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PHYSIOLOGY.... YAWWNNN II



OH NO! NO! NO! NO! NO! ARGHHH! Not the physiology debate again!

Without launching into the palaeoclimes, pred-prey, anatomy etc. arguments that
everyone else is harking, I thought I'd contribute some kind of spanner-in-
the-work thoughts. 

Most of you are aware of the histological work that complicates (or clarifies,
depending on your opinion) interpretations of archosaurian physiology. By this
reckoning, theropods were ectotherms, while certain ornithischians were
endotherms. Now some people just think that that's plain stupid. Early birds
weren't warm-blooded but ornithopods were? Yeah... right (any opinions expressed
here are not necessarily those of the author...). 

However, this research and other material SUGGESTS (I don't know what to
conclude really) that archosaurian physiology was more 'flexible' than that of
other groups we are familiar with. The latest theory I hear, written in an as-
yet-unpublished manuscript called 'Dinosaur Thermal Strategies', is that
archosaurs could revert to (more jargon) a bradymetabolic (essentially
ectothermic) way of doing things, depending on climate or possibly food
availability, but were primitively tachymetabolic (essentially endothermic). So
adaptable were archosaurs in this regard that even two closely related species
could possess disparate physiologies... (Chinsamy's look at _Protoceratops_ and
_Pachyrhinosaurus_ bones resulted in a similar conclusion, as did Jim Farlow's
work on physiology in Weish, Dod & Os).

All this stuff blurs distinctions between 'warm' and 'cold' blooded animals.
Recent discoveries in physiologies of extant species also show that things are
more complicated, and often more subtle, than lay interpretations. Certain of
the scombroid fishes, things like marlin and tunny, for instance, are capable
of generating internal heat within (e.g.) their eyes. This ability has evolved
in parallel amongst various of these fish groups - yet fish are always thought
of as ectotherms. It's fairly well known that sharks (esp. _Carcharodon_), use
their own digestion to heat themselves. Are they really, then, ectothermic?

Conversely, an extant mammal has now proved that tachymetabolic animals can
revert to bradymetabolism where it is not advantageous. The naked mole-rat
(_Heterocephalus glaber_) is ectothermic, unable to generate its own body heat.
This 'reversal' of physiology has, it seems, evolved because endothermy was not
necessary in the mole-rat's subterranean tunnel system. And this, I think, is
a pointer for a further interpretation. Endotherms can, therefore, revert to
ectothermy when the need arises. They are not trapped in a physiological cul-
de-sac. So the fact that all those big mammals out on the savannah, in the
baking sun, are still endothermic suggests that endothermy out in the tropical
heat is an advantage. It must be anyhow, or big tropical endotherms wouldn't
be so successful. THAT, I think, is more weight for the tachymetabolic
physiology of dinosaurs. Are ya bored yet? WHO started this??


"Hey man, the west is the best, it's all here - fer sure! But ya gotta have
wheels out here, man, and Wendy really digs my van 'cus I got diamond-pleat
seats. And, man, listen to that sound system! We're both vegetarians. Me and my
board have been through a lot together and, sometimes, after a day out surfing,
I like to go back to the pool and relax with the guys, while other times I seek
to find myself with the calm beauty of nayture..."  -- The otter that wins the
high-dive in Animalympics.

BECAUSE I WEAR A WOLF-SKIN SOMETIMES PT. II

'The girls looked at each other with fear in their faces and fled.

'When the boy, Jean Grenier, was apprehended, he confessed to many crimes. He
said he had dragged a child from its cradle, and devoured it. He had also
attacked a girl as she was keeping sheep - he tore at her with his nails and
teeth, and ate her.

'In 1603, a French court sentenced the Grenier boy to perpetual imprisonment in
the walls of a monastery. Because of his youth, Jean Grenier had been spared his
life....'

"Will they die?"  "Difficult to see. Always emotion is the future..."
"It has been estimated that conservation all over the world needs each year }
million [pounds]. This is no astronomical figure. It is half the price of a V
bomber, less than one twelfth the price of a new Cunarder, or the price of, say,
3 or 4 world-famous paintings..."
"While American business men snap up Van Goughs at the price of a hospital
wing..."

DARREN NAISH