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Re: Fixing Feathers



Regarding feather/fish scale homology, Toby White wrote:

<< I suppose I'd just taken it for granted that they were homologous  without 
any special reason to think so.  Is there a special reason to think they are 
not? 
<For one thing, they are composed of different substances.>
Oops.  Right you are.  I was thinking of amniote-type keratinous scales.>>

Not so fast. Fish scales contain keratin don't they? Most every dermal 
structure does. It seems to me that protein, calcium and phosphate get around 
in the body quite generally, and different structures use them as needed. My 
impression is that any creature with teeth will turn out to have a homologous 
structure to scales and to feathers, if you look phylogenetically far enough 
back. Clear proof of this will come when genome workers spot the common 
ancestry among the regulatory genes for the assembly of these structures -- 
give it about ten years, then proof should be in hand, one way or the other.
-- Tom Hopp