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feathers arising



Sharon Hill asked if feathers, at least early in their evolution might have
been seasonal. Yes, its' possible, but there is no evidence one way or
the other.
 She speculated that "Reptiles shed their skin to grow". Not quite
true. This IS the case for insects and other animals with exoskeletons.
She wondered if this (shedding skin) might somehow be related to the
proposed seasonality of feathers.
 The ANALOGY is that feathers are molted annually, just as reptilian
skin  is. This is NOT growth (in the sense of increased size). I suspect
that feather  moult and reptilian sking molt is analogous, and may be
homologous. Apparently physiologically the mechanisms are very similar.
 But in reality, we have no idea of how feather production evolved. I
suspect that production that involved a follicle, fabrication methods,
and hormonla control are all primitive characters of birds.
  BTW, the growth and regulation of the soft skin isexactly like that
in all the amniotes and consists of alph-keratin.
                       Cheers,
                                Alan

 brush@uconnvm.uconn.edu