Aublysodontines (was RE: Horner on NBC Nightly News (T. rex hunting evidence))

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> T. Mike Keesey
>
> On a similar topic, can anyone sum up why all the "aublysodontines" are
> now considered juvenile tyrannosaurins? Does anyone still debate this?
> Someone's been asking me and I can't give a solid answer.
>

See DinoGeorge's "Tyrannosaurian Implosion" articles on the archives for
some of the justification:
http://www.cmnh.org/fun/dinosaur-archive/2001Jan/msg00670.html
http://www.cmnh.org/fun/dinosaur-archive/2001Jan/msg00671.html

It's a case by case basis:
_Stygivenator/Aublysodon molnari_: Skull features once used to distinguish
it from other tyrannosaurs have proven to be post-mortem distortion (e.g.,
the "step" in the dentary) or are known to be part of an ontogenetic series
of changes in other tyrannosaurs (e.g., the shape of the frontals), and thus
are unrealiable for distinguishing what is a new taxon and what is just a
young 'un.

The Kirtland Shale "aublysodontine" was already known to have some features
(including the convex tablike process on the postorbital) otherwise only
known in _Daspletosaurus_.  Carr &  Williamson (in the Dinos of New Mexico
volume) argue on this and other evidence that the specimen is referrable to
_Daspletosaurus_.

_Shanshanosaurus_ was never known to possess definite derived features with
any of the "aublysodontine" (including the as-yet-undescribed premaxillary
teeth).

_Alectrosaurus_ DOES seem to be distinct (especially the referred specimens,
although these are not yet described nor are the definitely referrable to
_A. olseni_), and seems to lie outside the classic tyrannosaurines.

Hope this helps,

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796