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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

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.