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Re: Sauropod Energetics (Peristaltic pumps for arteries?)



The following article discusses why such a solution to
high blood pressures in rearing sauropods is unlikely:
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Proceedings: Biological Sciences 
ISSN: 0962-8452 (Paper) 1471-2954 (Online) 
Issue: Volume 267, Number 1455 / September 22, 2000

Pages: 1883 - 1887 
DOI: 10.1098/rspb.2000.1225 
URL: Linking Options  
Hearts, neck posture and metabolic intensity of
sauropod dinosaurs

Roger S. Seymour A1 and Harvey B. Lillywhite A2 

A1 Department of Environmental Biology, University of
Adelaide, Adelaide, South Australia 5005, Australia
A2 Department of Zoology, University of Florida,
Gainesville, Florida 32611, USA

Abstract: 

Hypothesized upright neck postures in sauropod
dinosaurs require systemic arterial blood pressures
reaching 700 mmHg at the heart. Recent data on
ventricular wall stress indicate that their left
ventricles would have weighed 15 times those of
similarly sized whales. Such dimensionally,
energetically and mechanically disadvantageous
ventricles were highly unlikely in an endothermic
sauropod. Accessory hearts or a siphon mechanism, with
sub-atmospheric blood pressures in the head, were also
not feasible. If the blood flow requirements of
sauropods were typical of ectotherms, the
left-ventricular blood volume and mass would have been
smaller; nevertheless, the heart would have suffered
the serious mechanical disadvantage of thick walls. It
is doubtful that any large sauropod could have raised
its neck vertically and endured high arterial blood
pressure, and it certainly could not if it had high
metabolic rates characteristic of endotherms. 
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Guy Leahy


--- Sim Koning <simkoning@msn.com> wrote:

> The problem of high blood pressure is a major
> problem for those who believe 
> that sauropods could elevate their head at heights
> far greater than their 
> heart. Could their carotid arteries have evolved
> into peristaltic pumps? For 
> those of you who don't know what peristalsis is, its
> the process that moves 
> food and liquid through your esophagus and
> intestines. Arterial walls have a 
> layer of smooth muscle tissue that may have evolved
> to work as peristaltic 
> pumps to push blood to the brain. If this was the
> case, wouldn't it allow 
> sauropods to have highly elevated necks without the
> need for extremely high 
> blood pressure?