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RE: 100 MA North America
> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]
> On Behalf Of firstname.lastname@example.org
> Sent: Monday, October 10, 2011 5:19 PM
> To: email@example.com
> Subject: 100 MA North America
> Does the basal tyrannosaurs Appalachiasaurus and Dryptosaurus
> from Appalachia [eastern North America] trace its roots
> directly back to the Late Jurassic Stokesosaurus, middle
> Cretaceous Cedar Mountain tyrannosauroid, the european
> Eotyrannus, or Asian tyrannosaurs?
Not enough is published yet on the Cedar Mountain form to tell. However, most
recent phylogenetic analyses place Appa. and Drypto.
as closer to Tyrannosauridae proper than to the Asian Xiongguanlong (and
Raptorrex, if that is indeed a distinct taxon), and much
closer to these than to Stokesosaurus, Eotyrannus, Dilong, or the
Nevertheless, things become somewhat muddled on this point. The position of
Asian Alectrosaurus is not certain: it is in the same
grade, certainly. It appears that Bistahieversor is closer to Tyrannosauridae
than are the Appalachian forms.
So at present it looks like the ancestor of the entire clade "Appalachian forms
[grade] (?+Alectrosaurus) + (Bistahieversor +
Tyrannosauridae)" may be Asian, but that most of the radiation within it was
within North America, with subbranches (Tarbosaurus,
Alioramus, Zhuchengtyrannus) returning to Asia during this interval.
(Note, however, "returning to Asia" is a bit of a muddled concept anyway:
during at least some of this time Laramidia and
eastern/central Asia are one connected landmass).
Thomas R. Holtz, Jr.
Email: firstname.lastname@example.org Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Faculty Director, Science & Global Change Program, College Park Scholars
Mailing Address: Thomas R. Holtz, Jr.
Department of Geology
Building 237, Room 1117
University of Maryland
College Park, MD 20742 USA