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RE: Nanotyrannus

> From: Michael Lovejoy [mailto:michael@palaeoproductions.fsnet.co.uk]
> A quick trawl through the archives shows some view Nanotyrannus as a juve
> rex, and some don't. Has this been satisfactorily sorted out yet?

Satisfactorily to whom??  Therein lies the problem...

Most workers agree upon the following:
1) The type of Nanotyrannus is a juvenile, based on bone texture (among
other attributes).  The supposed evidence for adulthood are either not
actually present (i.e., supposed fusion of braincase sutures) or are
non-ontogenetically controlled features.

2) The type of Nanotyrannus shares numerous derived attributes with
Tyrannosaurus rex which are not found in other tyrannosaurids.

3) Those differences between Nanotyrannus and Tyrannosaurus are, by and
large, the same differences found between juvenile and adult Gorgosaurus
libratus or Tarbosaurus bataar skulls.

So, there are a couple of possibilities:
A) Nanotyrannus is a valid taxon, presently not known from adult specimens.
It is the sister taxon to Tyrannosaurus rex, presently not known from
juvenile specimens of the same skull length as Nanotyrannus.

B) Nanotyrannus is a juvenile T. rex.

Both are likely possibilites.

> Also, are any baby/egg specimens known for rex? I haven't heard
> of any, but
> there's a surprising number of models of rex babies available, so I'm
> wondering if I've missed something.

No eggs or babies, yet.  The "Jordan theropod" (aka Aublysodon molnari aka
Stygivenator molnari) is very likely a T. rex even younger than
Nanotyrannus, but is very incomplete.

Some day, though...

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796