RE: The position of tyrannosaurs (was Re: Armour Symposium Recollections)

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

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Dinogeorge@aol.com
>
> In a message dated 5/14/01 3:26:54 PM EST, tholtz@geol.umd.edu writes:
>
> << Please note that Olshevsky's "tyrannosauroid implosion" represents
>  Dinogeorge's accepting taxonomic decisions many of the rest of us agreed
>  upon since the late 1990s, via Thom Carr's work and others. >>
>
> Well, most of you people still think Albertosaurus is three genera rather
> than just one with three species (not a terribly big deal, but
> part of the
> implosion nonetheless). And for some reason many of you still
> want to include
> Tarbosaurus within Tyrannosaurus, even though there is a lot more
> morphodistance between Tarbo and Tyranno than there is among the three
> Alberto "genera."

These are matters of generic synonymy rather than phylogenetic affinity:
i.e., taste rather than position.  There still doesn't exist a
"genericometer" or some other test to demonstrate when two species should be
grouped in the same genus rather than split.  However, I and Currie and
Brochu (at least) all use _Tarbosaurus_ now, and Chris and Thom Carr use
_Albertosaurus_.

In reality, we've all converged (in terms of phylogenetic position, if not
generic taxonomy) on Greg Paul's 1980s version, anyway...

> And why was Aublysodontidae/Shanshanosauridae
> still showing
> as a separate group in the year 2001 at the Tom Holtz
> tyrannosaurid website
> (part of Tree of Life)?

That is based on work to be published shortly, but written in 1999.  Thom
Carr & Tom Williamson's work since put paid to the Kirtland Shale
"aublysodontine" (to be fair, though, I do point out the shared similarity
in the orbital region...).

> The more interesting paradigm shift for me presently is removing the
> pterosaurs from Archosauria and reclassifying them as derived
> prolacertiforms.

and

>I think Dave Peters has nailed this one.

I agree with that wholeheartedly!!

                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