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Re: basking and thermoregulatory physiology (was Re: Feduccia's errors)
Mickey P. Rowe wrote:
> Greg Paul wrote:
> > There is no evidence that ectotherms dependent upon large amounts of
> > environmental heating can afford to be insulated.
> I'm *not* going to get dragged back into this, but from my perspective
> it seems people focus way too much on extreme positions (I think it
> was two years ago that I was making the same arguments over on
> VRTPaleo, and in that case I was arguing with someone who seemed
> overly confident that dinosaurs were ectotherms...). Endothermy (as
> practiced by modern mammals and birds) results from suites of
> characters. It's not just one thing, so you can't a) give one of
> those characteristics to a modern ectotherm to demonstrate the
> impossibility of that trait's existence without the rest of the suite
> and b) conversely you can't conclude that because an animal had one
> character from the suite that it had them all (at least not to the
> degree that modern endotherms have them).
Let's hear it for a moderate viewpoint.
> Note that this is different from the RT argument. In that case, the
> argument is that no animal can have the chronically high metabolic
> rates (resulting from a suite of characters) of modern endotherms
> without some mechanism for retaining respiratory water. IMHO, the
> only thing left to argue on this point is whether or not there is any
> evidence that dinosaurs had such a mechanism.
How is this different from the RT argument? Just becuase they don't
appear to have had RTs, allegedly, doesn't mean that they didn't have
other mechanisms, which would most likely not have been fossilized
anyway. The mechanism probably had behavioral components that no way
are we going to see. This is sort of like Spotila and Dodson's argument
saying that sauropods couldn't have been endothermic because they
couldn't dump heat fast enough. Then they go on to show that according
to Spotila's models, neither can elephants (the answer here is that
elephants handle the heat stress behaviorally and Spotila and Dodson
refuse to allow sauropods the same advantage).
> Finally, I confess I haven't done all of my homework with respect to
> invertebrates (there are a couple of books by Bernd Heinrich that I
> think ought to be widely read by participants of these discussions).
> I suspect some fuzzy little bugs may prove Greg's contention wrong.
> If anybody gets (or has gotten) to these books first, by all means
> enlighten us!
> As it happens I have read some of them, although its been a while, and
I was more interested in their chemical ecology at the time.
Unfortunately, the insects can't be used to prove Greg wrong. They are
small enough that the supposed "insulation" is completely ineffective at
preventing heat transfer in any significant quantity. Besides, they can
operate at significantly lower body temps than endotherms can, they just
slow down when they get cold. But, because of their small size they can
pick up heat readily from the environment. There are some near Arctic
insects that buzz around quite merrily in the inflorescences of flowers
that serve to collect heat (raising the temp inside the inflorescence by
as much as 15 C, and this not counting the beneficial effects of shelter
from the freezing wind). Their size also gives them the advantage that
muscle movement and basking is far more effective for warming them than
it is for bigger animals. Back to this behavioral thing again:)