Re: Warm-Blooded debate

["Michael" <tons@ccs.netside.com>]

> Date:          Tue, 17 Jun 1997 21:46:06 -0700
> Reply-to:      jwoolf@erinet.com
> From:          Jonathon Woolf <jwoolf@erinet.com>
> To:            brucet@mindspring.com
> Cc:            dinosaur@usc.edu
> Subject:       Re: Warm-Blooded debate

> bruce thompson wrote:
> > 
> >         There exists a scholarly monograph from about 15 years ago called
> > _A Cold Look at the Warm-Blooded Dinosaur_  or something like that.  I
> > never read it; could anyone supply the author(s)?
> 
> "A Cold Look at the Warm-Blooded Dinosaurs" is the published transcript
> of the proceedings of a conference held around 1980.  I've never seen a
> copy, it's apparently very rare, but it casts a very skeptical (one
> could almost say jaundiced) look at the evidence as it was known then
> for dinosaurian endothermy.  However, "the evidence for dinosaurian
> endothermy" in 1980 amounted to upright posture, _Deinonychus_'s
> obviously active nature, a few meager bone-histology studies, and
> Bakker's admittedly tenuous predator/prey ratios.  No one had yet heard
> of:
> 
>       * High growth rates in hadrosaurs 
>       * Complex social behavior in hadrosaurs
>       * Long-range migration by hadrosaurs and ceratopsids
> 
> 
> >         I don't see why it is such a stretch for dinosaurs to have been
> > ectothermic.  As evidenced by palm tree fossils near the Arctic Circle in
> > Alaska, the earth was much balmier then.  Under such conditions ectotherms
> > could have powered up much more cheaply than they can now, and could have
> > been as active as we now suppose them to be.  
> 
> The difference between ectothermy and endothermy is not simply a matter
> of "powering up."  Endotherms don't simply have more energy, they have
> more endurance and a very different cellular chemistry.  Ectotherms have
> no endurance because they can only generate energy anaerobically.  (A
> lizard or a crocodile has to kill in its initial rush -- if it doesn't,
> it has no energy left for a second attempt.  That's why all modern
> reptiles are ambush hunters.)  Endotherms like mammals and birds can
> generate energy both anaerobically and aerobically.  No anaerobic
> organism could have developed the energy for hours of steady cruising at
> ten or twenty strides per minute, as hadrosaurs and ceratopsids must
> have done on their migrations.  
> 
> > Some dinosaurs did have sails similar to the pelycosaur Dimetrodon--why
> > should those sails have been used for any different purpose?
> > 
> 
> There's no certain evidence that sails in _Dimetrodon_ or _Edaphosaurus_
> were primarily for thermoregulation.  Closely related pelycosaurs did
> just as well without sails.  It's entirely possible that the sailbacks
> had sails for display, like the frill on a frilled lizard.
> 
> -- JSW
> 
That' an interesting point about sails.  I would like to politely 
disagree about metabolism.  I don't think the cellular chemistry is 
that different between endotherms and ectotherms (relatively 
speaking).  Mammalian mitochondria are more evolved and efficient 
than reptilian but not greatly so (membraneous, receptor,etc).  The 
difference between ectotherms and endotherms in regards physical 
activity at the same body temperatures are also not that different 
with a linear curve resting below but rising with mammals.  

Stamina has more to do with the type of musculosketal system, muscle 
fibers and numbers of mitochondria, circulatory system, medium in 
which locomotion takes place, and the energetics of locomotion.

In general, the rate of oxygen consumption in excess of the basal 
metabolic rate increases linearly with the velocity of locomotion.  
The increase in energy use per unit weight per unit speed is greater 
in small vs large animals with each animal having its own "curve".  
Interestingly, wallabys can reach a speed at which further increases 
in speed  do not increase VO2.

So, there are a lot of reasons why Kamodo Dragons can't outrun deer 
over distance. 

As always, this is only an opinion, subject to
retraction and recall without notice, and with 
due respect to others opinions.

Thanks,

Michael Teuton MD