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Re: Query on RT function



54 mg / liter sounds like saturation at a bird's core temperature.  Bird
lungs have to stay warm and wet, and they need to get pretty intimate
with the air.  Without a nasal system, every liter that left the bird
would carry 54 mg of water.  If the nasal passages reduce this to 17,
they have saved the difference.  

Whether the 54 mg originally came from the nasal passages or the lungs
is immaterial to the savings.  That's because the lungs would have
dumped the moisture into the air if the nasal passages hadn't done so
first.

The nasal system dumps heat and moisture into inhaled air, but most of
it has been stolen from the exhaled air.  That means efficiency.  It
also protects the lungs.

A good RT system would be especially important for the tiny endotherms
from which I understand all mammals involved.  Tiny mammals breathe the
fastest, and they have the least heat and water to spare.  

I don't know if dinos had RTs, but if they were endotherms with less
thrifty respiratory systems than those of mammals, the waste of water
and heat could have prevented dinos from getting as small as mice, for
example.

- Stephen Throop