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Re: Rearing up on hind legs
Following up on Sherry Michael's mention of _Brachiosaurus_...
_Brachiosaurus_ certainly appears to have been adapted as a high browser, what
with its elongate forelimbs and high shoulders. Even a modest reconstruction
of the brachiosaur neck, which would position the cervical vertebrae in a
direct line with the dorsal vertebrae, would result in a very high neutral
position for the head, and it is likely that it could have reared somewhat
higher, as required. If the animal is to avoid dehydration, it must also be
able to drink at ground level. Even if the forelimbs can collapse to bring the
chest to the ground, the neck must be able to reach up and down quite a bit!
Therefore, we can suppose that -- however they did it -- some sauropods must
have been able to move their heads from a position below the level of the heart
to a position which is very, very far above that level. If such a feat should
have been a regular habit among camarasaurs, why should it be inconceivable for
diplodocids to control their blood flow when rearing up? Is there fossil
evidence of fainting sauropods or sauropods whose heads exploded when they
attempted to drink? I offer no answers to the problem of blood flow, but
consider this: sauropods are so far off the charts in so many respects from
extant animals, and yet they thrived for a time. I do not expect sauropods to
conform to the apparent rules of living animals; their anatomy bespeaks of
considerable evolutionary novelty. Perhaps they featured innovations we can
only dream of.
-- Ralph W. Miller III email@example.com