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Re: Thoughts on the new Czerkas book (long)



On Tuesday, September 10, 2002, at 07:17 AM, Thomas R. Holtz, Jr. wrote:

And the biggy: is this thing a flier? I have no problem per se with volant
dromaeosaurs. However, how does one demonstate it? You can't just pick up
the specimen and toss it to see if it flies: if it does, then trilobites
were also volant! ;-) Mere presence of feathers, even large ones on the
arms, might be necessary but not sufficient. My (admittedly quick)
measurements of the best preserved feathers they show (i.e., ones where the
shaft and the edges are both clearly present) finds an asymmetry of only 0.9
at best: they assert these feathers are asymmetrical but do not show
measurements to back up their case. Fully powered flight would require
sufficient mobility at the shoulders, in the arms, etc.: that MIGHT be
possible, especially in basal deinonychosaurs. Still, the case is far from
established, and the use of conditional words like "may" or "possibly" would
actually strenghthen their case.

Feather symmetry is a pretty complicated issue, for one volant birds do have relatively symmetrical remiges and retrices in the inner retrices and secondaries. Outer, and especially leading edge, feathers tend to be where asymmetry is most pronounced. Second there's the measuring question. I'm still baffled as to how anyone can accurately get measurements on the Berlin Specimen of Archaeopteryx considering that the feathers overlap each other, with the leading edge of each vane overlapping the trailing edge of the next (as in modern birds). Other than perhaps the separated tips of a couple of primaries, these measurements just can't be done as far as I can tell. So (not having the book myself) my question is- are these inner or outer feathers, and are they separated or are the vanes overlapping each other?
-nL