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Re: Dino down
My point was that regardless of its "thermocoel of feathers" (sensu
Houck et al.) it still cannot maintain its body temperature. I too
believe that down feathers cannot be sufficient single insulation
because they bog down in wet conditions and cause hypothermia. Down
feathers as single insulators are not advantageous. They were probably
evolved for some other reason (such as keratin excertion and
aerodynamics) and then inherited and turned to advantage in an ectotherm
such as Sinosauropteryx probably was. What advantage would this be?
Well, young penguins (to my inexperienced eye) appear to have down only,
but of course live in a dry climate.
What if, down was developed in dinosaurs as a juvenile characterisitc only,
to provide them with additional thermal protection while in the nest until
such time as activity and body mass passed to a level where body
temperature became self-sustaining?
(it has always puzzled me that if the reason often given to explain the
absence of small dinosaurs is one of a mass/surface area temperature
control; yet we have dinsoaurs hatching from eggs and being below the
"critical size" without any explanation of how they stayed "warm". Hmm they
could have had a higher metabolic rate than adults but I like the idea of
downy baby dinos ! <aaaahh!>)