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Re: How Did Hadrosaurs Survive?




From: jonathan.r.wagner@mail.utexas.edu
To: rob@dinodomain.com, msdonovan66@hotmail.com, dinosaur@usc.edu
Subject: Re: How Did Hadrosaurs Survive? Date: Wed, 30 Oct 2002 07:52:52 -0600 (CST)


Rob Gay wrote:
>Isn't Charonosaurus Maastrichtian?

Yes, but probably not Late Maastrichtian. To be fair, it has been claimed to
be "Lancian," based on palynological work. However, it does not appear to fly.
As I recall, the "Lancian age" for the deposits is based on the presence of
Wodehousia spinata, a palynomorph that lends its name to the North American
pollen zone that corresponds to Lancian strata in the northern Great Plains of
North America. However, the palynologist who worked with Bolotsky on the Amur
region deposits had earlier established that this palynomorph is present at a
much earlier time in Russia than it is in North America

Thanks for a timely repitition of what you posted onlist a year ago.


(I can't recall, for
that matter, if the North American FAD W. spinata is in the W. spinata Zone or
before it). So the "evidence" of "Lancian" lambeosaurines is thus far wanting.


With the exception of that Hell Creek lambeosaur recently reported. But it was found stratigraphically low, and certainly seems rare, so maybe lambeosaurs were essentially gone by the Lancian.

I'm sure someone will eventually come up with uncontrevertable evidence of
these buggers eventually.

>   The Wangshi and later Tsagayan environments had diverse hadrosaurs but
>wre supplanted by a Nemegtian fauna with essentially just Saurolophus.

I would caution you strongly to avoid the assumption that the Wangshi
is "Campanian" and therefore not correlative with the Nemegt. The Wangshi fauna
appears to be reasonably consistent with interpretation as a "lowland"
correlate of the Nemegt fauna. North American "Campanian upland" faunas are
arguably more similar to "Edmontonian" faunas than to contemporaneous lowland
faunas, at least hadrosaur-wise. It is certainly plausible that a similar
situation might hold for the "Edmontonian" of Asia. Do you know of a recent
paper that actually provides some objective measure of the age of the Wangshi
fauna?

It has been known for years that Buffetaut identified an ankylosaur specimen from the Wangshi as Pinacosaurus, which argues for a Barungoyotian age i.e. early Barungoyotian, inasmuch as Pinacosaurus was apparently supplanted by Saichania and Tarchia in the Barungoyotian beds which directly underlie the Nemegt. Lambeosaurs ranged well inland in Mongolia since the time of Bactrosaurus, and probably continued to do so in the Barungoyotian period, given tracks at Abdrant Nuru and elsewhere. If the Wangshi and Tsagayan were of Nemegtian age, why didn't their primitive lambeosaurs range into Omnigov etc? They must have been supplanted by a Nemegtian community composed largely of American immigrants such as Saurolophus c mid Maastrichtian.



It certainly could have happened in the three years since I've been
allowed to read primary literature.

Wagner


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