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Re: What is an "active ectotherm"?



A partial quote of DinoGeorge's response to my query about active ectotherms:

> Do fish count? Water has a much higher specific heat than air and is
>   a much more effective cooling agent. Yet many fish can contrive to
>   swim perfectly well through a medium whose temperature would kill
>   an unprotected human in minutes. They're mainly ectothermic, but
>   they generally keep moving around their fish tanks. How about
>   sharks? How about insects? These are all examples of active
>   ectotherms. Why couldn't dinosaurs be likewise? 

Those are good examples.  I know that under normal circumstances, sharks
MUST keep moving or drown.  Insects, except for maybe bees, wasps, and some
moths, would seem to more dependent on the temperature of their
surroundings.  Ants, grasshoppers, etc., as well as other arthropods
(spiders, crabs, lobsters, centipedes, etc.) become quite sluggish as the
surrounding temperature gets lower.  They eventually become dormant if the
temperature gets low enough.

In any case, I was hoping for an example of a terrestrial (in the sense of
not dwelling in the water), vertebrate "active ectotherm" -- an animal that
could be used as an analogue for the type of creature that has been
hypothesized as an antecedent or ancestor to endothermic birds (and possibly
dinosaurs).  Is there, or has there definitively been proven to have
existed, such a creature?

"Inquiring minds want to know."

Andrew Howey    ajhowey@ix.netcom.com