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Re: _Parasaurolophus'_ crest and how much we can't deduce from it.



On Sat, 9 Mar 1996, Nicholas R. Longrich wrote:

>       if Parasaurlophus was trying to conserve water through 
> condensation, the purpose of the nasal passages would be to increase 
> surface area, right? But it's an incredibly inefficient way to do that. A 
> much better way is to use thin, highly folded sheets of bone, if you want 
> to increase surface areas (is this what the whole respiratory turbinate 
> thing is about?). Parasaurolophus does have a lot of nasal surface area, 
> but it's a really wasteful way to get it. I have no idea what the 
> original purpose of duckbill nasals are, but in Parasaurolophus, the 
> purpose of the crest is to increase the length, not surface area, of the 
> nasal passages. 
> 
>       -nick L.


We have established for a fact, then, that the mucosa lining these nasal 
passages were as smooth and flat as the tubes themselves?  And that all 
living structures represent the most efficient solutions to the 
engineering problems they address?

There are blood vessels in the heads of some mammals proximate to 
breathing passages; these blood vessels pass heat to the air in the 
passages in order that the brain remain cooler.  If, as we're told, 
Parasaurolophus had a flap of skin stretching from crest to nape of neck, 
might this flap have been highly vascularized as well, exposing much 
blood over a broad surface to the air, carrying heat from the crest?  I 
don't know, but I doubt the long nasal passages sprung forth full-formed 
like Athena from the brow of Zeus (or whatever) in order merely to make 
noise.  I think the tracheae of these extraordinary beasts would have 
been more than sufficient.  

But I simply don't KNOW.  I remember in the old days when they said with 
similar assurance that the crests in these animals served to "store extra 
air when the animals submerged in their watery homes."

Uh - oh.  
Thanks.
John McLoughlin