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Re: PACHYRHINOSAUR LINEAGE



From: Jeffrey Martz <martz@holly.ColoState.EDU>
 > Achelousaurus has the big bosses over the nose and orbits reminiscent of 
 > Pachyrhinosaurus.

Close enough, in fact, that placing it in a separate genus does not
seem justified to me.

 >      So: Achelousaurus is tied to Pachyrhinosaurus by the bosses, and 
 > Einiosaurus is tied to Achelousaurus by the fact that both genera only have 
 > two 
 > spikes on the frill.  

I am not sure how relaiable this character is for indicating phylogeny.
It (and most other frill-related characters) are almost certainly
intraspecific display structures. Such structures are subject to
extremely rapid, and divergent, evolution during speciation.

In fact, given that the cladograms in the paper defining these genera
based almost entirely upon frill and horn characters, I am not sure
how much reliance can be placed on them.

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.