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Re: Pachycephalosaurs



Hi all, Although I am still off dinonet, Mickey still forwards an 
occassional message to me. 

Regarding Ralph's comments on pachy's:

>. Those who have argued vehemently against head
>  butting in pachys tend to visualize a very end-member version of it 

I am not clear where Stegoceras and Pachycephalosaurus fall in Ralph's 
scheme, but, yes I argue against their head butting.

> You can head butt from a few inches away and get your
>  point across and not worry about "dangerous glancing blows", etc. 
>That especially goes for Pachycephalosaurus with the flatter dome 
>(relatively shaped) but should work for most.

Sorry, but I disagree.  The cross section of the dome (i.e. 
pachycephalosaurids) is arced so that an exact point to point impact is 
almost impossible.  Big Horn sheep (the usual model) have an impact 
plateform developed by the horns.  Spalling of the horn sheath show 
where impacts occur and this area is flat.  With the horns spirally 
posteriorly, a functionally broad impact plateform is developed.  That 
alleged for pachy's is non-exsistant, except in the flat headed forms.


> I think that the dome fits the sexual model better - that's why they 
>have the best documented sexual dimorphism in the dinos -

I suspect Peter Dodson would challenge this bold statement, 
nevertheless, it is true that the record for Stegoceras is good, but I 
am less convinced that is true for Pachycephalosaurus, Stygimoloch and 
Homalocephale. Yet to be resolved is the possibility that 
Pachycephalosaurus and Stygimoloch are sexual dimorphs of the same 
beast.  We'll have to await Dale Russell's analysis of the new Triebold 
specimen.  By the way, ahem, Ralph, I leave for the Triebold camp at 
the end of August to be camp cook, thereby honoring the lost bet.  I'll 
be glad to deliever your beer cooler to him.

>  That's my nickle's worth, let the games begin.

See above.  I leave for the field in a couple of hours, so won't be 
able to respond to any of Ralph rebuttals for two weeks.