Re: again: frill of Triceratops

[Jeffrey Martz <martz@holly.ColoState.EDU>]

Aravind wrote:

> process of reinforcement. Initially it evolved  due to sexual selection. 
> Subsequently it gave a an oppurtunity for jaw muscle attachment and again 
> it was reinforced by sexual selection. 

    Enlarging parietals would be providing larger muscle attachment areas 
before they started looking especially big and sexy.

> times in evolution like the Austropithecus. robustus cranial crest. I 

     The R.robustus cranial crest would not even have been visible with 
the temporal chewing muscles in place, any more than you can make out the 
sagittal crest on a gorilla's skull in a fleshed out animal.
      I think it is time for someone especially knowledgeable on the 
subject to give the complete run down on respiratory turbinals.  I know 
this subject pops up on this list a lot, but some of the comments that 
have been made about the SCIENCE paper seem to show misunderstanding of the 
purpose RTs serve in endotherms.
     I might also add that as far as I know, the vast majority of 
vertebrate tetrapods habitually breathe through thier noses except 
during those relatively rare times when they have been doing serious 
exerting.  Begging off small nasal passages in dinosaurs by saying they 
all might have walked around breathing through thier mouths seems like a 
pretty poor dodge.  Sort of like saying pterosaurs could have been fully 
terrestrial if they walked around all the time with thier wings folded 
up.  

LN Jeff
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