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Re: Mamenchisaurus Posture Paper

----- 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?