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In a message dated 8/12/98 5:07:31 AM Eastern Daylight Time,
augwhite@neosoft.com writes:

<< We have to be careful about saying that one "taxon" was "untouched"  while 
 another was destroyed.  In fact, 99.9% of the individuals in both may have 
 been killed, quite unselectively.  By chance or otherwise, one was able to 
 reestablish itself quickly, while the other was not. >>

This is an important point.  The perceived selectivity of the K/T extinctions
may be more a function of the ability of a species to recover from an
environmentally induced population crash than a profile of what lived and what
did not live through the event itself.  The geologic resolution of the K/T
boundary is such that a post-event recovery struggle could stretch out over
dozens of generations and still appear abrupt to us.  This does not remove the
impact as a causative (or contributing) factor for extinctions, but merely
allows that the effect need not be "instantaneous" and provides for further
discussion about what may or may not have contributed to the selectivity of
the event