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RE: Dinosaurs to birds




        -----Original Message-----
        From:   John Bois [SMTP:jbois@umd5.umd.edu]
        Sent:   Thursday, January 21, 1999 9:54 PM
        To:     Dinogeorge@aol.com
        Cc:     Dwight.Stewart@VLSI.com; Alien4240@aol.com; dinosaur@usc.edu
        Subject:        Re: Dinosaurs to birds



        On Thu, 21 Jan 1999 Dinogeorge@aol.com wrote:

        > In a message dated 1/21/99 6:36:24 PM EST, Dwight.Stewart@VLSI.com
writes:
        > 
        > << Or (somewhat alternately): birds were sufficiently derived (in
some way) to
        >  survive the KT extinction.  This is whether a bolide was the
cause or just a
        >  contributor.  Some evolutionary adaptation that was present in
Cretaceous
        >  birds, but not present in Cretaceous non-avian dinosaurs gave
birds an edge
        >  (in this case). >>
        > 
        > Could also have been sheer luck. We have no good handle on bird
diversity
        > during the Cretaceous, but if it was (as I think) quite high, then
most of the
        > birds were killed off, too, and the post-Cretaceous bird radiation
would have
        > stemmed from just a few (say 40-50) survivor lineages (out of,
say, 500-1000).

        Then how do you explain the disappearance of enantiornithines?  More
bad
        luck? 
        @@@@@@@@@@@@@@@@@@@@@@@

           Well, I wouldn't attempt to explain it that way.  :-)  Perhaps,
they (like non-avian dinosaurs) lacked some derived characteristic that
provided at least some birds with "extinction proofing"?  Maybe surviving a
mass extinction event is something as simple as niche flexibility.  I have
asked myself the question somewhat the other way around: what features did
certain birds, crocodiles, turtles, fish, mammals have in common (IF ANY)
that favored them
        for survival of such a massive extinction?  I'm not sure I'm
comfortable with the luck concept when applied to global events.

        Dwight