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Re: Fw: [GSP1954@aol.com: MORE DINOSAUR ENERGETICS]



In article <199612191736.MAA06628@juliet.ucs.indiana.edu>, Van and Kathy
Smith <vksmith@dwx.com> writes

>Here is Mr. T. Jones' response to my message.
>>Terry D. Jones wrote:
[snip]
> 
>No--RTs ARE causally and functionally linked to endothermy unlike
>erect limb posture, etc.  W. J. Hillenius has already shown that if
>you bypass the RTs in a mammal, the amount of respiratory water loss
>would through the daily water flux out of balance.  Current work in
>our lab show the same for birds.

This is certainly not true for at least one mammal - human. Average adult
human breaths about 10,000 litres of air a day which is moistened by about
750 ml of water. Of that only about 150 ml is saved and the rest (80%) is lost
in the exhaled air (normal turnover of water in humans is >3 litres/day).
Turbinectomy (surgical removal of the inferior turbinates) does not alter water
balance to any significant extent. Total turbinectomy may cause drying of the
nasal mucosa above the point of the attachment of the inferior turbinate
because of the direct exposure to dry air, but no changes occur in the
respiratory system otherwise. Turbinates are not the only structure that warm
and moisten air; septal mucosa (specially the Little's area which has surface
features very similar to the inferior surface of the inferior turbinate, 
including
the so-called blood lakes) is as good as the inferior turbinate which is the 
only
turbinate relevant for these purposes (in humans).

H.sapiens (terrestrial bipedal endotherm) have smaller (reduced) turbinates
compared to the majority of the mammals and birds and possibly even do
without it. Why not the dinosaurs ?

Another point (again in humans, I am sorry - this is the only animal I am
familiar with) - the narrowest part of the respiratory tract is not the nasal
passages, but the trachea. No much point in widening the nasal passages if
another part of the tract is even narrower. Has anyone compared the tracheal
cross-section to the size of the nasal passages in the extant endotherms and
ectotherms and between them ? Do we have any estimate of the size of the
trachea of the dinosaurs to compare with the nasal passages ? How about
the birds ?

Gautam Majumdar 
gautam@majumdar.demon.co.uk