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Re: Part 2: Terramegathermy (becoming longer again...)



> > There could always have been a counter-current heat exchange system
> > in long, thin tails (thick ones are not so much of a problem IMHO),
> > like in bird feet, no? (If it was necessary.)
>
> Perhaps; though it does make me wonder why such a thing never seemed to
have
> evolved in weasels, but then, mammals always seemed to do things
differently.

I mean _thin_ bird feet, just bone, tendons and skin. The heat exchange
system enables birds (ducks, gulls, maybe all, I don't know) to keep their
feet poikilothermic -- there are no muscles there that require a constant
high temperature -- nearly without losing heat. This is why birds can walk
on ice for hours.
        I wonder what there is in, say, rat tails...
        Weasels, however, aren't so terribly long and thin, I don't think
they need anything special for keeping warm.

> > Well, birds _normally_ have nearly double resting metabolic rates of
> > placental mammals. I have found numbers at the library in a book on
> > marsupial biology, have yet to copy them.
>
> Birds yes, but dinosaurs

Just as an example that not all "warm-blooded" animals lie within a narrow
range of RMRs.

> (please no cladistic pedantry >:)?

... "but other dinosaurs"? :-)

> Again, early bird bone studies (for what good they are) seem to indicate
> slower rates of growth than modern birds. It might not have been
> bradymetaboly, but it didn't seem to be hyper-avian metaboly either.

May have been more like the placental level of tachymetaboly... I'll look
for the numbers on Monday, the differences are enormous.

> > > Ah, but varanids are highly active and still retain their sprawling
> > > stance.
> >
> > Because they have evolved the famous gular pump that allows them to
> > breathe during running. Crocs have the famous hepatic-piston pump for
> > this, and ornithodirans apparently had neither, instead they evolved
> > erect stance.
>
> But an erect stance *doesn't* free one from this carrier's constraint.

Sorry, true, but a rigid trunk (present in all ornithodirans, and AFAIK
rauisuchians) that prevents lateral undulations does.

> At
> least one species of crocodylian today (_C.niloticus_) has an erect stance
> (pers. observ)

Semi-erect? (Pers. obs. on TV.)

> _Protosuchus_ has a pelvic girdle that would indicate no diaphragm present
(or
> a very simple one)

While none probably contradicts what I've said above, a simple one
doesn't...

> yet we also
> have the erect and bipedal _Eudibam[u]s_.

Erect, yes (more or less); bipedal -- not always, the forelimbs were also
erect and well adapted for locomotion, just shorter.

> The more I think about it, the more
> confusing it becomes.

Now we're already two! :-)

> As for ornithodirans without these pumps, do we not have slight evidence
of
> diaphragms in ornithischians. And could it not be archaic to all
dinosaurs; as
> _Scipionyx_ *might* (note I did say ->might<- ) indicate.

I still wonder why nobody started a flame war on this >:-> -- just
http://www.dinosauria.com/jdp/misc/scipionyx.html,
http://www.dinosauria.com/jdp/misc/lungs.html. BTW, Ciro is flattened like
most other fossils, so the "domelike" outline of the red-purple stain (be it
the liver or whatever) means just about nothing.

> > > and how cold were these polar
> > > nights?
> >
> > Around 0 °C AFAIK. Months of darkness don't allow for much more.
>
> I suppose they wouldn't; what about other flora and fauna?

No classical reptiles are known from polar localities AFAIK, even though
they come quite close (champsosaurs in the Canadian Arctic). There is
*Koolasuchus* in polar EK Australia, but some amphibians can be active even
in melt water of snow, while no reptiles can.

> Anyway, the general consensus I seem to get among pro-L.C. endotherm
> paleontologists today is that dinosaurs had higher MRs than reptiles, but
were
> still lower than or equal to mammals. I don't know of very many that
believed
> that they had avian metabolisms (which would seem extremely wasteful for
such
> large animals IMHO).

Equal to mammals is just fine IMHO. Avian metabolism may have been reached
by particularly birdlike particularly small theropods IMHO, but this is of
course speculation.