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Re: Sauropod Energetics (Peristaltic pump)



That's Bakker's hypothesis, but I don't know how long even a small
brain could function without a constant oxygen supply. It would mean that these animals would have to rear up, eat for a few minutes, go back down and repeat. Would this practice burn more calories than what it actually got from the tree? It makes me wonder if this "working out while eating" strategy would be worth it. <<<

I agree that Bakker is speculating here without any real data, but as for the question about energetics, this stems from a common misconception about locomotion and feeding; locomotion is really quite cheap, and it get's cheaper (as a relative proportion of an animals daily energy budget) the larger you get. Elephants routinely rear up to feed off of single branches, despite smaller size and poorer osteological adpatation for such a behavior. Larger sauropods rearing for a minute or two (multiple bites) would be well in the black energetically.

There are no modern 10-30 ton herbivores with bird necks and far better leverage for rearing than elephants alive today; it isn't that unreasonable to infer that they were able to supercede extant mammals in their cardiovascular abilities re: getting blood to their brains at higher elevation. Especially since dinosaur descendants (birds) themselves have a superior cardiovascular ability.


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

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-----Original Message-----
From: Sim Koning <simkoning@msn.com>
To: dinosaur@usc.edu
Sent: Thu, 26 Jan 2006 08:49:54 -0500
Subject: Re: Sauropod Energetics (Peristaltic pump)

Would some sauropods need to maintain blood flow in order to raise
their 
heads long enough to take a mouthful? Surely if a diplodocid (or other 
species that maintained horizontal necks most of the time) was able to 
seal off the blood supply out of the neck for a few seconds to prevent 
blood from draining away from the brain, then a few moments of no
blood 
flow to that tiny brain wouldn't be so critical? 
 
It would mean they couldn't raise their heads for any length of time 
(barring other unknown blood flow mechanisms), but it wouldn't make 
quick forays into higher elevations entirely impossible. 
 
That's Bakker's hypothesis, but I don't know how long even a small brain could function without a constant oxygen supply. It would mean that these animals would have to rear up, eat for a few minutes, go back down and repeat. Would this practice burn more calories than what it actually got from the tree? It makes me wonder if this "working out while eating" strategy would be worth it. 
 
One problem with the peristaltic idea is that this type of muscular 
contraction is restricted to the digestive tract in vertebrates 
 
Peristalsis is also used for oviducts, ureters and other tube-like organs. 
 
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 
 
Annelids (worms) use peristalsis to pump blood through their circulatory system. This type of system is the most primitive form of closed circulation and was probably the system that the ancestors of all vertebrates used before developing a centralized heart. It should also be noted that the arterial walls still retain muscle tissue and that the heart was probably derived from earlier peristaltic systems. 
Sauropods, in my opinion, could have easily evolved such simple system again. 
 
An additional 
problem is that this idea isn't testable. 
 
Neither is the notion that they had a giraffe like system 
 
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... :-) 
 
It still doesn't explain how sauropods could rear straight up and not lose consciousness. With all the examples I've given, I don't understand why this is being taken as such a far fetched idea. 
 
The last point (#5) is a bone of contention. Some silhouette drawings
>suggest sauropod necks >that naturally curve upwards, but under scrutiny, >those silhouette drawings show subtle-but->cumulative geometric >inaccuracies, and anyway, apparently at least some such illustrations are >not >even intended to depict the ONP. 
 
Kent, While I agree the the ONP was probably horizontal with most, if not all sauropods, is there any way to reliably put a limit on their flexibility? Human contortionists can bend their spine to an incredible degree without any ill effects, is it possible sauropods could do the same with their necks in some cases? I also think sauropods are much more analogous with elephants. I've always viewed the long neck as serving the same function as the trunk of an elephant, an organ that allows sauropods to browse low and high with equal efficiency. 
 
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