Re: Avimimus in the Process of Revising Hou et al.

["Mickey Mortimer" <Mickey_Mortimer111@msn.com>]

Jaime Headden wrote-

> lots of interpretations of Avimimus skull PIN 3907/1, basically concluding
the actual specimen is not very similar to Kurzanov's 1981 illustration and
that it is more posteriorly placed than Kurzanov suggests.<

You may be right.  Honestly, the figure in Kurzanov 1987 confuses me, with
indistinct sutures and ambiguous structures.  I couldn't comment further
without more study.

>   In comparison to the referred cranium PIN 3907/3 (Kurzanov, 1983), the
> holotype differs in the presence of a dome further caudal to the orbit, a
> dome present on the parietal only, and in overall size is longer by almost
> 200% (the holotype braincase, comprising mostly of the parietal, is longer
> than the entire preserved cranium of 3907/3, and is 150% wider than the
> same region divided in the refered skull). Lack of fusion between the
> frontal and parietal, as well as between both parietals, indicates that
> this element cannot be an ontogenetic variant of PIN 3907/3, and that
> *Avimimus* and PIN 3907/3 are two different animals. The skull of
> *Avimimus* was a good deal larger than 3907/3, and in comparison to its
> postcrania, *Avimimus* was a very large-headed animal, similar in
> proportion to *Velociraptor*, and may have been rather raptorial or
> ornithomimid-like in appearance with a largish snout. Conversely, only the
> skull can be considered for PIN 3907/3, and this animal may have been more
> oviraptorosaurian in appearance, as well as in phylogenetic affinity.
> Previous use of the skull of PIN 3907/3 along with its cervical and dorsal
> vertebrae is therefore in error. Reconstructions using this material are
> not truly *Avimimus*.

While the possibility PIN 3907/1 and 3907/3 are different taxa seems
reasonable, the referral of the name Avimimus to the PIN 3907/1 skull seems
questionable.  Watabe et al.'s new specimen shows that characters in PIN
3907/1's postcrania (ulnar keel; carpometacarpus; hyperarctometatarsus; axis
of pedal unguals II and IV angled to sides) are present with those in
3907/3's skull (very narrow premaxilla with large narial fossa).  This shows
3907/3's skull is correctly associated with the holotype postcrania of
Avimimus.  It would probably be better to keep the name Avimimus for all the
specimens except the 3907/1's partial skull.

Mickey Mortimer