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[sauropod@berkeley.edu: Re: [mhabib5@jhmi.edu: Re: sauropod lung collapse]]

Forwarded for Matt Wedel.

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Date: Wed, 11 Jan 2006 02:45:32 -0800
From: Matt Wedel <sauropod@berkeley.edu>
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To: Mike Taylor <mike@miketaylor.org.uk>
Subject: Re: [mhabib5@jhmi.edu: Re: sauropod lung collapse]
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> Some familiar issues here, but I do find myself intrigued by the
> following issue: when a sauropod waded into deep water -- as deep as
> it could while still being able to breathe -- to what extent could
> its air-sac system collapse?  And how much would this affect the
> bouyancy models of Henderson who IIRC did not mention having taken
> this into account?

I believe diving birds exhale as much as they can before they go down. I 
think they probably have to, otherwise they wouldn't _go_ down. The 
lungs themselves are not collapsible--or rather, they are, but lung 
collapse is fatal, because the air capillaries are so small in diameter 
that once they collapse, surface tension is sufficient to keep them that 
way. Ornithologists exploit this in the field: you can euthanize a small 
bird by pinching its chest.

Since you're restricting this to "as deep as it could go and still 
breathe", the answer with regard to air sacs sensu stricto is that they 
couldn't collapse much; they have to inflate to drive air through the 
lungs (and receive it on either end).

And, of course, the air in the bones can't come out. Keep in mind that 
the volume of air in the bones alone in Diplodocus was about 10% of its 
body volume, and that's with me taking the conservative turn at every 
fork in the road. Our lungs are about 8-10% of our volume, and we can't 
just walk on the bottom until the water is over our heads. Unless we're 
weighted, we float, and sauropods would have, too--even with their air 
sacs emptied out.

If you think these points would be of interest, feel free to forward 
them on. And thanks for keeping me posted on this most interesting 

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