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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
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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