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Peter Buchholz wrote:
> All birds are reptiles and all bird young that I know of have feathers.

    Birds are born smooth skinned in the areas that will later 
produce feathers.  We are not just talking about dropping off the 
feathers as the animal gets older, but fundamentally changing the nature 
and texture of the skin.  All modern animals with scales HAD THEM THERE 
FOR THE ENTIE DURATION OF THIER LIFE.  This includes, if I'm not 
mistaken, the scales on birds LEGS.
     In any case, in the case of birds we are talking about a naked 
animal acquiring feathers, not a feathered infant loosing them.       

> you are talking about reptiles in the colloquial "all amniotes that aren't 
> mammals or birds" sense, then you're right; but they do not possess them 
> because they don't have the potential to.  

     What makes you think dinosaurs Tyrannosaurs had the potential to?  
T.rex didn't have a lot of other avian/_Archaeopteryx_ 
osteological characteristics, so why are you assuming that feathers were  
were among the SOFT ANATOMY traits shared with birds? 
     Why do you keep saying that T.rex young were "probably" feathered?  
Infant feathers were offered as a purely speculative possible solution to 
temperature control problems for young dinosaurs. 

> Again, you are using the colloquial reptile.  Birds are reptiles whose young 
> are insulated.  

     But not all reptiles are insulated.  At some point, the transition 
was made from a scaled, non-feathered animal to a feathered one WITHIN 
the Reptilia.  I'm simply saying that with what is known of integument 
development in modern reptiles and birds, the fossil record of skin 
and feather impressions to date suggest that this transition took place in 
one small theropod group.
> The non-speculative reason to assume this is that because at least 
> two branches of the ornithodira have insulative covering, it is more 
> parsimonious to assume that it evolved just once and that all ornithodirans 
> had the potential to be hairy or feathered.

     If the bird feathers and pterosaur hairs are really homologous, I 
admit that would be a problem.  It sure would be nice if we could run 
protein analysis of hairs in a living pterosaur...

LN Jeff