Re: Mamenchisaurus Posture Paper

[David Marjanovic <david.marjanovic@gmx.at>]

----- Original Message -----
From: "Roger Seymour" <roger.seymour@adelaide.edu.au>
Sent: Saturday, May 21, 2005 3:43 AM

> I have been pointing out that the cardiovascular system in sauropods could 
> not
> have allowed them to raise their heads very high.  The first paper was a 
> short
> one in Nature in 1976, but in the meantime, I have gathered better data on 
> what
> cardiac muscle is capable of.  The results have appeared in the 
> comparative
> physiology literature, but when applied to sauropod dinosaurs it shows 
> pretty
> clearly that they didn't raise their heads very high.

What do you think of the idea that various tricks might have helped? Valves 
in the neck arteries? Perhaps even contractile arteries?

Ignorant question: How does heart power scale with heart size? Muscle 
strength is supposed to scale with muscle cross-sectional area, and this 
should scale with the... volume of the heart? In this case the absolute size 
of the heart would merely need to scale with the height of the head above 
the heart. This in turn would mean that there would be a limit on relative 
but not absolute head-above-heart height (as long as the blood pressure 
wouldn't blow anything apart, of course). Is it this convenient?

> Two meters above the heart would probably have
> been about the limit.  That's what giraffes do.

Isn't that more like three meters, or perhaps four in big bulls?