Re: 4-CHAMBERED ECTOTHERM

["Nicholas J. Pharris" <pharrinj@PLU.edu>]

On Fri, 26 Jan 1996 Dinogeorge@aol.com wrote:

> This brings up the point that mammalian endothermy isn't quite as complete as
> that of birds. During hibernation, mammals effectively become ectotherms. I
> can see how a burrowing mammal might evolve ectothermy as a modification to
> its hibernation physiology.
> 
> I could live with croc ectothermy being secondarily derived from some similar
> kind of incomplete thecodontian endothermy.

I didn't mean to suggest that the earliest thecodonts were full 
endotherms of the bird mold.  I think it most likely that they (and most 
nonmammalian therapsids) had a level of endothermy somewhere up to that 
of a monotreme or insectivore.

> Are there any birds that hibernate? Any ectothermic birds?

No known ectothermic birds that I know of (I have serious reservations 
about the "growth rings" found in that South American enantiornithine).  
Most birds are, as suggested above, "better" endotherms than mammals.

As I recall, hummingbirds go into some sort of nightly hibernation to 
avoid starving to death at night.  As always, correct me if I'm wrong.

Nick Pharris
Pacific Lutheran University
Tacoma, WA 98447
(206)535-8204
PharriNJ@PLU.edu

"If you can't convince them, confuse them." -- Harry S. Truman