RE: Biomechanics

[Toby White <augwhite@neosoft.com>]

The giraffes are more interesting, but I'll stay on topic...

This problem is discussed in Paladino et al's article in the Complete Dinosaur. 
 Giraffes, elephants, etc are only minimally relevant because they have 
diaphragms and (compared to the bird-croc bracket) huge lung volumes.

Paladino et al cite Hengst & Rigby (1994 Dinofest) for the estimate that 
Apatosaurus had a lung volume of 1400 l with a dead space of 184 l.  Sounds 
like a reasonably serious physiological constraint to me, but who knows how 
good these numbers are?  At any rate, sauropods were not notably barrel-chested 
and also had to maintain hearts that must have been large and strong (recall 
the blood pressure discussion).  The problem must have been solved somehow, but 
how?  Paladino etc. try their hand at allometric scaling from birds. 
 Interesting, but how realistic is this?  There are no 30,000 kg birds -- at 
least not on my bird feeder -- and scaling up three orders of magnitude 
requires too large a leap of faith for me.  Even assuming avian respiration, 
they cannot get the overall metabolic rate up much above the Poriferan level.

Beats me ...

  --Toby White

On Thursday, September 09, 1999 12:17 AM, k. clay [SMTP:clayke@pacbell.net] 
wrote:
>
>
> tons wrote:
>
> > Well they both can get you but dinosaurs would have no way to breathe
> > pressurized gases.  I was using the analogy of dead space which if
> > increased
> > causes increased CO2 partial pressures in the lungs and hence equalizing to
> > the body.  Sauropods have long necks and therefore (probably) a lot of dead
> > space.  I haven't had the time to look at giraffe physiology but would love
> > a quick freebie from someone.
>
> > I too would love a quick freebie from someone, but let's talk about giraffe
> > physiology instead.  I refer you to:
>
> Langman, V.A., et al.(1982)  Respiration and metabolism in the giraffe.
> Respir
> Physiol 50(2):141-152.  "...contrary to statements in the literature the
> giraffe
> does not have an abnormally large dead space, though the trachea is
> abnormally
> long and narrow.  The respiratory measurements indicate that the giraffe
> breathes as predicted by published scaling equations, and at rest shows no
> abnormalities of rate or depth."   Hope this helps. Cheers to Michael and
> Matthew for an interesting physiology discussion.--Ken Clay, M.D.
>  << File: ATT00009.html >>