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Re: birds scales



>No, a feather is NOT a modified hair.  Mammalian hair was a separate
>development of structures that appeared between reptilian scales.  Feathers
>may (or may not) have been scale derivatives - Alan Brush is the expert here
>- but are NOT homologues to mammalian hairs.  We have no idea, of course, if
>feathers are homologues of pterosaur or Pelecanimimus "hairs".  It may
>simply be that different lines evolved "hairlike" structures as adaptations
>to temperature control (as have bumblebees, for example) and that
>convergence to a hairlike form is common.

I wasn't implying that bird/dino hair was the same as mammal hair.  Since birds
and mammals don't share a common ancestor (unless you go *really* far back), I
wouldn't expect the two to be homologies.  Perhaps I could've clarified that I
was suggesting the hair in question was analogous.

>Also - down may represent a derived, not a primitive, condition.  If
>feathers started out as extended bladelike structures (Alan??) the
>development of a pinnate structure built around a central thickened blade
>may have been the first development (as happens with many featherlike
>structures in nature - palm leaves, for instance).  Forms like down,
>filoplumes etc - even bristles - may be modifications of that structure.
>Just because down looks less structured than a flight feather doesn't mean it
>is more primitive.

Then again, it may mean exactly that.  To go out on a limb (and I think I hear 
it snapping:-), since down is found mostly on chicks, this may show that it is 
a primitive feature (based rather loosely on the principle of neoteny).

Rob

***
"Don't panic!"