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Re: dino extinction



From: Nick Longrich <longrich@phoenix.Princeton.EDU>

 >      Now, I can understand severe environmental shifts, but the
 > disappearance of ALL large land herbivores and ALL large land carnivores
 > implies to me something more on the order of environmental holocaust.

Or a series of lesser events that each stressed the animal populations
before they had recovered from the previous event.  Not a knock-out
punch, but rather a rain of punches that accumulate to make a knock-out.

 > New Zealand. New Zealand broke apart from the remains of
 > Gondwana ~80 mya ago bearing a full cargo, and the only things that
 > survived to modern times were ratites, geckos, the tuatara, frogs, etc.
 > Now, what the HELL happened to all the mammals? ... Which makes me
 > think that it's likely that whatever did in the dinosaurs did in
 > New Zealand mammals as well.

That is certainly a possibility.  The fossil record would help here.

However there some things to keep in mind:
        - extinction rates are generally higher the smaller the
          area involved.

        - there was also a substantial mass extinction at the
          end of the Eocene, and there have been many extinctions
          during the Pleistocene/Holocene, which may or may not
          have been anthropogenic.

        - The Maori certainly caused many animals to become extinct
          in New Zealand, and other island peoples have caused at
          least mmost mammals to become extinct on their islands.
          [And I think the Easter Island people drove about everything
           to extinction].


So, we have several more possiblities here, which singly or in
combination may have done in the New Zealand mammals.  Only a close
look at the mammalian fossil record of New Zealand will allow us to
distinguish these causes.  I do not know much about the New Zealand
fossil record, so I cannot tell what it says about this issue. (It
may be too sparse to answer it definitively).

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

The peace of God be with you.