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Re: Warm- vs. Cold-blooded Dinos
>From: firstname.lastname@example.org (James Shields)
> Everyone so far seems to be in favour of endothermy. While I think it very
> likely that some dinosaurs were endothermic, I am not at all convinced that
> all, or even most were.
> Dave's evidance does apply very well to small theropods. They would probably
> need an endothermic metabolism to maintain their active lifestyle.
I would go slightly further and state that there is some evidence
that the *sauropods* were ectothermic.
> But that is not to say they were warm-blooded.
> Sea turtles manage to keep an almost constant body temperture, not through
> endothermy, but "gigantothermy". I don't know of this is a real term.
And it really applies mainly to sauropods among the dinosaurs.
On land an animal needs to be larger to achieve bulk homeothermy
than in the water - water temperatures vary *far* less with time
than air temperatures.
Except in tropical climates, I do not think anything much smaller than
a sauropod could effectively achieve bulk homeothermy. Many dinosaurs,
including large plant eaters, like ceratopsians and hadrosaurs, are
known from the arctic regions. Even in the warmer world of that time,
these areas were quite cold from a metabolic point of view (average
annual temperature about 5 degrees C.). Even allowing for a certain
amount of migration, their winter home would have been a good deal
colder than a viable body temperature. [Despite what has been published,
migration from the north slope of Alaska to some place in the lower 48
is not likely - no known living animal migrates anything like that far].
The peace of God be with you.