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Re: flying Archie

At 11:01 AM -0700 9/24/06, T. Michael Keesey wrote:
>> This could have been one selective pressure that kept _Archaeopteryx_ in its
>> plesiomorphic coleurosaurian body plan.
>Why does selective pressure need to be invoked? This is the earliest
>known winged theropod, and it's probably not too far removed,
>chronologically, from the very first ones. Long tails are just the
>ancestral state--perhaps there had not been enough time to "evolve out
>of them".

Remember that feathered Solnhofen fossils show little variation; all 10 known 
fossils are usually assigned to Archaepteryx, although there has been some 
splitting from time to time. There's a lot more variation in the Yixian fauna. 
That is consistent with Archaepteryx being much closer to the origin of birds. 

We might learn something interesting about the origins of flight by looking 
systematically at the variability of traits among Archaeopteryx.

Jeff Hecht, science & technology writer
jeff@jeffhecht.com  http://www.jhecht.net
525 Auburn St., Auburndale, MA 02466 USA
v. 617-965-3834; fax 617-332-4760