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Tyrannosauridae (Alioramus, etc.)
Sounds good to me, and I assume the general consensus is that
Siamotyrannus probably isn't tyrannosauroid, and Amblysodon is a nomen
dubium. Therefore I come up with:
TYRANNOSAURIDAE sensu lato (= Tyrannosauroidea)
8 Tyrannosaurus (incl. Nanotyrannus)
Gorgosaurus may be sister group only to Albertosaurus, in which case it
would be recoded 4B.
From: "Thomas R. Holtz, Jr." <email@example.com>
To: <firstname.lastname@example.org>, <email@example.com>
Subject: RE: Validity of Alioramus
Date: Fri, 22 Jun 2001 10:24:57 -0400
As for _Alioramus_: there actually ARE a few potential synapomorphies of
this taxon with _Tarbosaurus_ and/or _Tyrannosaurus_. However, it
falls further down my tree than these guys plus _Daspletosaurus_ plus
_Gorgo._ + _Alb._. Wouldn't be too surprised, however, it it might not
creep further up with more information.
That being said, I think that the extremely well-developed nasal crests,
among other features, preclude _Alioramus_ from being a juvenile of
> From: firstname.lastname@example.org [mailto:email@example.com]On Behalf Of
> Speaking of problematic tyrannosaurids, what is the current view of
> Nanotyrannus? I have examined the actual specimen, and it sure
> doesn't look
> like just a juvenile T. rex to me! However, I am far from being
> able to give
> a qualified opinion...thus I ask how others feel about it being a
> valid taxon?
Thom Carr's 1999 paper in JVP has pretty well established the juvenile
status of this individual. Additional, as he mentions, there are some
derived features in this skull otherwise only found in _T. rex_. So, we
could validly argue a couple of positions:
*_Nanotyrannus_ is a valid taxon, closely related to _T. rex_, known
present only from a juvenile skull
*"Nanotyrannus" is a specimen of juvenile _T. rex_.
At the Armour Symposium, Currie argued for the former, and Brochu & I for
the latter, although none of us with particular fervor. There are a couple
of hypothetical specimens which would help establish the validity of
_Nanotyrannus_ as its own taxon:
*An adult specimen of tyrannosaurid which was distinct from _T. rex_
which clearly showed derived features shared with the _Nanotyrannus_ type
*A juvenile specimen of tyrannosaurid of the same length as the
skull which was distinct from _Nanotyrannus_ and which also showed clear
rex_ synapomorphies not found in the _Nano._ skull.
Note that the "Tinker" specimen is MUCH too large to help clear up the
latter situation: the teeth of "Tinker", for example, have roots so long
that if you tried to place them in the _Nano._ maxilla they would blast out
through the top of the skull!
Barring the discovery of either of the hypothetical specimens discussed
above, I'm willing to take the route of accepting "Nanotyrannus" as a
juvenile _T. rex_.
Thomas R. Holtz, Jr.
Department of Geology Director, Earth, Life & Time Program
University of Maryland College Park Scholars
College Park, MD 20742
Phone: 301-405-4084 Email: firstname.lastname@example.org
Fax (Geol): 301-314-9661 Fax (CPS-ELT): 301-405-0796
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