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Re: Sauropod Energetics (Peristaltic pumps for arteries?)



One problem with the peristaltic idea is that this
type of muscular contraction is restricted to the
digestive tract in vertebrates, and nothing like it is
known for the vascular system for any extant
vertebrate. One would have to postulate that sauropods
evolved a structure not known to occur in any living
animal, including taxa which are known to have
elevated blood pressures.  An additional problem is
that this idea isn't testable. As I'd noted in another
post, if Kent's reconstructions are correct,
cardiovascular adaptations seen in living mammals and
birds would work quite well in sauropods, without the
need to postulate mechanisms for which there are no
known extant examples... :-)

Guy Leahy

--- dinoboygraphics@aol.com wrote:

> 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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