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Re: Bird reduce their "heating bills" in cold climates



Jura <pristichampsus@yahoo.com> wrote:


> There are some good evo-devo reasons to assume that the
> transition scales to feathers was an all, or nothing kind of
> affair (well, scales to filamentous stuff at least). 


I thought that there was good evo-devo evidence that this transition did not 
take place at all.  Instead, work by Prum and Brush indicates that feathers are 
evolutionary novelties, and did *not* evolve from scales.

       "Over the last half of the 20th century, neo-Darwinian approaches
       to the origin of feathers, exemplified by Bock (1965), have
       hypothesized a microevolutionary and functional continuum between
       feathers and a hypothesized antecedent structure (usually an 
       elongate scale). Feathers, however, are hierarchically complex 
       assemblages of numerous evolutionary novelties - the feather 
       follicle, tubular feather germ, feather branched structure, 
       interacting differentiated barbulesâthat have no homolog in any
       antecedent structures (Brush 1993, 1996, 2000; Prum 1999).


References:

Prum, R.O. and Brush, A.H. (2002). The evolutionary origin and diversification 
of feathers.  Quart. Rev. Biol. 77:261-295.

Prum. R.O. (2005) The evolution of feather diversity and function: Exaptation, 
functional redundancy and historical contingency.  In: Briggs, D.E.G. (ed.) 
Evolving Form and Function: Fossils and Development. pp 245-256.