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Late Maa North American tyrants (was RE: Validity of Alioramus)
> From: Demetrios M Vital <email@example.com>
> Is Nanotyrannus lancensis late Maastrichtian like Tyrannosaurus
> I was
> under the impression that all tyrannosaur fossils from the
> Maastrichtian of
> North America are assigned to T. rex. Is this true?
Kind of. _Albertosaurus sarcophagus_ is a distinct form from the early
Maastrichtian of North America, but some people have referred any
tyrannosaurid fossil from the late Maastricthian of North America to _T.
Actually, there are two styles for these referrals:
I) Uncritical: "Hey, I found a tyrannosaurid from the late Maastrichtian of
western North America!" "Then it must be _T. rex_."
II) Critical: "Hey, we've examined the late Maastrichtian tyrannosaurid
fossils from western North America, and found them to be consistent with
being different growth stages and variations of a single species,
Other tyrannosaurid taxon names for late Maastrichtian western North
American dinosaurs include _Stygivenator molnari_ (originally _Aublyosodon
molnari_), _Dinotyrannus megagracilis_ (originally _Albertosaurus
megagracilis_), and _Nanotyrannus lancensis_ (originally _Gorgosaurus
lancensis_). However, many workers now consider most or all of these
species to be different growth stages of a single species, _Tyrannosaurus
rex_. This does not preclude, however, the discovery and/or demonstration
of a second tyrannosaurid species from the late Maastrichtian of western
Hope this helps.
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