RE: mammals morphologically evoluated a lot since the Ceno zoïcum, invertebrates did not.Why?

[Ken Kinman]

On Tue, 7 Feb 2006 11:30:19 -0500, Fet, Victor <fet at MARSHALL.EDU> wrote:

For scorpions, it is always taken for granted but might not be true....

there are indeed major groups of scorpions which did not survive K-T extinction....

 the best example in scorpion context is evolution of mammal-specific neurotoxins, obviously Cenozoic!
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Hi Victor,
     I would certainly agree that many major scorpion groups died out *before* the K-T extinction (most well before the Cretaceous even began).  I suppose some families of scorpions could have gone extinct the end of the Cretaceous, but with so few fossils (mostly from the Middle Cretaceous?), how would you know that the end-Cretaceous extinction did them in?  Whatever scorpion families existed at the end of the Cretaceous, I still suspect a majority of them survived (although with fewer genera than before the extinction).  Not a *catastrophic* extinction like that which wiped out the vast majority of families of birds at the end of the Cretaceous.  Birds just barely made it through.
  ---Cheers,
           Ken Kinman
P.S.  Are mammal-specific neurotoxins of scorpions effective against certain clades of mammals, or against mammals in general?  If the latter, then such toxins could have easily developed during the very long Mesozoic history of mammals.