Re: Tyrant Notes

[Dinogeorge <Dinogeorge@aol.com>]

In a message dated 98-04-07 00:57:42 EDT, th81@umail.umd.edu writes:

<< The name "Dinotyrannus" has so far only been used by George Olshevsky.
Greg
 Paul coined "Albertosaurus megagracilis" for a specimen he now considers a
 subadult T. rex.  (I agree with Greg on this point).  Ralph Molnar
 considered this a distinct species in his original report and in his later
 review of the Tyrannosaurus skull anatomy: I don't know what his current
 thinking is. >>

Ralph is the only person to have extensively examined _Tyrannosaurus rex_
material (for his doctoral dissertation) and the _Dinotyrannus megagracilis_
material. At the time he published his description, he didn't think the _D.
megagracilis_ type material belonged to _T. rex_, on the basis of numerous
minor anatomical differences--and thought it might even be an adult
_Nanotyrannus_ (then _Gorgosaurus_) _lancensis_. I don't know what he thinks
about the material today, and if he's now willing to sink _D. megagracilis_ as
a junior synonym of _T. rex_, then I will certainly follow his judgment. But
when last I corresponded with him on this (a few years ago--about the time I
wrote the Gakken article on tyrannosaurids), he still considered _D.
megagracilis_ distinct from _T. rex_, and allowed Tracy access to some of his
unpublished figures of the material so he could prepare the illustrations for
the Gakken article. Tracy's pix therein are the best yet published of the
available _D. megagracilis_ material.

We really have little idea what a subadult or juvenile _T. rex_ might look
like; there is still much debate, for example, about whether _Nanotyrannus
lancensis_ is a juvenile _T. rex_, even though it has a very nice skull
available for study. We also cannot be certain that there was only one Lance-
age tyrannosaurid, so that, for example, we can't be sure that all the
specimens that have been referred to _T. rex_ really do belong to that
species. They've been assigned to it not on the basis of diagnostic _T. rex_
characters but simply because they're large, tyrannosaurid, and from the
Lance/Hell Creek. (Except for the Lance/Hell Creek bit, these are also the
reasons that _Jenghizkhan bataar_ keeps being referred to the genus
_Tyrannosaurus_, even though it has a much slenderer muzzle, a narrower
occiput and more laterally pointing orbits, a higher dentary tooth count, and
numerous other cranial differences.) I'll go along with any thorough study of
the known _T. rex_ material (I think the Larsons are working on this), but I
would like to see with my own eyes those characters that make a particular
specimen a _T. rex_, starting with the holotype specimen at Carnegie.

In point of fact, tyrannosaurids are very difficult to study, because the type
specimens are often mounted for display and are inaccessible, because they're
gigantic, and because many specimens have been doctored up with plaster in
funny ways, often acquiring features that they didn't have when they died
70-odd million years ago. One of these days someone in quest of a Ph.D. will
actually get the job done. That's when the genera _Jenghizkhan_ and
_Dinotyrannus_ will at last be properly reevaluated, instead of being casually
dismissed with comments like, "Aagh, they're just more _Tyrannosaurus_." (Are
they _Tyrannosaurus_? Show me.)

Somebody want to give me the grant money, I'll be happy to chase
tyrannosaurids all over the world myself.

By the way, if it could ever be shown that there really was only one large
Lance tyrannosaurid, then its name would have to be _Manospondylus gigas_
(unless of course someone petitions the ICZN to suppress that name).