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Re: patterns in extinction, etc.



 > I don't think (and I may be wrong) that there was any significant climactic
 > cooling at the time of the K-T. In fact, I do seem to remember a couple of
 > references who's titles escape me that indicate only a modest if any cool
 > down

Even a modest cooling is still a cooling.

The latest Maastrichtinan climate of Colorado was apparently subtropical
to tropical.  By the Paleocene it appears to have cooled to merely warm
temperate.  Also, the shift to a wetter conditions in the Fort Union may
have been aprtly due to a slight cooling - reducing evaporation.

Not much, but stills a cooling.

 > but certainly still more warmer than todays climate.

Quite so.  Still environmental change will cause population stress,
even if the organisms affected can adapt to the change. Also, other
things being equal, a cooler climate usually has a less diverse ecosystem
than a warmer one.  With fewer species around, a lineage can be
eliminated with fewer actual extinctions.

I was in no way suggesting that *by* *itself* it was a pimary coause
of the extinctions, only that, in concert with all the other things
going on it contributed, perhaps only slightly, to the overall result.

 > In fact the cool spell quickly rebounded to an even hotter climate
 > by the Eocene and was even warmer than the hoyhouse of the
 > Cretaceous!

Oh, absolutely.  But of course by that time the extinctions were long
ever with.

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.