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Re: Sauropod Energetics (Peristaltic pumps for arteries?)



I read the article that Guy posted too; I was not impressed that they'd been terribly exhastive in assessing ways to acomplish elevating blood up the neck, but more imortantly, this is only a big problem if you think speculative interpretations of unpreserved soft tissue should out weigh the osteological evidence. Now, if Kent Stevens is right, then there is no problem at all. If he isn't (and I supsect we'll be seeing more on this in the future), then the problem is trying to infer what soft-tissue adaptations were employed, not saying the osteological signal is decieving us because we can't easily figure out the soft-tissue solution.

Nature does not evolve things it can't use (although some times she holds on to things after they have ceased to be useful), so the issue continues to be whether or not the osteological morphology supports some sauropods having habitually high necks and/or reared on a regular basis.

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com

-----Original Message-----
From: Sim Koning <simkoning@msn.com>
To: dinosaur@usc.edu
Sent: Wed, 25 Jan 2006 13:11:41 -0500
Subject: Re: Sauropod Energetics (Peristaltic pumps for arteries?)

I read that article before writing my post. The article only mentions accessory hearts or a siphon mechanism, both of which I agree would not work. Peristalsis is not the same as having accessory hearts, nor does it work like a siphon. Peristalsis is what allows you to drink a large glass of beer while standing on your head. Since this type of pump has evolved for other parts of the body, I don't think it would be a stretch to imagine the muscle tissue that already exists in arteries to evolve in such a way. The following are links on the subject. 
 
http://en.wikipedia.org/wiki/Peristaltic_action ;
 
http://en.wikipedia.org/wiki/Peristaltic_pump ;
 
From: Guy Leahy <xrciseguy@sbcglobal.net> 
To: simkoning@msn.com 
CC: dinosaur@usc.edu 
Subject: Re: Sauropod Energetics (Peristaltic pumps for arteries?) 
Date: Wed, 25 Jan 2006 09:33:08 -0800 (PST) 
 
The following article discusses why such a solution to 
high blood pressures in rearing sauropods is unlikely: 
---------------------------------------------------------------- 
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. 
----------------------------------------------------------------- 
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? 
 
 
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