paleonet PDF PAPER AVAILABLE

[Jean Guex <Jean.Guex@xxxxxxx>]

To anyone interested I can send the following paper in PDF form:

"Reinitialization of evolutionary clocks during sublethal 
environmental stress in some invertebrates."

Abstract
This paper describes the influence of high environmental stress on 
evolutionary trends in some selected Mesozoic ammonite lineages and 
some protists. During extinction periods, many ammonoids are affected 
by drastic simplifications of their shell geometry, ornamentation and 
suture line. We observe that relatively tightly coiled ammonites can 
give rise to highly evolute forms or uncoiled heteromorphs with 
simple ornamentation and almost ceratitic suture line - a phenomenon 
called "proteromorphosis". Such simplifications often correspond to a 
reappearance of ancestral geometries (primitive ornamentation, 
evolute coiling or uncoiling) which suggest that the evolutionary 
clock of these organisms can be reinitialized by extreme, sublethal, 
environmental stress such as giant volcanism (including its 
consequences on diverse pollutions and on climatic changes) and major 
regressive events.