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Re: Sauropod Energetics (Peristaltic pump)

Sauropod discussion frequently uses the elephant as an analog for rearing, and the giraffe as an analog for the neck. But the sauropod bipedality story will be far more difficult to resolve than the sauropod neck story (which "only" involves osteology and a reasonable, non-naive estimation of cartilage, at least to reconstruct an undeflected neck).

Now we'll need to quantitatively estimate muscle moments, the center of mass for the portion of the skeleton that is engaged in pivoting about the acetabular axis, the starting and ending poses, and more.

But since it seems so hard to get simple skeletal reconstructions straight (sorry) for sauropods, it looks fun-but-nearly-hopeless to make headway on their rearing up.

Would anyone want to help lay out some ground rules on what would be a convincing (if not overwhelming) argument either for choosing between the two (mutually exclusive) alternatives:

1) that (at least SOME) adult sauropods engaged in feeding bipedally (or tripodally)

or alternatively:

2) NO adult sauropods engaged in bipedal (or tripodal) feeding.

My question is not which is your answer (1 versus 2) but what would be a convincing argument for nailing either alternative.

To be constructive, let's please separate the problem into biomechanics (which is testable for a range of bracketed estimates) and the neural command-and-control coordination issue (which I suspect will be far more difficult to resolve).

[Regarding the vestibular coordination issue, ever walk while carrying an extended extension ladder vertically, like when you are painting a house, and you want to move the ladder around the corner? As the upper end of the ladder sways about its up to you to correct it before its too late. In this case you're on the ground looking up, and you've got a big clever head on your shoulders. In the sauropod's case, its itty bitty head is way up there, trying to reach something to eat while suspended at the end of a dynamically flexing neck that's extended above a swaying trunk supported by perhaps somewhat wobbly legs on uneven ground, and it's got to decide in real time whether the current degree of swaying that feels and sees is within tolerance, or whether its time to take a sidestep, or ...]


[Oh, and rearing up for mating is just not the same problem (as we all know). Sauropods could rear up to mate as if partaking in a bit of mountain climbing, engaging the pollex claw as a crampon, and anyway the entire weight of the male need not be maintained in static equilibrium during the mounting. For a sauropod (or an elephant for that matter) to sustain a bipedal posture for even a few seconds is significantly more demanding, and all for a lot less gain, seemingly.]