Insulation does not = "Warm-blooded"[Was Re: Ornithodira, breathing with long necks]

[archosaur@usa.net]

"David Marjanovic" <david.marjanovic@gmx.at> wrote:

>Anyway, considering the fact that *Archaeopteryx* and all birds for
> which feathers are known are insulated all over their bodies, none of them
can possibly have been ectothermic, because insulation restricts heat
> exchange with the environment.

++++++++++++++++++++

Ah, but as it restricts the ability to attain heat from the environment, so
too does it restrict the ability to lose heat to the environment. So if your a
fast living ectotherm covered in heat retaining feathers and your flitting
about, then all the heat generated by those muscles (be they ecto or endo)
would get trapped in the body, effectively removing the need to warm up
ectothermically. The only problem then would be in keeping from heat
exhaustion.

And besides, we have extant "cold-blooded" animals today with insulation
(lamniforme sharks, _Dermochelys coriacea_, moths, bees and spiders).

--------------------------

>About bones... some people think that enantiornithines were
> ectothermic because of the LAGs (lines of arrested growth) in their bones.
This conclusion has turned out to be nonsense, at least in hadrosaurs. I'm
sure this has been discussed ad nauseam onlist; if you want, I can dig up some
papers on this subject.

++++++++++++++++++

Well, I dont' know if Rob would want them, but I certainly would. If anything
all these bone histology studies have shown is that they are useless in
determining endo/ectothermy (or poiki/homeothermy, brady/tachymetabolism;
whichever is more appropriate). 


Jura - probably the only listmember who advocates bradymetabolic dinosaurs and
enantiornithines.


Jurassosaurus's Reptipage: A page devoted to the study of and education on,
the reptilia:

http://reptilis.net

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