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Re: K-T crocodylians



Tom,
    I would think there would have to be an absolute minimum of 5
crocodyliforms surviving K-T (probably more, but not a large number).
    At least one crocodylid, one alligatorid, one thoracosaurid, one
dyrosaurid, plus a baurusuchid and/or a sebecid.  Not sure if any gavialids
go back that far.
    I certainly do not agree with statements I occasionally see that crocs
sailed through the extinction virtually unscathed.  But they certainly seem
to have done better than birds, as one would expect from the combination of
coping mechanisms the crocs had.
                ---Ken
*****************************************

From: TomHopp@aol.com
Reply-To: TomHopp@aol.com
To: dinosaur@usc.edu
Subject: Re: K-T crocodylians
Date: Sun, 22 Jul 2001 11:43:33 EDT

Chris Brochu wrote:

<<My own work shows that most Paleocene crocodylians are very close
relatives
of Late Maastrichtian taxa, and very few major lineages croaked.  In fact,
we
may be looking at metataxa, as some of these Paleocene forms may be direct
descendents of Maastrichtian forms - though as always, we cannot ever
determine whether something is an actual direct descendent of something
else.>>

Yeah, that's the rub, isn't it? Allow me to interpolate a bit from what
you've said: most permissively, we would say that MANY SPECIES survived the
impact, and their direct descendents appeared in the Paleocene record. Less
permissively, we might say that A FEW SPECIES survived and quickly radiated
into MANY SPECIES with strong affinities to Maastrichtian species. Least
premissively, we might say that ONLY ONE SPECIES survived, then underwent
an
extreme rate of speciation to recreate a diversity comparable to that of
the
Cretaceous by the early Paleocene.

I am sure you are reluctant to "pick a number," given the vagaries and
incompleteness of the fossil record, but I would love to hear your best
guess
about the number of direct lines of descent across the K/T event. How about
an "at least this many" figure? Can you give a reference for your/other's
published work bearing on this issue?

Thomas P. Hopp
Author of DINOSAUR WARS, a science fiction novel published by iUniverse
Now Humans are the Endangered Species!  http://members.aol.com/dinosaurwars


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