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Re: CNN:Is it snowing in Oregon?



At 08:50 AM 1/22/99 +0000, Luis Rey wrote:
>Finally news! The Oregon Team have back down and agreed that dinosaurs were
>warm blooded!

Whoa there, Tex.  NOT that I agree with everything Ruben et al. have to say
on this matter (surprise), but to be fair they do not say that dinosaurs are
warm-blooded.

>Cold-blooded as a reptile with the metabolism of a mammal or a bird??? One
>thing or the other or both? Technically speaking, having a mammal or bird
>metabolism would imply just that: warmbloodedness, or if you prefer
>homeothermy or endothermy, no matter what 'type' or what strategy is used,
>the inner temperature and metabolism are still controlled internally, and
>NOT just regulated by the environment.

Endothermy: the ability to generate *heat* internally by subcellular
mechanisms.  Period.

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.

What Ruben et al. are suggesting is that theropods, with the alledged
hepatic piston lungs, would be able to maintain a level of activity
comparable to modern birds and mammals even though they were not
*generating* heat internally.

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).

>>>"They can sprint," he said in a telephone interview. "The difference is
>that warm-blooded animals (such as birds and mammals) can maintain this
>for a lot longer. They have a lot more stamina. And that is what we are
>saying the  theropod dinosaurs had."
>
>Here it is: finally the Oregon Team agree that dinosaurs were not crocs or
>reptiles and were warm blooded, since they didn't have 'reptilian'
>metabolism and were much more like birds and mammals than crocodiles.

Again, they are not saying that they were "warm-blooded" (a grossly
misunderstood term: this is the reason physiologists distinguish between
ecto- & endothermy, homeo- & poekilothermy, brady- and tachymetabolic,
etc.).  And, in fact, they say:

"However, relatively low aerobic capacity iin recent crocodilians, all of
which are aquatic, might not represent the ancestral condition.  Early
(Triassic) crocodylmorphs (for example, _Protosuchus_ and _Terrestrisuchus_)
might have had enhanced aerobic cpacitites because they appear to have been
fully terrestrial and cursorial with habitually upright limb postures."
-p. 516

[An aside: jeez, that sounds familiar, doesn't it, Greg?...]

>>>So they would be as quick and ruthless as a crocodile, with the stamina
>of a modern-day carnivore such as a lion.
>
>Right, so we know now that dinosaurs were crocodiles that behaved
>metabolically like a lion.

Actually, they are suggesting that dinosaurs were metabolically like
crocodiles but behaved lke lions...

>'Breathing like humans and mammals' (their words not mine), but hey, STILL
>A REPTILE (Please note that the term is used here as an archaism).
>Dinosaurs were mammal-mimics. They just pretended to be warm blooded.

Yeah, that's what they are going for.

>They ceased to be 'turbos' when the environment went cold... what happened
>with all the energetic mammal-like crocs stuff?

Again, if you understand their model, they are suggesting that dinosaurs
were incapable of generating heat internally.  As such, they would be
susceptible to long term temperature changes, even if they were were
"turbo-charged".

>And all despite that
>there's no evidence of immediate cooling of the climate from the Cretaceous
>to the Paleocene (please can someone provide evidence for a Paleocene Ice
>Age?) , and the fact that dinosaurs lived happily in the seasonal North
>Pole for a very long time.

*BING*  Now, there we go.  A chance to evaluate the model by testing it
against the record.  And, yes, the presence of dinosaurs (including little
ones) in environments in which known ectotherms are not found (like the
early Maastrichtian of the North Slope of Alaska) does suggest a greater
environmental tolerance for dinos than lizards, crocs, turtles, and
champsosaurs (which are a dime a dozen in equivalent strata in Alberta and
Montana).

However, I am glad to see that the idea is getting out beyond the scientific
community that the "warm-blooded"/"hot-blooded" dichotomy simply isn't:
there are a variety of aspects to thermal physiology AND activity levels AND
growth rates AND paleoecology AND etc. that should be explored.

>And all this coming from the people that mistook fossil slab's glue for
>Sinosauropteryx internal organ traces and combed dead sea snake tissue to
>made it look like Sino's protofeathers.

(Don't forget the decaying _Varanus_, too...)

Be that as it may, remember we are evaluating the concepts proposed, not the
people.

Funny, but it seems to me that there are many individuals on this list who
have claimed that the ideas of Greg Paul aren't supported because "he is
just an artist", to which others have (rightly) responded: judge the
evidence presented by its merits.  Should we do less here?

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