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

[Fet, Victor]

>>>>>spiders and scorpions didn't suffer a catastrophic reduction in their biodiversity during the K-T extinction.

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

Their Mesozoic record is very limited -- less than a dozen fossil species, of which some indeed belong to modern-"looking" groups (in the same general sense as e.g. turtles) but there are indeed major groups of scorpions which did not survive K-T extinction.

On teh otehr hand, morphological stasis in a very general sense (scorpions, turtles) is accompanied by sweeping evolutionary changes -- the best example in scorpion context is evolution of mammal-specific neurotoxins, obviously Cenozoic! I am sure that turtle specialists can quote some innovations as well.

Victor Fet
Department of Biological Sciences
Marshall University
Huntington, WV 25755-2510 USA
ph. (304) 696-3116, fax (304) 696-3243
http://www.science.marshall.edu/fet/euscorpius/Fet.htm