Re: paleonet PDF PAPER AVAILABLE

[Judith Harris <harrisj@xxxxxxxxxxxx>]

I would like a copy. I am a vert person but this sounds fascinating.

Thanks,

Judith

judith harris
emerita professor
university of colorado museum
p.o. box 278
chama, nm  87520
harrisj@valornet.com


On Sep 21, 2006, at 2:37 AM, Jean Guex wrote:

> 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.
>
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