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Early Maa _Gorgo._?



Phillip Bigelow wrote:
> Moral of the story:  If it's a "big ripper of a tooth", and it's latest
> late Maastrichtian in age, it probably fell off of a _T. rex_.
> _Albertosaurus_ and _Gorgosaurus_ may have still been around in the
> early Maastrichtian, but after that, the time of their ultimate demise
> gets a little foggy.

Hurm.

_Albertosaurus_ at present is known ONLY from the early Maastrichtian.

I am unaware of any diagnostic _Gorgosaurus_ material from the early
Maastricthian.

Note that, postcranially, it is very difficult at present to distinguish
these two forms.  Specimens of mid-sized tyrannosaurids should not be called
"_Albertosaurus_" or "_Gorgosaurus_" if they lack skull material.  Just
label them as tyrannosaurine and be done with it.  (Note also that this
means that just about every non-Judith River, non-Horseshoe Canyon Campanian
and early Maastrichtian tyrannosaurine is not diagnostic to one or the other
at present.  Change those faunal lists, guys!).

(This isn't that much different for ceratopsid or hadrosaurine or
lambeosaurine specimens: if you don't have the head, it is difficult to
determine which genus you have).

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661