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Re: sauropod rearing



Greg Paul (GSP1954@aol.com) wrote:

<Posterior dorsals are smaller than anterior ones, a classic quadrupedal
adaptation. 

In fact, posterior dorsals are quite small. This is because they rarely need
bear the load of the entire body while it is being held by only the hindlegs.

When elephants rear they flex the knees strongly. The pelvic muscles probably
cannot properly function when the hios are tilted up and I don't think
elephants can walk on two legs, but I'm not entirely sure because I cannot
entirely recall what circus elephants are capable of.>

  This is, I think, the number one feature that seems to have been ascribed to
sauropod rearing, that elephants can do it. However, as I understand it,
elephants rear by bringing the center of gravity above and backward of the
pivot point, that is, the foot, and thus push upward. They have robust
hindlimbs, regardless of the robusticity of the forelimbs, and broadly splayed
anterior ilia which help support the weight. Note however, that elephants need
only support a few tonnes on their hips, sauropods exponents more. So the
obvious testing factor, aside from the caveat of ascribing sporadic behavior to
fossil animals, is to determine the bone strength and muscle size of the
relevant rearing muscles in animals that rear. I am not sure anyone has done an
electromyographic study of elephant to determine which muscles are being used,
and also a test of the bone strength, but it would be interesting if someone
did some primary testing on this issue.

  It should also be tested whether sauropods can easily support a given mass on
their tails, as a tripod, or whether the tail can sufficiently dorsiflex to
accomodate this speculative posture. We should also consider the problems of
what happens as the sauropod _comes down_, including blood pressure, fluid
movement, and concussive force as the animal hits the ground. Even elephants
make a thump when coming down, but then, they are a lot smaller than most
sauropods.

  I would hazard a guess that people are finding the elephant/sauropod
analogies more romantic than any serious scientific research might show. They
have, for example, ignored closer analogues to elephants in terms of
proportions, size, weight, and body stature: ceratopsians. These rearing
principles GSP offers could more easily be found in ceratopsians, while
sauropod anatomy, with their larger posterior dorsals, massive cantilevering
spinous processes, and various other adaptations for a horizontal posture,
seems grossly divergent from anything elephantine.

  Just a thought.

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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