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birds scales



Yes, birds do indeed have scales. As a matter of fact they have two kinds
which  can be distinguished on a chicken's foot. One type is, at the molecular
level and in its development, like those of reptiles. The others resemble
reptile scales in morphology, but are quite different at the molecular
level. As a matter of fact the molecules in these scales are like those
in bird claws and the beak. These belong to the same family of protein
molecules that constitute all feathers.
   The proteins in the 'reptile-like scales" are in the same family thatmake th
e soft portion of the skin (in reptiles, birds and mammals) and hair (but there
is no hair on birds or reptiles).
   Specifically, the reticullate (tile like) scales on the ventral (bottom)
side of birds feet are by all test, closely related to the general scales
on reptiles (presumably dinosaurs  as well, but this has never been tested!).
Scales with similar morphology occur on the feet and legs of penguins, but
they are made from the molecules in claws, beaks and avian scales.
   The other type of scales, which are found on the dorals surface, and legs,
 overlap one another. They are called scutes. These scales (in all birds)
 share a series of proteins with beaks and claws. This molecule is closely
related to the family of proteins found in feathers (there are some minor
differences in dwon and contour feathers but it is mostly in the activity of
the family of genes that produce the proteins.
   This group of proteins (refered to a 'feather'-proteins), are unlike the
alpha-proteins that make the skin, hair, mammalian and reptilian scales, in
their primary sequence, genic structure, and the ways in which they interact
to form the filaments that produce the final structure.
  IMHO the reticullate scales of birds represent the reptilian legacy. The
feathers and  related structures in birds are different enough at enough
levels to be considered an evolutionary novelity.
                  Yours for a better integument,
                                      Alan