Re: Complexity of the Oviraptoridae

[Darryl Jones <dinoguy@sympatico.ca>]

At 11:53 PM 7/13/2001, qilongia@yahoo.com wrote:
>   This is meant as a short-form discussion of the two recent
> theropod dinosaurs assigned to the oviraptorids, *Khaan
> mckennai* and *Ciripati osmolskae.* In addition to these taxa,
> there are still several other specimens out there of some
> questionable identity, but are distinct nonetheless. These are
> not the last of the oviraptorids you'll hear from.

There seems to be a tremendous diversity of these suckers.  I am wondering
if there are specimens being named that aren't just variations of one
single species.  There are 4 genera of very similar animals known from the
Djadokhta alone.  I am not claiming supreme knowledge of this, but this
seems high to me.  How could such similar animals evolve side by side in
the same area?

>   Within the Oviraptoridae, there is a distinct set of
> morphologies, easily described by the three principle taxa:
> ingeniine, for those with very short hands, arms;
> conchoraptorine for those with intermediately elongate hands,
> but a third finger shorter than the second and closer to the
> pollex in size, and a moderately pneumatic skull, as well as a
> premaxilla with very large denticles; oviraptorine, for those
> with very elongated hands and a cranial crest that extends
> caudally to the rear of the skull (sagittal crest). Using this
> criteria, *Khaan* is a conchoraptorine for the most part, as
> suggested by Norell et al., 2001, and *Ciripati* is closer to
> oviraptorines, but still appears to be conchoraptorine, as is GI
> 100/42.

Could some of these differences be chalked up to individual
variation?  Ontogeny?  Sexual dimorphism?  Is this another case of seeing
specimens evolve as the sediment is laid down?  We are starting to get
thinner when it comes to numbers of specimens belonging to each
genus.  Mickey Mortimer said "Now that it's referred to Citipati (possibly
my least favorite dinosaur name....), O. philoceratops is only based on the
holotype AMNH 6517."  Could it be possible that the type specimen is
preserved poorly enough that we have gone too far in naming new specimens?

>   Relationships:
>
>   *Khaan* resembles *Ingenia* is having a relatively short arm,
> a nearly strait ischium along the caudal/dorsal surface, a
> robust metatarsus, and short second and third manal digits. It
> resembles *Conchoraptor* in the degree of pneumatization of the
> skull, the dorsally expanded nasals, the general form of the
> lower jaw including a short triangular instead of prong-shaped
> invading process of the surangular into the external mandibular
> fenestra. It is generally a primitive oviraptorid, though more
> derived and similar to *Oviraptor* than to *Ingenia.* Generally,
> this animal, based on the hand, form of the cranium and degree
> of pneumatization, resembles *Conchoraptor,* and this may
> indicate a monophyletic group. *Ciripati,* *Oviraptor,* *Khaan,*
> GI 100/42, and *Conchoraptor* all share extensively pneumatized
> cranial bones, whereas *Ciripati* shares with *Oviraptor* and GI
> 100/42 the dorsally expanded nasal pneumatic chambers, extensive
> premaxillary pneumatization, a premaxillary sagittal crest, and
> also share a tear-shaped external nares, narrowest caudally, but
> the short axis is much larger than in other oviraptorids.
> *Ciripati* and *O. mongoliensis* have similar humeri, with the
> proximal margin of the deltopectoral crest arising to the level
> of the humeral head, but similar to GI 100/42 in the general
> form of the shaft, which bears a mediocaudally inflected head
> and cranial inflected distal condyles, but a generally strait
> shaft. *Ciripati* seems to be closer to *Oviraptor* than to
> *Conchoraptor* or *Ingenia,* and is thus an oviraptorine

Is it just me, or do they all seem to be similar to each other in some
way?  This was what made me wonder it there was not more at play here than
different genera.

I'm just beating a dead horse here, aren't I? :-)



Darryl Jones  <dinoguy@sympatico.ca>

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