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Raptorex: some thoughts


Unfortunately the Raptorex online publication fell on a) a day when I left
work early to FINALLY see "dinos on ice" (aka "Walking with Dinosaurs: the
Live Experience"); b) right before a day taken up by lots of meetings; and
c) right before I head out of the country. So I have to keep this brief.

A) Provenance and disposition of the specimen: Sedimentary matrix and
associated fossils with the specimen are entirely consistent with it being
from the Lujiatun Member of the Yixian Formation, which is also consistent
with the type of preservation. That said, there is indeed the possibility
that it might be from some other unit (and thus possibly some other time).
In fact, if memory serves it was being advertised as "Henry the
Alectrosaurus" for some time. Chemical and palynological study of the matrix
might be quite informative one way or the other.

The story behind its sale, the conditions for the description of the
specimen, and its being turned over back the Chinese has been dealt with in
some of the news items.

B) Anatomy: just plain cool. Except for the size, it has nearly all the
salient features of Tyrannosauroidea behind the neck, and a fair number of
cranial ones. Incidentally, barring the arm shortening being convergent
between it and Tyrannosauridae, this means that the big arms of the
Appalachiosaurus mount are almost certainly incorrect (given that Appa is
almost certainly closer to Tyrannosauridae than is Raptorex).

C) The name: a lot of people have complained about the genus name. Me, I
have problems with the trivial nomen, because I could think of a very
appropriate one. (Well, I can dream, can't I? Sniff, pout... :-)

D) Phylogeny: Hey, I'm working on it! In between this and a few other
newbies (new specimens of known taxa, and other new taxa in the pipeline)
I've been called upon and inspired to work on a revision of basal
coelurosaurs focusing on Tyrannosauroidea. Stay tuned. That said, I would
say that it is almost certainly closer to Tyrannosauridae than are Guanlong,
Dilong, Proceratosaurus, Stokesosaurus, and Eotyrannus, and almost certainly
farther away from Tyrannosauridae than is Appalachiosaurus. How it will fall
relative to Xiongguanlong and Dryptosaurus remain unsettled in terms of a
bigger analysis. But morphologically I would be very surprised if it fell
basal to Guanlong, Dilong, Proceratosaurus, Stokesosaurus, and Eotyrannus.

Take care. And--for those going to the meeting--see you in Bristol!

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661               

Faculty Director, Earth, Life & Time Program, College Park Scholars
Faculty Director, Science & Global Change Program, College Park Scholars
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA