Re: Mononykus and Avimimus

[Dinogeorge@aol.com]

In a message dated 96-05-28 16:16:41 EDT, Thomas_R_HOLTZ@umail.umd.edu
(th81) writes:

>>Who came up with the notion that _Avimimus_ is a chimera - I hadn't
>>heard of that before.
>
>Pers. commun. from Mark Norell, and through him from the Mongolian theropod
>worker Perle Altangarel.

Ah yes--when things don't seem to be working out, invoke the old
"chimera" argument! It's been applied to _Protoavis_, and now to
_Avimimus_. >>Sigh!<<

The pelvis of _Avimimus_ is radically different from that of
_Mononykus_ in terms of the orientation of the pubis. No complete
pubis is illustrated for _Mononykus_, however; its opisthopubic nature
seems to be a hypothesis based on a small fragment of the pubis that
suggests that the shaft was oriented parallel to the ischium. Why is
this hypothesis not being tested first, before invoking a chimeric
_Avimimus_? Is there more complete pelvic material that confirms the
way it is restored in the published illustrations?

The more I deeply I read and reread the descriptions of _Mononykus_,
the less convincing they seem that _Mononykus_ had all those putative
avian features.