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EXTINCTION & Breakup



Just a hopefully quick note. Actually, I never asked for closure of the
debate, it is too interesting not to discuss as more and more evidence
comes up. I just wanted the passions related to specific hypotheses not
to get out of hand and generate unwarranted personal attacks or snide
comments, etc. I think passion for the wonderfulness of paleontology
is great - if I didn't have it I would be out earning real money doing
something far less interesting and, in my current opinion, significant.
If passion gets side-tracked toward specific hypotheses, then trouble
can follow as contra evidence is not given a sufficient hearing and
the hypotheses become less rigorous as a result. I want others to really
do their best at providing contra evidence to anything I support because
if it can't hold up, I want to move on to something that does. I just want
to get closer to the answers. Consequently, I want to hear the arguments
of everyone here but just want to hear them framed in a way to produce a
constructuve dialectic rather than a barroom brawl or school yard.

  Now as to the breakup of Pangaea. If vicariant and similar mechanisms
have any validity at all - and I think they do as part of a complex
whole rather than as a single answer for biogeographic patterns as some
researchers do - then you would expect the breakup to have a complex effect
that would also tend to provide isolating mechanisms for large populations
and, consequently, provide a stimulus for an increase in diversity rather
than a decrease. Now this may be countered in the long run by changing
climatic conditions in some regions, but that's a much slower process,
I think. Further, breakup during regressive stands should provide a more
reasonable climate in areas that would previously have been in the middle
of the gihugrongous (=Huge - always wanted to try typing that word)
continent, as paleoclimate types have always suggested that climate
extremes would be characteristic of the big Pangaea mid-continent
during non transgressive times. Just my 2 cents worth

Ralph E. Chapman, Applied Morphometrics Laboratory (The Shapes of Things)
National Museum of Natural History, Smithsonian Institution
MNHAD002@SIVM.SI.EDU