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





>  However, I think it is possible, if not likely, that some taxa can have 
>ontogenetically "juvenile" features while still being adult (paedomorphism). 
>

If it is paedomorphic then it would have ancestrally possessed a normal high 
tyrano skull, but selected later for an elongate skull. In which case 
padeomorphism makes the elongated skull a derived not primitive feature in that 
taxon.

The point is that the Alioramus altai holotype is immature. So is Jane the 
T.rex. Both have elongate skulls, but for Alioramus the elongation is 
considered 

a true character of the taxon, whereas with jane it is considered an 
ontogenetic 

feature. Which is it?

My issue is with the ontogenetic status of this and other recently named 
tyrannosaurids. How is it possible to tell a juvenile of a derived derived 
high-skull tyrannosaurid from an adult of a basal elongate-skull 
tyrannosau(o)id? And do you think that a defensible job is done in the 
description? Postcranial fusion is unreliaable: Carr and Williamson said that, 
and anyway, postcranial fusion is incomplete in Alioramus altai: the authors 
state as much and state that it is immature.




>When it comes to generally "juvenile" skeletal and proportionate features in 
>otherwise fundamentally "adult" skeletons that exhibit various other "adult," 
>proportional or ossification trends, one may be permitted the ability to 
>assume 

>or propose a slight paedomorphic trend. Note, for example, that 
>*Xiongguanlong* 

>has an enormously slender and elongate skull, large rounded orbit, and 
>extremely 
>
>elongate preorbital skull, and large skull relative to its body, but is 
>nonetheless not apparently a juvenile. There should be no constraint that a 
>juvenile morphology should suppress any and all conclusions toward a more 
>mature 
>
>status, especially given the meagre study so far produced for the taxa 
>presented.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever
left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
> 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 pre
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
>
>
>