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Re: A physiological query re: feathered theropods



RE: your comments below, David. Much appreciated, but
I was speaking in broad generalizations, and my 35C
was an estimate (my original thought was 30-40C, and
chose a half-way mark to work with). One way to
"test": obtain precise measurements of an entire
feathered theropod specimen, construct an actual
physical model using materials which would come
mathematically close to the weight of the animal's
skeleton, then extrapolate after adding conservative
estimates of the weight of tissue mass (not that
difficult within a specific size range). Then, one
would have, quite literally, a "working model" (Larry
Martin, e.g., has an actual, life-size model of
Archaeopteryx which, in part, provides one with
biomechanical insights). Torpor is an observable
phenomenon among living dinosaurs, and, hence, it is
logical to assume to pre-K/T feathered dinosaurs had
identical, if not similar, thermoregulator mechanisms.
--- David Marjanovic <david.marjanovic@gmx.at> wrote:
> > One can
> > infer that, late at night, with reduced ambient
> > temperature (Ta), and avoiding diurnal
> > theropod/pterosaur hunters, the small feathered
> > dinosaurs (whose body temperature may have been ~
> 35C)
> > could not avoid a lowered MR,
> 
> Depends on several factors. For example, ignoring
> passerines, the body
> temperatures of recent homoiothermic tachymetabolic
> endotherms range between
> 30 and 42 °C or so, resting MRs can differ by an
> order of magnitude IIRC
> (though I think that number includes songbirds). Why
> should any specific
> dino have had, or not have had, 35? Another factor
> should be the
> availability of food, respectively glycogen and fat
> reserves in the body;
> roadrunners live in dry areas with little to eat,
> don't they? The geographic
> variation of ambient temperature is of course
> another problem... and so on.
> Maybe some Mesozoic theropods conformed to your
> model (not improbable IMHO).
> Maybe all. Maybe none. I can't see a way to test.
> Therefore I don't even
> understand why you posted that onlist...
> 
> > and one
> > can assume a period of two hours required to raise
> the
> > core body temperature again.
> 
> Depends of course on what "small" is.
> 


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