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RE: New review paper of tyrannosaur paleobiology in Science, with new phylogeny

I'll second Denver's observation here.  Analyzing a known young specimen (based 
on histology) as an adult is simply improper and bound to result in incorrect 
phylogenetic placements.  The fact Carr's own analysis incorrectly places 
juvenile Tyrannosaurus (in the same position Alioramus emerges in) should all 
the proof one needs.  I still believe Alioramus is probably a juvenile 
Tarbosaurus (and that A. altai is certainly a junior synonym of A. remotus).  
As I said on my site, the 
  fact most differences could be explained by ontogeny, coupled with the unique 
  similarities present in Alioramus and the contemporaneous Tarbosaurus 
  strongly suggest the former is a juvenile of the latter. The alternative 
  by Brusatte et al., where a distinct genus known only from juvenile specimens 
  and based on characters largely found in juvenile tyrannosaurs is 
  with a taxon it is not the sister group of yet shares autapomorphies with, is 
  considered unlikely.


Mickey Mortimer

> Date: Thu, 16 Sep 2010 18:35:38 +0000
> From: df9465@yahoo.co.uk
> To: dinosaur@usc.edu
> Subject: Re: New review paper of tyrannosaur paleobiology in Science, with 
> new phylogeny
> Can somebody explain to me the weird trend in Brusatte tyrannosaur articles
> where he ignores some of his own points about ontogeny.
> On the one hand, he states that tyrannosaurid skulls elongate through 
> ontogeny,
> teeth become more robust, yet on the other hand claims these same characters 
> are
> important features of Alioramus, which the authors acknowledge is based on a
> juvenile specimen and derives form the same deposits as Tarbosaurus. IIRC
> Alioramus is justified by the apparent elaborate skull ornamentation. However,
> skull ornamentation in dinosaurs can often be less pronounced/elaborate in
> adults (Horner & Goodwin, Triceratops). Brusatte cites this in the Alioramus
> description, but makes the opposite claim.
> ----------------------------------
> Denver Fowler
> df9465@yahoo.co.uk
> http://www.denverfowler.com
> -----------------------------------
> ----- Original Message ----
> From: "Thomas R. Holtz, Jr." 
> To: DML 
> Sent: Thu, 16 September, 2010 12:18:55
> Subject: New review paper of tyrannosaur paleobiology in Science, with new
> phylogeny
> http://www.sciencemag.org/cgi/content/full/329/5998/1481
> Brusatte, S.L., M.A. Norell, T.D. Carr, G.M. Erickson, J.R. Hutchinson, A.M.
> Balanoff, G.S. Bever, J.N. Choiniere, P.J. Makovicky, & X. Xu. 2010. Review:
> Tyrannosaur Paleobiology: New Research on Ancient Exemplar Organisms.
> Science 329: 1481-1485.
> Tyrannosaurs, the group of dinosaurian carnivores that includes
> Tyrannosaurus rex and its closest relatives, are icons of prehistory. They
> are also the most intensively studied extinct dinosaurs, and thanks to large
> sample sizes and an influx of new discoveries, have become ancient exemplar
> organisms used to study many themes in vertebrate paleontology. A phylogeny
> that includes recently described species shows that tyrannosaurs originated
> by the Middle Jurassic but remained mostly small and ecologically marginal
> until the latest Cretaceous. Anatomical, biomechanical, and histological
> studies of T. rex and other derived tyrannosaurs show t
> rapidly, were capable of crushing bite forces,
> had accelerated growth rates and keen senses, and underwent pronounced
> changes during ontogeny. The biology and evolutionary history of
> tyrannosaurs provide a foundation for comparison with other dinosaurs and
> living organisms.
> -----
> A review paper, not new research as such. But Brusatte & Carr have pooled
> their resources to produce a new phylogeny:
> Tyrannosauroidea
> |--Proceratosauridae
> | |--Kileskus
> | `--+--Proceratosaurus
> | `--+--Guanlong
> | `--Sinotyrannus
> `--+--Dilong
> `--+--+--Eotyrannus
> | `--Stokesosaurus
> `--+--Xiongguanlong
> `--+--Dryptosaurus
> `--+--Raptorex
> `--+--Appalachiosaurus
> `--+--Bistahieversor
> `--Tyrannosauridae
> |--Albertosaurinae
> | |--Albertosaurus
> | `--Gorgosaurus
> `--Tyrannosaurinae
> |--Alioramus
> `--+--Utah taxon
> `--+--Daspletosaurus
> `--+--Tarbosaurus
> `--Tyrannosaurus
> Congrats, folks!
> 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
> http://www.geol.umd.edu/~tholtz/
> Fax: 301-314-9661
> Faculty Director, Science & Global Change Program, College Park Scholars
> http://www.geol.umd.edu/sgc
> 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