Re: Thoughts on the new Czerkas book (long)

[longrich@alumni.princeton.edu]

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