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

Again, Norman considered S. angustirostris and S.
osborni to be virtually indistinguishable.

This only (!) works as an argument if you assume a certain fixed speed of morphological evolution _and_ disregard stabilizing selection. In other words, your argument is built upon two speculations.

Apples and oranges. Turnover among large dinosaurs
was faster.

How do you know?

Saurolophus is unknown from the Campanian
or late Maastrichtian.

In North America, yes... at least so far...

I think armchair geologists

Was Shuvalov an armchair geologist? Or Sukhanov, Martinson, Russell, or Jerzykiewicz? They all expressed views on the age of the Nemegt simlar to mine, based on all the evidence.

There is so little evidence, in any direction, that the armchair is not a meaningful distinction in this case.