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Re: CNN:Is it snowing in Oregon: a question...



At 12:10 PM 1/22/99 PST, Kevin Hedgpeth wrote:

>>So, what they are suggesting is a highly active, very aerobic 
>ectotherm.  (I
>>suppose if it were big enough it would even be a highly active, very 
>aerobic
>>inertially homeothermic ectotherm).
>
>Does this comment essentially suggest an animal that has a "mammalian"
>lung capacity/structure (if you will), but is essentially 
>"gigantothermic" in the sense that its variance in body temperature 
>relies on slow cooling due to a large body mass?

That was exactly what that comment suggested.

It doesn't mean that I believe that that was the thermal ecology of
_Scipionyx_, only that the non-parenthetical statement was what Ruben et al.
describe for the critter (and the parenthetical comment would be implied by
the same sort of aerobic capability in a larger critter).

Luis Rey wrote
>>Techincally speaking, endothermy is NOT the ability to be active, dynamic,
>>etc.  It ISN'T the same thing as homeothermy.  It is simply internally
>>generated heat.  Period.
>
>I was talking in general terms.

That's what I figured, and therein lies the problem.  What Ruben et al. were
arguing requires using specific terms: level of behavior which we see in
modern mammals oxygenating at a high rate (powered by the supposed
liver-pumped lungs) while lacking the subcellular ability to generate heat
internally.  (Note that this would have the advantage of not requiring as
much food as an tachymetabolic endotherm would need).

>In any case I'm talking about internal thermal regulation (versus being
>dependent on the environment). Strategies vary.

That would be homeothermy vs. poikilothermy, a different topic.

>That is precisely what I'm arguing against (I agree with the arguments of
>Greg Paul,among others). I think they have no proof whatsoever and besides,
>they rely in vague interpretations of fossil traces.
>They got it wrong with Sinosauropteryx before... and they are getting it
>wrong again.

I do not necessarily disagree with you (he said, diplomatically).

>Needless to say I have no authority to make conclusions, but as a humble
>artist I think I looked to the Sinosauropteryx protofeathers more
>objectively than the Oregon Team did. Phil Currie's detailed photographs of
>the hollow 'quill-like' structures corroborated what I had seen with just a
>magnifying glass.

Actually, you have just as much authority as anyone else: the ability to
observe, compare, suggest, and test.  I agree with you that I am not
convinced with their interpretation of the the integumentary structures, nor
their evidence for a hepatic piston.

>I have also seen first hand all the Scipionyx photographs and have talked
>at length with Cristiano Dal Sasso (a wonderful and open person whose
>expertise is beyond any doubt). The famous 'diaphragm muscle traces'
>actually lay underneath the intestines (to my eyes).
>Cristiano defended the location of the liver, but didn't agree completely
>with >all< of Ruben's interpretations.
>Everyone is still making their mind about the matter.

As they should.  I haven't made up my mind on it, either.

>And I don't like the Oregon Team 'presentation tactics' neither. By
>'tactic' I mean simple things like reiteratively showing slides comparing a
>crocodile and a theropod pelvis always SIDEWAYS. There's a much bigger
>difference when you show them in a frontal view!

Oh, my, how I agree with you there!!  Modern croc & theropod pelves are
very, very, very different.  Although you *might* be able to create some
kind of hepatic piston system out of a theropod pelvis, you can't create a
mobile-pubis croc-style hepatic piston out of a theropod pelvis.

I agree that basal crocdylomorphs and theropods had pelves much more similar
to each other, but because these early crocodylomorphs lacked mobile pubes,
they too would not h be able to have the same kind of dynamic hepatic piston
as a modern crocodilian.  (Doesn't mean that didn't have some kind, just not
the same kind).

As a weird aside, the Ruben et al. conclusion of the thermal and aerobic
ecology of theropods actually doesn't need a hepatic piston at all, only the
ability to oxygenate at some greater rate than typical modern squamates,
turtles, etc.  In fact, if you used the Classens/Carrier/Farmer
gastralia-driven lung system (with or without air sac assistance) you might
still produce a well-breathing animal with or without an endothermic physiology.

Mere speculation, I admit.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661