re: Burgess Shale

[@uga.cc.uga.edu:Schwimm@USCN.BITNET (Paleontology Columbus College, Georgia)]

I agree with the first respondant that Gould's concept of disparity in the Middl
N is excessive--I think grossly so.  To some degree, this seems to be a reflecti
 general view and paradigm that all nature is chaotic
and that wild excesses characterize nature (i.e., wanton waste of failed
taxa in the early diversification of sclerotized metazoans).  The recent
paper in Science (cited below) argues that there was actually an
explosive diversification in the early Cambrian well below Burgess Shale
time, and by extension, things should have quieted down by then.
   Another factor is that the Cambrian keeps shrinking: we are currently
told the base is now dated ca. 550 Ma and potentially shrinking to as
young as 538: this is about the age we estimated for the Middle Cambrian
when I was in grad school.  The shrinking duration of the Cambrian implies mo
more rapid events in general, and tends to make all events seem more
"explosive">[D."

see: Bowring,S. A. and others, "calibrating rates of Early Cambrian
      evolution"  Science, 261:1293-1298, 3 Sept. 1993.

                   David Schwimmer
               Dept Chem. & Geol.
                 Columbus College
                   Columbus GA 31907-5645>[A>[A>[Aschwimm@USCN.CC.UGA.EDU>[B>[B>