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Re: Horner's Pachy Lumpin' - Your Thoughts?

--- On Sun, 1/10/10, Thomas R. Holtz, Jr. <tholtz@umd.edu> wrote:

> Another ceratopsid case of metaplasia: the postorbital and
> nasal horns of
> young Pachyrhinosaurus are indeed horns, but as they aged
> the postorbital
> horns get resorbed and remodeled into pits and the nose
> horn into the
> distinctive mound.

Is it known where the "unicorn-style" horn shown in the wikipedia article 
enters the sequence? Is this a case of 'lose-two, gain-one' post-orbitals, or 
'have-three, lose-two'? Or something else entirely?