[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Thoughts on the new Czerkas book (long)

Couldn't you base those measurements off of the isolated feather?

Student of Geology
400 E. McConnell Drive #11
Northern Arizona University
Flagstaff, Az. 86001
AIM: TarryAGoat

----- Original Message -----
From: <longrich@alumni.princeton.edu>
To: <dinosaur@usc.edu>
Sent: Thursday, September 12, 2002 1:34 AM
Subject: 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