Re: Warm-blooded debate

[Joshua Dyal <j-dyal@geocities.com>]

Dinogeorge@aol.com wrote:

> Any adult sauropod will do, I'd say.

<snip>

> All we know is that modern birds are fully endothermic, so complete
> endothermy must have developed >somewhere< in the lineage leading to birds
> from the common ancestor of birds and crocodiles (which aren't endothermic).
> Indications are that adult fully endothermic sauropods would have overheated,
> particularly since they have no known anatomical structures with which to
> dump excess body heat, so full adult endothermy >likely< developed in the
> aforementioned lineage leading to birds >after< the sauropods diverged.
> 
Isn't it true, though, that in tropical scenarios where overheating is a
danger, that large endotherms have much less to worry about that small
endotherms because their large size insulates them from overheating
rapidly?  I think it is telling that the only really large endotherms
today (well, most of them, anyway, the terrestrial ones besides bears)
live in dry tropical climates (like the Serengeti) where they would,
according to your idea above, be the most susceptible to over heating. 
The sauropods, being WAY larger than elephants and rhinos, would have
had an even harder time overheating, because by the time their massive
bodies got even close to overheating, it would be night, and they could
cool down again.  I was just rereading PDW by GS Paul, and I just read
his chapter on endothermy last night, BTW.  He discusses this issue at
length there.

<more snippage>

> No way to confirm this scenario, but it fits the known growth-rate profiles
> of dinosaurs as well as any.

It also fits the growth profiles of most large mammals too, though,
doesn't it?  Relatively quick growing juveniles, then growth slows way
down or stops altogether as adult size is reached.

Joshua Dyal
j-dyal@geocities.com