Re: CROCODYLOMORPH ENDOTHERMY

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

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

> This doesn't mean I _don't believe_ that dinosaurs were endotherms; it's just
> much more a matter of faith than of science. Dinosaur endothermy is a simple,
> unifying explanation for a lot of otherwise disconnected observations about
> dinosaurs, such as bone histology, predator-prey ratios, erect stance,
> footprints indicating a high level of activity, suppression of coeval
> mammals, and phyletic proximity to birds. That's why I think dinosaurs were
> endothermic to some degree or other. But many of these observations do not
> extend back to thecodontians, so thecodontian endothermy is correspondingly
> much more problematic. We don't need thecodontian endothermy to have
> dinosaurian endothermy, for example.
> 

OK.  Points taken, and I'm sorry, all of you, for being such a pill in 
this respect.  It just looked to me like early crocodiles like 
_Terrestrisuchus_ and _Gracilisuchus_, as erect, active-looking animals, 
should be examined as potential endotherms.  My ideas were also spurred 
by my rereading of the assertion by Bakker in _The Dinosaur Heresies_ (I 
know, grain of salt) that erythrosuchians and warm-blood-style, plexiform 
bone.

Many rauisuchians, poposaurs, and ornithosuchids also look like very 
active animals and also should be checked for bone structure.

I see endothermic adaptations as most logically coming in the following 
order:

four-chambered heart -> endothermy (to some extent) -> erect limbs.

As I see it, a four-chambered heart is a prerequisite for a truly 
endothermic physiology; and endothermy would be required for the stamina 
to stand erect.

You are free to disagree.

There are plenty of researchers out there acting like we should assume 
ectothermy for dinosaurs until endothermy is proven without a doubt.  We 
will never know for sure, as Dinogeorge said, and I do not believe it 
will hurt anything if I continue to believe that all dinosaurs were 
endothermic until ectothermy can be proven beyond a doubt.  The evidence 
just seems to make more sense that way.

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