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Re: Age of the Barun Goyot, Djadoktha and Nemegt Formations



Speaking of Probactrosaurus, the exhibit of dinosaurs
from China currently on display at the Field Museum:

http://www.fieldmuseum.org/dinosaurdynasty/

Includes a skeleton of an iguanodontid which the
display material states is an unnamed genus similar to
Probactrosaurus.  Does anyone know if a description of
this specimen will be out soon?

Guy Leahy

----------------------------------------------------

--- Tim Williams <twilliams_alpha@hotmail.com> wrote:

> Jaime Headden wrote:
> 
> >   But maybe I can counter Donovan's statement
> above by saying that someone 
> >else
> >thinks that the two *Saurolophus* species are
> different genera? Researcher 
> >vs.
> >researcher, who will win!? (While I'd bank on
> Norman for his credentials, I 
> >and
> >others will note he tends to be a lumper and has
> dismissed variation in
> >geographic areas due to individual variation,
> 
> Several ornithopod species that have been "lumped"
> in the same genus are 
> currently in the process of being de-lumped (or
> should that be un-lumped?).  
> (For example, one famous ornithopod genus is about
> to be pared down in 
> dramatic fashion.)  However, although Norman
> apparently has a reputation as 
> a "lumper" (see above), he did recognize that
> _"Probactrosaurus" 
> mazongshanensis_ does not belong in the genus
> _Probactrosaurus_ (among other 
> features, the dentary tooth crowns of
> _mazonhshanensis_ more closely 
> resemble those of _Altirhinus_ than _P. gobiensis_).
> 
> Norman D.B. (2002). On Asian ornithopods
> (Dinosauria: Ornithischia). 4. 
> _Probactrosaurus_ Rozhdestvensky, 1966. Zoological
> Journal of the Linnean 
> Society 136: 113-144.
> 
> And while certain parts of the euornithopod tree may
> be "lumpy", other parts 
> may be oversplit when it comes to the number of
> genera.  Just look at 
> _Hypacrosaurus_, _Corythosaurus_ and _Lambeosaurus_,
> or _Edmontosaurus_ and 
> _Anatotitan_.  The same is pretty much true for
> advanced ceratopsids.  The 
> validity of genera often lies in the eye of the
> beholder, and so makes for a 
> poor yardstick in biostratigraphy.
> 
> Cheers
> 
> Tim (not Donovan).
> 
> 
>