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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

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