Re: Origin of feathers

["Norton, Patrick" <Patrick.Norton@state.me.us>]

>But if you state that pre-feathers appeared >for< insulation, you imply   
that homeothermy was already present >before< the pre-feathers appeared.   
(Otherwise, what would they be insulating?) <

An insulator will keep heat out just as effectively as it will keep heat   
in.  What Regal suggested ["The evolutionary origins of feathers." 1975.   
Q. Rev. Biol. 50:35-66] was that the evolution of feathers began in   
facultative homeotherms with the elongation of scales that reduced heat   
flow to the body (a form of insulation) by providing shade. Once   
obligatory homeothermy developed, that feather would would function   
equally well in reducing heat flow from the body.

>I don't think we know enough about homeothermy to say anything coherent   
about how it may have developed in birds and archosaurs.<

I'm not speculating on the evolution of homeothermy. But to speculate   
just a bit on the topic of this thread----I believe that the origin of   
feathers will eventually be found to have a thermoregulatory explanation,   
not aerodynamic.  I also believe that the vertebrate record will   
eventually document at least two roads to flight; one that included a   
tree (or cliff) dwelling phase and one that did not.  The first led to   
the quadrupedal non-cursorial bats and pterosaurs, and the second to   
birds.