Re: phylogenetic position of Achillobator, Yandangornis, etc.

[Nick Longrich <nrlongri@midway.uchicago.edu>]

        I keep getting avimimus coming out smack-dab in the middle of the
oviraptors, near oviraptoridae and  caenagnathids. This is based on:
        beak
        edentulous premax
        edentulous dentary
        crenellate beak
        fusion of premax
        dentary medially curved to symphysis to form U-shaped symphysis
        fusion of cranial bones
        fusion of premaxillae
        rodlike jugal bar
        downcurved, pendant paroccipital processes
        pterygoids closely appressed and fused to base of skull (!!!)
        elongate retroarticular
        ?long, shallow sliding articular joint for the quadrate

Jaime was saying something about the bug-eyed look to the skull of
oviraptorids, that seems to describe avimimids pretty well. Admittedly some
of the above are also found in birds.

        and in the postcrania:

        anterior regions of iliac blades inclined medially
        digit IV subequal to II
        propubic pelvis
        wide pelvic canal
        short pubic boot elongate anterior, short posterior



        Many of the supposedly birdlike features, such as
        -tarsometatarsus
        -large hypapophyses
        -antitrochanter on the ilium

        Are actually found in the dromaeosaurs, troodontids, and
oviraptorids. Kurzanov's flight-feather attachment point is pretty
questionable (and kinda moot considering they are in Caudipteryx), and
there is a carpometacarpus in the type of Oviraptor philoceratops so it's
kinda questionable what it means to find one in Avimimus...  Avimimus also
lacks some of birdlike features seen in paravians, such as the way that the
posterior iliac blade comes to a little point, or any sort of
hyperextension in the toes. Not to diss Kurzanov, in retrospect he looks a
little overzealous but remarkably prescient in his ideas on Avimimus.
        Anyways, I think most of theropod phylogeny is up in the air but
I'd lay down serious money on this thing being oviraptor if the parts are
associated, and maybe a couple oviraptor relatives if they aren't from the
same animal (I think I heard something about some of the vertebrae being
troodontid though). I just have a measly ~250 character matrix, but I coded
pretty much every single 1, 0 and ? from illos in the literature when I
couldn't from fossil; I tried running the head and postcrania separately
and got both as oviraptor relatives. My cynical side wonders what this
proves; I am always disappointed when I don't get what I want out of PAUP,
and suspicious when I get back what I thought I should.
I think you likely got Protarchaeopteryx dead-on, tho, though we
desperately need better fossils of that animal to prove this. Those
super-long caudal transverse processes, e.g. are classic oviraptorosaur.

-N