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Re: Albertosaurus



At 11:40 AM 1/31/97 -0500, you wrote:
>In a message dated 97-01-31 07:34:57 EST,
>T.Williams@cclru.randwick.unsw.edu.au (Tim Williams) writes:
>
><< _Tarbosaurus bataar_ - Ken Carpenter regards this as a species of 
> _Tyrannosaurus_.  George Olshevsky, however, discerns two separate 
> genera and species - _Tarbosaurus efremovi_ for a smaller version, 
> and _Jenghizkhan bataar_ for the larger one. >>
>
>Figuring out whether _Tarbosaurus_ is distinct from _Tyrannosaurus_ using
>morphology is very difficult because of the restoration work done on the
>_Tarbosaurus_ specimens before they were mounted for display. The Russians
>restored missing parts on their specimens by modeling them after American
>tyrannosaurids, which may account for some of their apparent phyletic
>closeness.
>
Actually, there are more problems than just that.  As Dinogeorge has pointed
out elsewhere, many tyrannosaurid skulls have been (unfortunately) restored
after better known skulls, and not just in North America.  (The AMNH
Albertosaurus sarcophagus skull (not on display) has a fair amount of
overly-T. rex features in plaster, for example).  However, inspection in
person can help sort some of this out, as can flash photography.

More than that, there is left-right variation in the specimens.  The frontal
notch is quite apparent on the left side of the type of T. bataar, whereas
the left side looks as if it has a nice supraorbital torus.  Other examples
of left-right variation exists on other skulls (the famous AMNH 5027, for
example).

Having seen the diversity and variation within the Tyrannosaurus rex skulls
(very apparent if you go to BHI, where so many [originals and casts] are
available in one place), I would not be surprised at all if a morphometric
analysis would place the type of T. bataar within the "cloud" of T. rex.  Of
course, one would have to actually do such an analysis in order to say "yea"
or "nay".

Nevertheless, given the characters which are available in bone (not
restored), the big Asian forms DO fall out extremely close to T. rex.


Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"To trace that life in its manifold changes through past ages to the present
is a ... difficult task, but one from which modern science does not shrink.
In this wide field, every earnest effort will meet with some degree of
success; every year will add new and important facts; and every generation
will bring to light some law, in accordance with which ancient life has been
changed into life as we see it around us to-day."
        --O.C. Marsh, Vice Presidential Address, AAAS, August 30, 1877