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Re: RTs (lengthy)



 Michael Teuton wrote:
> Maximum ventilatory capacity (MVC) is 
> a function of the entire ventilatory apparatus.  Not just trachea 
> size.  I do not know if cross sectional measurements of tracheae 
> across classes are going to tell us anything.  MVC under exercise or 
> demand is going to be dependent on a number of factors within a 
> species and even for different classes of animals.

Agreed.  My point was made mainly to counter Mr. Jones's -- if his
argument has merit then perhaps the most important place to 
measure would be the narrowest part of the main air passageway.  I'm
still very anxious to see the results of his latest study -- Mr. Jones
replied to my original message saying that it looks like there _is_ a 
correspondence between tracheal cross sections and energetics 
among modern animals.

>
>Are advanced maxilloturbinals necessary for high O2 consumption or 
> has the multifunctional turbinates evolved independently in birds and 
> mammals as an adjunct to high ventilation rates as well as their 
> other functions?  Are they primarily for warming  inflowing air, 
> trapping particles, fighting disease,  catching some water 
> vapor on exhalation and not allowing high ventilation rates to 
> dessicate the mucosa?  If the ancesters of mammals had turbinates 
> would it surprise us that most mammals had them?
>

I believe Mr. Jones argues that without RTs, an animal on an expensive
energy budget would lose so much H20 and heat as to render that animal
incapable of moderating either.  I suspect that RTs exist in both 
modern mammals and birds because, for small forms (and all modern 
mammals and birds evolved from very small ancestors), they are indeed 
important for heat and moisture retention (ventilation surface area/body
volume
as well as ventilation rates both become higher and higher for smaller and 
smaller animals).
 

> Do you think that dinosaurs had the ability to shunt warmer core 
> blood to the skin and cooler extremities as an additional way to cool 
> themselves?  
> 

Yes, particularly in elongated examples like sauropods, as well as
stegosaurs, 
and, of course, sail-backed dinosaurs (among others).

V.