Re: query about extinction

[Phillip Bigelow <n8010095@henson.cc.wwu.edu>]

 Vicki Rosenzweig expounded:
:> > I was wondering what the largest land animal known to
:> > have survived the K-T extinction was. (I have a hunch,

Sean retorted:
>Or are crocs a special case?

This doesn't directly address Vickie and Sean's comments, but I thought it
would be a good place to quote from an authority on the subject.  The following
excerpts are taken from Laurie J. Bryant's monograph, "Non-dinosaurian lower
vertebrates across the Cretaceous-Tertiary Boundary in Northeastern Montana"
[University of California Publications Geological Sciences vol. 134, year
1989, 107 p.]
             Begin Quote
"The 74 non-dinosaurian lower vertebrate taxa from the study area include
elasmobranchs [sharks], osteichthyans [bony fishes], amphibians, reptiles
and birds.  The Hell Creek Formation is characterized by elasmobranchs,
archaic fishes, numerous lizards, the most diverse known turtle fauna, and
at least five crocodylids."

"Many fishes (particularly sharks), many lizards,and two uncommon crocodiles are
unknown in the Tullock Formation [the time after the extinction] in the
study area.  Yet some fishes (such as gars), most salamanders, most turtles,
and the three common alligators were little affected by terminal Cretaceous
events. Champsosaurs [funny-looking crocodile-like archosaurs with pointed
snouts] appear to have become larger and more numerous in the study area
after the end of the Cretaceous.  Most of the taxa that apparently went
extinct were extremely rare in the Hell Creek Formation."
               End of Quote 

  One interpretation of Dr. Bryant's results is that relative *abundance* of a
particular species was the key factor in determining whether it lives or
dies.  That doesn't mean that size of the animal, or that metabolism
weren't factors, too.
The "rareness" factor makes a lot of sense.  If we could wave a magic wand
and cause 80% of the total population of *each* species to die, guess which
ones would be able to recover after the die-off?  The most abundant.
 Since there are 4-5 billion of us running around, our species would be
healthy after 80% of us are gone (we may actually be better off ecologically). 
If we removed 80% of the remaining snow leopards, whooping cranes or giant
pandas, there may not be enough left to form a sustainable breeding
population.
  Of course, all of the above only relates to non-dinosaurs.  Depending on
who you talk to, at the K/T boundary, non-avian dinosaurs were either: 1) very
abundant; 2) extremely rare; or 3) already extinct.  Now THAT'S narrowing
the options down!  Isn't science wonderful?