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RE: Mammals are not dinosaurs



On Wed, 4 Dec 1996, Robert J Meyerson wrote:

> Hogwash!  If what you say is true, how does one explain the chasmosaurines
>  tendancy for large fenestra in their frills?  How else does one explain the
>  holes in the skull which lead from the lower jaw to the fenestra?  The only
>  plausible explanation is that the frills are attachment sites for the jaw
>  muscles.

        An obvious possibility is that the frill was a display 
structure, and that evolving a couple of big holes in the thing lightened 
the head, reducing both weight and excess bone tissue. The fenestrae 
could just be covered over with skin. Simply economy.
        Also, your explanation fails to account for the 
 *absence* of said fenestra in Triceratops. If they were there for 
chewing, how could Triceratops just eliminate them? If, however, they 
were there only for decoration, a little selective pressure from highly 
combative members of the same species, or the bone-crushing ability of T. 
rex, might well select against fenestra and for heavy armor.
        If you don't buy the neck armor thing, take a look at one of the 
Mongolian ankylosaurs. The damn thing has reduced its eight plates of 
neck armor down to two *massive*, fused bone collars. Perhaps T. rex and 
bataar did, so to speak, go for the jugular. 

        Nick Longrich