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Re: Feathers for S excretion



Time to chirp in again...

I like the sulfur hypothesis because it is intriguing, but the more HP Tom Hopp 
speaks, the more it throws the hypothesis into doubt :-)

I don't know if anybody has mentioned this on the list yet, but what about 
mammals??  During the same general time that feathers were evolving mammals 
were evolving.  The first feathered animals (birds/dinosaurs) and the first 
mammals were small, and both likely exploited the insect-eating niche.  Why, 
they, would birds have to evolve these elaborate, sulfur-intwined feathers to 
get rid of excess sulfur while mammals evolved hair?  After all, much of the 
diet may have been the same.  

David (I believe) said that while hair does contain some sulfur (disulfide 
bridges, and such), feathers contain a much higher amount of sulfur.  This begs 
the question: if the first feathered animals and the first mammals were eating 
the same relative amount of sulfur, why did birds evolve these elaborate 
feathers?  Were the kidneys of mammals that much more efficient than those of 
birds?  

This leads me to say that while feathers may be a sulfur dump, sulfur removal 
was not the major reason for their evolution.  

And, what about modern mammals (Insectivora)?  How do they git rid of all of 
this sulfur that they ingest?  Many on this list have said that they kidneys 
are not able to perform this task efficiently.  Then, I ask, how do 
insectivorous animals get rid of this sulfur?  It isn't through feathers.  

Steve

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Steve Brusatte-DINO LAND PALEONTOLOGY
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