Re: Sauropod Energetics (Peristaltic pump)

[dinoboygraphics@aol.com]

> > > 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

www.skeletaldrawing.com

-----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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