Re: Everything you know about the Iren Dabasu age is (right)

[David Marjanovic <david.marjanovic@gmx.at>]

>  The Iren Dabasu therizinosaur fauna still appears to
> have much more in common with that of the
> Bayanshirenian of Outer Mongolia than it does with the
> Nemegtian.  Iren Dabasu types appear very similar to
> Bayanshiree forms; both were medium sized, common and
> diverse, whereas Therizinosaurus was big and rare.

How many known segnosaur specimens are there from all three formations 
together? 5? Certainly less than 10, no? How do you intend to make 
statistically meaningful statements based on that kind of sample size...?

In addition, you're trying to do biostratigraphy with _the evolutionary 
"level" of_ big, rare terrestrial vertebrates. This is highly prone to 
fallacies.

>  Not necessarily. Recall J. Wagner's remark that
> palynomorphs have a nasty habit of showing up at
> different times in different places. I suspect that is
> true with regard to the Tsagayan and Hell Creek, and
> the apparent synchrony is illusory.

Palynomorphs still have big advantages: they occur in exorbitant numbers, 
making statistics applicable; and they are spread by wind, which means they 
have the potential to correlate terrestrial and marine sediments (which is 
usually almost as good as getting an absolute age for the terrestrial ones).

> I note btw that
> Mesolanistes, indicative of a Maastrichtian age, is
> not AFAIK, known from the Tsagayan.

It's indicative of a Maastrichtian age _and a certain environment_. Look at 
the snail species around you. Is there any that occurs in rainy forests and 
in semideserts alike?