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Re: Feathers for S excretion (very long)

Larry wrote:

> But,.....if the protobird lived in an arboreal enviornment, and was
developing protofeathers for insulation, this would indicate a non-tropical
enviorn, with only occasional rainfall.<

A stretch, at best. Insulation keeps heat out as well as it keeps heat in.
An insulative integument such as protfeathers would, for the most part, be
equally adaptive for an endothermic animal (particularly a small one) living
in either a warm or cold environment.  One could easily construct a scenario
whereby protofeathers might provide an adaptive thermoregulatory advantage
for pre-avians living in hot, treeless, arid environments (such as the early
Cretaceous Gobi?).

>  Seems to present itself as a good arguement >>for<< the trees-down

I don't reject ground-up, or trees-down, or even trees-up for that matter,
but I don't think what you've offered is a good argument for any of them,