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Re: Age of the Djadok(ht)a, Barun Goyot and Nemegt Formations




--- "Jaime A. Headden" <qilongia@yahoo.com> wrote:

> Tim Donovan (uwrk2@yahoo.com) wrote:
> 
> <Age estimates are again, based on more than that.>
> 
>   Yes, based on so much more data that is being
> presented. Yet for some reason
> we are discussing a *Mesolimnetes* index age, or
> absence thereof, to cite an
> age for a formation? 


  Mesolanistes. Shuvalov et al mentioned a variety of
evidence.
 
> 
> <WTF ??? Do you think the Kaiparowits and De-na-zin
> are of Maastrichtian age?
> ALL known North American parasaurolophines are of
> Campanian age. Williamson has
> repeatedly pointed out that Parasaurolophus does NOT
> occur in the Naashoibito.>
> 
>   I do admit a singular confusion of using
> Maastrichtian rather than Campanian.
> The post is still worthy despite this error.
> 
> <In fact, the apparent restriction of North American
> parasaurolophines to the
> Campanian, coupled with biogeographic links between
> Asia and America, is one
> reason I doubt Godefroit's age estimate for the
> Tsagayan.>
> 
>   I would like to point out that for over a hundred
> years, triconodonts were
> not known from the Cretaceous. Will it take a
> hundred years to stop shoehorning
> formations based on narrow interpretations of
> time-ranges?
> 
> <Buffetaut considered Tsintaosaurus a
> parasaurolophine, and it occurs in
> Djadokhta equivalent beds (Campanian).>
> 
>   So it's amazing I was pointing at it as an
> ancestral (i.e., derived EARLIER)
> taxon? This means even MORE relict lineages for
> "parasaurolophines" which may,
> or may not, be monophyletic or be a single taxon, or
> that the NA
> *Parasaurolophus* could be multiple genera. Using
> the handy-dandy
> genericometer.
> 
> At the end of his post, Tim Donovan wrote:
> 
> <Btw isn't it about time somebody corrected the
> temporal order of the Asian
> units in the title of this thread as well as the
> spelling? :)>
> 
>   I would like to point out that there is not ONE
> single consistent spelling
> for Mongolian place names,


 Yes but "Djadoktha" was never used AFAIK.

> and while formation
> nomenclature is more strict in
> spelling, I tend to be more or less plastic because
> I don't have the original
> references, at least in regards to
> Djadokhta/Djadochta. Note that during
> Mongolian geologic and palaeontologic
> investigations, Mongolia was controlled
> by China, Russia, and then on it's own, with a shift
> towards various spelling
> systems as placenames were translated from Mandarin,
> Pinyin, Russian,
> Mongolian, and English interpretations. So give this
> bit a little latittude.
>
> 
> <No, see above, they apparently existed in the
> Djadokhtan period, which I
> suspect was also the age of the Tsagayan.>
> 
>   There is no such thing as a "Djadokhtan period". I
> have noticed that Donovan
> (and I've said this before which has been ignored)
> that he will mix up land
> mammal age names, land vertebrate age names, and
> formation and group geological
> names with geological stages and periods. 


 As I pointed out repeatedly, radiometric dating of a
Djadokhtan locality indicates a late Campanian age.
Recent work suggests the Baynshirenian ended by the
Campanian.



>The
> Cretaceous Period, for example,
> is a WHOLE lot larger than the Djadokhta (Djadochtah
> or Djadochta) Formation.
> So if we want to quibble about consistency of useage
> or spelling, let's get
> right particular.
> 
>  using genera to predicate an age assaignment
> (e.g., *Saurolophus*) but it
> is only to use related genera (*Tyrannosaurus* and
> *Tarbosaurus*) to do the
> same, while similar to identical taxa throughout the
> Mongolian, NorthAmerican
> Campano-Maastrichtian are not being use to collapse
> the ages for these
> respective formations? 

  Basically I'm just repeating the conclusions of
Shuvalov, Martinson, Osmolska, Russell, Jerzykiewicz
etc, concening the early-mid Maastrichtian age
estimate for the Nemegt. And this is NOT based on just
taxa. The Nemegt couldn't be as old as Campanian
because far underlying beds are late Campanian. Again
see Shuvalov.


>This being my main problem
> with using alpha taxonomy as
> biostrat markers. Convenient, but as a scapegoat,
> and it narrows thinking.
> Also, I am curious why Donovan has not replied to
> Mickey Mortimer?

  I replied by mentioning the discovery of
Bactrosaurus from Bayshin Tsav; it is also known from
Iren Dabasu.
  
> <Godefroit suggested a NA origin.>
> 
>   And if the data backs up any interpretation, then
> we'll see. But this will
> require ALL of the data, not some of it; and in this
> case, all of the data
> should be equal, not some "better" than others. So
> far, that data is leading me
> away from thinking that taxonomy and thus index taxa
> have any reality regarding
> biogeography. There do not seem to be any absolute
> boundaries in regards to
> taxonomic distribution, even among island taxa
> today, except regarding mass
> extinctions and other environmental factors
> 
> "Innocent, unbiased observation is a myth." --- P.B.
> Medawar (1969)
> 
> 
>               
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