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What is an "active ectotherm"?



I've been reading this "origins of birds/origins of feathers" thread for a
while, and several people have used the term "active ectotherm".  Could
somebody please give an example of such an animal?  I'm having trouble
understanding what is meant here.  DinoGeorge said that such a creature
would have/need "just a good circulation with a quadricameral heart".  The
only ectotherms I know of with four-chambered hearts are the crocodilians,
and they're not all that active, spending much of their time basking.  Are
there any present-day examples of "active ectotherms"?  Sorry for specifying
you, DinoGeorge -- you just happened to give some of the physiological
requirements for such a critter.  I posed the question so that I can better
understand the varying points-of-view.  
As I understand the term "ectotherm", such an animal is dependant on the
ambient air or water temperature to bring the body temperature to a point at
which the physiological processes can occur.  The warmer the ambient
temperature, the more more active an ectothermic animal can be -- to a
certain point.  If the ambient temperature is too high, then the animal must
seek shade or risk frying.  However, even in the tropics, where the air
temperature is pretty close to ideal most of the time, in terms of
physiological processes, most ectothermic animals still aren't all that
active compared to a comparably-sized bird or mammal.  Is there something
I'm missing?  I'm just a rank amatuer compared to most of you, and I want to
understand the discussion better.

Thanks in advance for any clarification any of you might want to give.

Andrew Howey    ajhowey@ix.netcom.com