Re: Forster's papers on Triceratops

["Tim Williams" <T.Williams@cclru.randwick.unsw.edu.au>]

Stan Friesen wrote:

> Based on Geroge Olshevsky's report, it appears as if she rejected
> sexual dimoprphisms for T. horridus/prorsus because _T. horridus_
> is much more common.

This rationale has also been used to differentiate two _Allosaurus_ 
species in the Morrison.  There are two morphs (of equal 
stratigraphic age), one more robust than the other, but one (and I 
can't remember which) predominates overwhelmingly in the Cleveland-
Lloyd Quarry. 

Either there were two sympatric species (or two genera according to 
Bob Bakker, the last I heard) or them male allosaurs in Utah had one 
doozy of a harem.  :-)  Greg Paul's _PDW_ has a nice analogy for 
this kind of dilemma using his "leopards and lions" scenario.

> I do not think this is conclusive, at least if _T. horridus_ is
> the female morph.  In an animal with a harem type herding system
> females may well be substantially more common than males.  I am far
> more inclined to this view than to the idea of two such similar
> species being sympatric. 

Don't forget about about the third one - _Diceratops hatcheri_.  
IMHO it would also qualify as a sympatric species.