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Re: respiratory turbinates



At 03:55 PM 9/12/96 -0500, Dr. Richard Keatinge wrote:

>And I can imagine that turbinates might increase evaporative area and
>therefore heat loss.  But I can't make out how they would help to
>conserve water.  Or am I misunderstanding the above, and also Fastovsky
>and Weishampel's little textbook which seems to say the same thing?  

        I believe that the idea is that the turbinates warm the air on the
way in, which cools the turbinates themselves, then water condenses on them
from the exhaled air, conserving water.  Since endotherms (OK, warm blooded
critters, let's not argue the semantics in this thread, I think we all get
the idea) respirate more, the idea is that they'd dry out faster.
Personally, I think this may be overstated, as water is generated by
respiration, so the increased respiration of a warm-blooded creature may
compensate somewhat.  Obviously, an animal with a water recycling nose is
going to *conserve* water, but I wonder if this is necessary for
warm-bloodedness.
        I wonder if dinosaur's "short nasal passages", cited as evidence for
a lack of RTs, could not have somehow been involved in reducing the surface
area of the airway to avoid losing more water than necessary...
        Yes, this is a very big correlation/causality problem.
Unfortunately, dinosaur metabolics has become such a hot topic that each new
shred of evidence can be tauted in some circles as conclusive proof.  Lord
knows this has happened repeatedly in other segments of dinosaur studies
(eg. bird origins), much to the detriment of both the theories and the
scientists proposing them.  Several workers have pointed out flaws in any
claim of a direct relationship between turbinals and endothermy.  Gregory
Paul had a poster on the subject at SVP '95, but since he is an active
member of the list, I'd rather let him address the subject if he sees fit.

>I guess that any hypotheses about other dinosaurian ways of getting rid
>of heat must remain untestable speculation?  Or can anybody make a
>suggestion?

        I am not sure that the RTs are supposed to necessarily be
heat-shedders. I wonder if perhaps the excess water they would have exhaled
assuming they didn't have respiratory turbinals may have carried away some
of the heat.

        Another interesting point is how do desert reptiles prevent the loss
of heat through respiration.  Considering that there *are* some lepidosaurs
which rely on respiration and prey for most of their water supply, I would
assume that they have come up with some clever way of reducing their
(perhaps smaller) water loss through evaporation.

        Wagner
        (who believes in fast dinosaurs, and is willing to concede
that it is possible that all dinosaurs were warm blooded, which are
not the same point.)
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