Oviraptor skulls

[Matthew Donald Celeskey <mc7b+@andrew.cmu.edu>]

Hi -> 

Here's a quick question I was hoping someone could help me out with:

I've noticed that the reconstruction of the Oviraptor's cranial features
have changed over the years - in the earliest illustrations I've seen,
the head is quite ornithomimid - no sign of a crest at all.  In later
(mid 80's) illustrations, such as Norman's Encyclopedia of Dinosaurs and
I think Paul's Predatory Dinosaurs, the Oviraptor is shown with a strong
beak, and a small hooklike projection or horn above the nose. It is
accompanied by an illustration of the skull, which looks as if the tip
of the premaxilla is missing and the nasal projection is evident. 
Finally, in more recent restorations, such as Lambert's The Ultimate
Dinosaur Book and Weishampel's The Dinosauria, there is no sign of the
nasal projections, all oviraptorids have either large, rounded or peaked
crests, or no cranial decoration at all.

Now, I understand that the head was crushed in the type specimen of
O.philoceratops, and that its toothless jaws prompted an
Ornithomimus-type reconstruction.  My question is this -> is the "middle
period" Oviraptor (with the small nasal horn) at all valid (e.g.: as a
different species or example of sexual dimorphism), or is it a
reconstruction based on the initial fragmentary material, now discarded
due to more recent, better-preserved finds?

If anyone would know the answer, or at least point me to a source where
I might find it (I've checked all the ones I've listed), I would be
appreciative.

Thanks
Matt.
mc7b@andrew.cmu.edu