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Re: STEVE - the newest T. rex



In a message dated 95-08-20 22:50:38 EDT, pjanke@maroon.tc.umn.edu (Paul R
Janke) writes:

>STEVE is the sixth T. rex to be found in Harding county SD,
>and the 22nd major T. rex fossil discovered since 1900.
>       9 in S. Dakota
>       8 in Montana
>       1 in N Dakota
>       1 in Wyoming
>       3 in Canada

Why does everyone think that every large Lance tyrannosaurid is automatically
_Tyrannosaurus rex_? Nobody has shown that all these specimens exhibit a set
of features that could be used to define the species; indeed, nobody has even
set down in print any characters uniquely defining the species and
distinguishing it from other tyrannosaurids (by going back to the type _T.
rex_ specimen and redescribing it, for example). For this reason, despite the
wealth of material, the genus _Tyrannosaurus_ strictly speaking remains a
_nomen dubium_(!).

I recently received from Japan a copy of the guidebook to "The _T. rex_ World
Exposition." There is a section toward the beginning of the book with a
gallery of photos of most of the world's supply of _Tyrannosaurus_ skulls.
Although they all look somewhat alike--as might be expected from
tyrannosaurines--there are also many differences that could be of taxonomic
significance, unless they happened to be put there in plaster by the
preparators. It would be nice to see just how much of each skull is real
bone, how much is cast, etc., but this information does not exist in print.
If everyone thinks only one species is present, then plasterers feel
justified in restoring missing parts to look like those of other specimens,
and soon the idea of a single species becomes a self-fulfilling prophecy. It
makes life easier--but is it the truth?

The type skull at the Carnegie Museum is hopelessly distorted and needs
extensive remodeling just to resemble a tyrannosaurid skull, but its picture
appears in dino books all too often with no disclaimers of any kind. I've
reread Osborn's original papers on it and the type material of _Dynamosaurus
imperiosus_, and I agree with prevailing opinion that the two species are
synonymous, even though the relevant comparison has not been published.
So--I'm not a hopeless splitter. But AMNH 5027 is curiously different from
the Carnegie type in cranial and postcranial anatomy, and I'm not yet
convinced that these differences can be accounted for by ontogeny, sexual
dimorphism, and so forth.

Regarding the gracile morph: the pelvis figured by Peter Larson in
"Tyrannosaurus sex" is taken from an illustration of AMNH 5027 by Osborn and
is known to be "all too gracile": the sacral vertebrae are laterally crushed
almost into two dimensions (their pneumatic nature succumbed to the forces of
geology, so to speak). The degree of crushing is unknown, so until someone
illustrates a new "gracile" specimen, we should perhaps take the idea of
robust and gracile morphs with a tiny grain of salt. (I'm not saying it's
wrong, I'm saying it's by no means as well established as everyone seems to
think.)

G.O.