manner that has no modern analog. These
issues have been discussed at length in papers by Gatesy, Dial,
Hutchinson, etc.
[Therefore I would argue that that tail was selected less for
flight than for display, or ground maneuvering.]
As well as _Archaeopteryx_, a long tail is also seen in other
Mesozoic birds (e.g., _Rahonavis_, _Jeholornis_/_Shenzhouraptor,
_Yandangornis_, _Dalianraptor_). Some of these birds show improved
flight capabilities compared to _Archaeopteryx_, suggesting that a
long tail is not an impediment to flight. One view is that the
long bony tail was integral to an early experimentation in flight
where the tail played a greater role than in modern birds.
Cheers
Tim