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Re: Warm vs Cold blooded
Ok, I guess it's time for a little cross-fertilization. About a month
and a half ago, we had a raucous good time over in VRTPaleo discussing
whether or not dinosaurs were endothermic. At the end of that
discussion, none other than John Ruben chimed in with
a... strongly-worded, yeah... that's what I was looking for :-)
statement that we don't really have any idea whether or not dinosaurs
were endothermic. Rather than paraphrase, I'll give you his words
Wake up guys-- there's abundant evidence out there in the
physiological literature that bone histology has little or nothing
to do with metabolic rate. It's more closely tied to growth rate
(which also often has little or nothing to do with metabolic rate).
Those of us concerned with determining metabolic rate in extinct
taxa need to do a lot more homework re the physiological literature.
The bottom line here is that there are presently NO described
preservable features which are especially reliable indicators of
metabolic rate in fossil taxa, dinosaurs or otherwise. This will
all change very soon (within the next few months), but for now,
forget histology, trackways, posture, predator/prey ratios, growth
rates, bone isotope ratios, etc., as indicators of metabolic
rate. None of these stand up to close scrutiny.
You hot-blooded dino folks-- please don't deluge me with the
paleontological equivalent of hate mail. If you really must know
why the supposedly heretical dinosaurs were really probably pretty
Ruben,J. 1995. The evolution of endothermy in mammals and birds: From
physiology to fossils. ANNUAL REVIEW OF PHYSIOLOGY, 57:69-95.
Another article you might like to find in trying to understand
thermoregulatory strategies is:
Block, B. A. and Finnerty, J. R. (1994). "Endothermy in Fishes: A
Phylogenetic Analysis of Constraints, Predispositions, and
Selection Pressures", _Environmental Biology of Fishes_,
I argued over in VRTPaleo that thinking of endothermy as an either/or
characteristic is probably counter-productive. Fish and insects
represent interesting cases for consideration in that regard.
Mickey Rowe (firstname.lastname@example.org)