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Re: sauropod lung collapse



The main point is that the inability to use the neck as a snorkle in no way 
excludes semi-aquatic lifestyle from the list of plausible sauropod lifestyle 
choices. It is known that relative to metabolism, dive-time scales positively 
to mass. If a 1 ton croc can hold it's breath for 30-45 minutes, then a large 
sauropod might plausibly have gone much longer than an hour on stored O2.

Also, their ability to store and conserve O2 may have allowed them to deflate 
their lungs prior to submerging, reducing bouyancy to the point that walking on 
the bottom was practical.

Don

----- Original Message ----
From: Phil Bigelow <bigelowp@juno.com>
To: dinosaur@usc.edu
Sent: Tuesday, January 10, 2006 7:57:00 PM
Subject: Re: sauropod lung collapse

How do we know that lung collapse in submersed sauropods would be a "bad
thing"?

Consider the size of the typical sauropod's brain.  Very small, probably
mainly brain stem and limbic system, with the remainder mostly what we
would consider "lower brain function" in mammals (eat; mate, fight,
flee).  This implies low oxygen requirements compared to the
oxygen-hungry requirements of a mammal's huge frontal cortex.

During deep diving, the lungs of seals and sea lions are totally
collapsed.  Which is normal.  They evolved that way.

Would sauropods need to breathe while wading/swimming or during aquatic
feeding?  A half-hour to one hour without taking a breath is not
completely out of the realm of possibility.  How much spare oxygen was
stockpiled in the tissue of sauropods?

One last question:  Do penguin lungs collapse during dives?  What role
does their air sacs play during diving?

<pb>
--

On Tue, 10 Jan 2006 15:27:39 -0800 (PST) "Jaime A. Headden"
<qilongia@yahoo.com> writes:
> W. F. Zimmerman (wfz@wfzimmerman.com) wrote:
> 
> <This doesn't clinch the case, does it?   Plenty of large animals 
> like
> hippopotamuses and, yes, whales manage to spend quite a bit of time 
> deep under
> water without having collapsed lungs and do their breathing when 
> they're safely
> above water.>
> 
>   As well as crocs, sirenians, etc.
> 
>   A decent test may be to study the morphology of the ribs for 
> continuous
> submersers like aquatic species like sirenians and dolphins versus 
> those of
> temporary submersers like hippos and crocs, and rare submersers like 
> horses,
> etc., and determine the variabilities. The presence of dense bone to 
> counteract
> bouyancy, rounded ribs to counter external pressure, a round 
> thoracic cavity
> rather than "slab-sided" for equalization of pressure around the rib 
> case, etc.
> 
> 
>   Since we are having difficulty reconstructing the actual breathing 
> system in
> sauropods due to some interesting consdiderations of the involvement 
> of the
> pneumatic system of the vertebrae from the sacrum up to the anterior 
> neck, we
> may have to use only the skeletal features present and their 
> capacity to infer
> soft-tissue, and compare these to sauropods. But as Alexander noted, 
> the limb
> system of sauropods appears to be terrestrial based, and is adapted 
> to bearing
> heavy loads vertically, rather than semi-sprawled, such as one might 
> expect if
> the animal were walking around with its full weight on its feet, 
> also perhaps
> without any mitigating effects like bouyancy in water, etc.
> 
>   Cheers,
> 
> Jaime A. Headden
> 
> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
> 
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