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Re: David's Statements [Extended Version]



Jaime Headden wrote-

>   This is confusing, because the nature of the coronoid in
> oviraptorids has only been once mentioned in an abstract, and
> this has been restricted to a skull that forms a new genus (not
> *Oviraptor philoceratops*).

To be fair, the oviraptorid coronoid was mentioned in an actual paper too
(Here would be a great place to put the reference, but for the life of me, I
just can't find it :-( . I know I knew about oviraptorid coronoids before
the SVP 2000 abstract though).

> The same may be true of
> ornithomimids, but then, I have mostly *Gallimimus* to work
> from, and Osmólska, Roniewicz, and Barsbold, 1982 state that
> this genus most certainly had a coronoid, illustrated as
> situating low on the jaw and posterior to the ascending process
> of the prearticular. Now, perhaps someone in Sacramento can look
> at the skulls of *Gallimimus* at the Russian Dinosaur Exhibit
> and see if they can discern the condition from the casts there.

Holtz (pers. comm. 2000) informed me the element was misidentified in
Gallimimus.

>   A crash course in pneumatized vertebrae is not in my head to
> do right now, but only two taxa have such extensive
> pneumatization: the node defining ? == { Erlikosaurus +
> Oviraptor } and birds in the strict sense. All other taxa lack a
> fully pneumatic sacrum, *Caudipteryx* lacks pneumatization of
> the caudals and most of the dorsals, dromaeosaurids lack
> pneumatized caudals and dorsals, and ornithomimids have just a
> few more pneumatic dorsals. Tyrannosaurids appear to resemble
> dromaeosaurids more in the extensivity of pneumatopores in their
> vertebrae.

Dromaeosaurids lack pneumatized dorsals?!  I know you don't think
Achillobator is dromaeosaurid (with its pneumatized caudals(?) and dorsals),
but plenty of dromaeosaurids have dorsal pleurocoels.  Deinonychus,
Variraptor and Saurornitholestes have pneumatic dorsals, as do the related
deinonychosaurs Bambiraptor and Unenlagia.  Ornithomimids have no
pneumatized dorsals.

>   Who thinks *Avimimus* is mononykine? Mickey Mortimer puts it
> around Pygostylia, Kurzanov as a bird _sensu lato_, other
> authors around oviraptorosaurs.

Keep with the times (and rapidly changing phylogenetic trees) man. :-)
Avimimus used to be a Yandangornis+Pygostylia sister group for a while until
it settled back down as an alvarezsaurid sister group.  Still not mononykine
though, as it lacks too many alvarezsaurid synapomorphies.

>   But ignoring the morphological condition of the elements.
> There are few other groups it resembles besides oviraptorosaurs
> and dromaeosaurids, which at least suggests the jaw fragment is
> maniraptoran.

I personally think Avimimus or therizinosauroid when I see the ilium, but
haven't done any studies yet.

Mickey Mortimer