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Re: the start

 > How the early Dinosaurs took over was a combination of good luck and
 > improvements in the hips (erect stance). The good luck came in the
 > of ... here we go again ... an impact during the Triassic/Jurassic.
 > During that impact the world was devastated and the dinosaurs and
 > other archosaurians, although greatly reduced in number, were able
 > quickly seize most of the land niches.

While it is true that the Norian extinctions probably did have alot
to do with the success of the dinosaurs, I am truly skeptical
that an impact was involved at all in those extinctions.  The
only source I know of that cites it is Greg Paul in "Predatory
Dinosaurs".  The more recent, and more carefully reviewed, articles
I have seen fail to mention any evidence for an impact correlated
with the Late Triassic extinctions.  And one, at least, of these
references would probably have mentioned it, as it included a
table of correlates with the various major and minor extinctions
of the Mesozoic - including impact evidences.  It makes no mention
of *anything* like that for the Late Triassic extinctions.

What is the evidence for this impact, and for its *relevance*
to the Norian extinctions?  Where can I find a peer reviewed
article discussing it?

Also, in the recovery from the Norian extinctions the dinosaurs
had some competitors - especially the advanced pseudosuchians
like Poposaurus which shared many of the advantages of dinosaurs,
such as an improved, erect, stance, and had the same archosaurian
heritage as the dinosaurs.  I think an interesting question might
be why the dinosaurs beat out the pseudosuchians.

swf@elsegundoca.ncr.com         sarima@netcom.com

The peace of God be with you.