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Re: Uricotelism

In a message dated 3/3/01 1:57:27 PM Eastern Standard Time, 
patrickmellor@hotmail.com writes:

> How could Postosuchus have sprayed mammal like urine, when all living 
> archosaurs (and most diapsids) are uricotelic? Also, I have a question that 
> think is interesting: If living synapsids (mammals) are not uricotelic but 
> evolved from basal ammniotes along with diapsids, why would they have ever 
> lost something as advantageous in terms of water retention as uricotelism? 

They (we) probably didn't.  Living synapsids, the basalmost living amniotes, 
are non-uricotelic, and our closest living non-amniote relatives, 
lissamphibians, are non-uricotelic as well.  Thus, basal amniotes were likely 
non-uricotelic, and uricotely probably first evolved in reptiles proper.

--Nick P.