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RE: Michael Matheny of the Tinker team speaks out on www.kidrex.com (was re: Tyrannosaurid ontogeny)

From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of Martin Barnett
Following our brief, yet inciteful discussions of the Tinker story here on the list, I posted my concerns on the website's notice-board, hoping for a response.  At 11:44 this morning it arrived.  This is what he said:


 Do Tinker's teeth rule out the Nano question? Well, consider this. While Tinker may have had different teeth as a baby, as a 60% adult sized juvenile he had the same teeth as Mom and Dad. Tinker is the same size as an adult Nano. Adult Nanos have totally different teeth than Tinker. This would certainly be a strong indicator that Nanos are NOT T.rexes.  

"Tinker is the same size as an adult Nano".  An interesting comment, given that our one and only specimen has juvenile bone texture!  Regardless of whether or not _Nanotyrannus_ is a juvenile _T. rex_ or not, the only known skull of _Nanotyrannus_ is of a juvenile.  If it is a distinct taxon, we do not know its adult size.


Also, a warning concerning so-called "adult Nano" teeth: we DO have evidence of another Lancian tyrannosaurid, distinct from the _Nanotyrannus_/_T. rex_ morphology, with _Nanotyrannus_-like blade-like teeth: _"Aublysodon" (or _Stygivenator_) molnari_.  Until someone can find a way to distinguish between isolated teeth of these two taxa, it is best not to assign such isolated maxillary or dentary teeth to one or the other taxon.


Also, I read a description of the Nano skull that mentioned that the snout was sharper, more 'foxlike' and that Nano's eyes may have been set for forward on the face giving better binocular vision than a T.rex.

From what I understand of Tinker's skull remains, they are classic T.rex in shape."(Snipped)

As Carr discusses in his recent JVP article, there are some major shape changes in skulls of growing tyrannosaurids (just as there are in other dinosaurs: no surprise there).  Until such time that a _T. rex_ juvenile the same size as (or smaller than) but distinct in form from the type of _Nanotyrannus_ is discovered, or an adult _Nanotyrannus_ distinct in form from _T. rex_, this matter will be a matter of debate.
So, sorry for those who want the answer RIGHT NOW: it simply isn't available yet.

                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): 301-314-7843