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Re: Age of the Barun Goyot, Djadoktha and Nemegt Formations
Jaime Headden wrote:
But maybe I can counter Donovan's statement above by saying that someone
thinks that the two *Saurolophus* species are different genera? Researcher
researcher, who will win!? (While I'd bank on Norman for his credentials, I
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.
Tim (not Donovan).