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Re: DINOSAUR digest 3445




--- dinosaur@usc.edu wrote:

>   2) RE: sauropod lung collapse

I think most sauropods were terrestial. But
theoretically some could be semi-aquatic like hippos.
They would swim and dive, feed underwater and
resurface to breathe holding neck horizontaly and back
above water. Nothing in physics prevents it. 

Old theory that sauropod couldn't breathe underwater
is based on old interpretation: sauropod was much
heavier than water, walked on bottom, didn't swim,
raised neck vertically as snorkel.

That old scientist overlooked one thing. All living
animals have density around that of water. So even
heaviest animals become weightless and can swim well
(unless have armor, which sauropods lacked). Hippos
and elephants are good swimmers. 

One question is how close sauropod density was that to
water. This is too fine to discover experimentally,
because needs knowing exact relative amount of
muscles, fat, bones, lungs and we only know bones.

Even if typical sauropod was a little heavier than
water, evolving buyoance was easy. Fat and air sacs
are lighter than water. Average sauropod could
actually be lighter than water and have trouble with
diving, not with breathing on the surface.  

Interestingly, the same physics allows us to restore
behavior of extinct marine reptiles. Long-necked
plesiosaur must have gone to the surface with body and
neck almost horizontal. Only then it could breathe.  

Same applies to short-necked plesiosaur, ichtyosaur,
whale and every big, air-breathing animal underwater.
If famous Loch Ness monster existed, it too must have
swim horizontally just below the surface of the lake
every time it needed a breath. Scottish tourists would
quickly see humps on its back and mystery would be
quickly solved. ;)

Jerzy Dyczkowski


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