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At 11:14 PM 7/23/98 EDT, GSP1954@aol.com wrote:
>Varner's statement that it surely was energetically more expensive for
>Diplodocus to rear up than to breath down its hyperlong trachea is
>unsubstantiated. Rearing was merely a matter of briefly using some muscles to
>control body posture during rearing, gravity via the mass of the tail did
>of the work, once reared up the cost was no higher than standing on four
>The cost of overcoming the enormous dead space of the trachea occurred with
>every breath, a few times a minute. 
>Conifers are actually high in calories, and the energy to be gained from a
>mouthfuls easily makes up for the energy needed to walk a few extra meters to
>reach food with a short neck. 

This would depend on how large their lungs were wouldn't it?  Could they
have gone without breath long enough to rear up and snack?  Along this
it seems that they will necessarily be rebreathing all the air in their
necks with every breath after an exhale.  It seems rather inefficient, but
must have worked.  Are their lungs so large that this constitues a small
percentage?  Perhaps their exhaled breath had a high percentage of oxygen?