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Re: Theories on the extinction of dinosaurs



At 11:40 AM 11/16/99 -0600, nicholas roy longrich wrote:
>
>       Not that I have any authority but my gut feeling is that if you
>manage to wipe out every single species of dinosaur, enantiornithine,
>ammonite, pterosaur, mosasaur, etc. down below a level from which they can
>recover, you're dealing with something massive, simultaneous, and
>devastatating,

Not necessarily, as is witnessed by the fact that several other mass
extinctions show little or no evidence of an impact or other single massive
disasters.  The P-T extinction *may* be the only other one with such
evidence, in that case a massive carbon dioxide release.  In at least some
of the other mass extinctions there is good evidence for a more drawn out
process, spread over in excess of a million years.  And even in the P-T
case, there is some suggestion of a longer process, at least arguably.
Thus mass extinctions, including some worse that the K-T extinctions
overall, need not be "instantaneous".  (The K-T extinction was one of the
*smaller* of the Big 5 extinctions).

> and I would expect that neornithines and mammals, far from
>being unscathed, were hit and hit hard.

That I agree with.

> But as Darwin shows with his
>example of a couple elephants breeding enough pachyderms to overrun Africa
>in 500 years, there is an infinitely huge difference between being 100%
>annihilated and only 99.999% annihilated.

In principle a single pair could do so.  In practice such a small
population is usually inviable for various reasons.

--------------
May the peace of God be with you.         sarima@ix.netcom.com