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Re: Age of Gobi formations



>   Wodehousia spinata argues for an early Maastrichtian age for the
Tsagayan.

Ignorant question: Is that palynomorph so specific? There was a time when
people thought that ostracods, charophytes and I'm too lazy to look up what
else were capable of dating Guimarota as middle Kimmeridgian. The fossils
have turned out to have longer ranges, and now Guimarota is regarded as just
Kimmeridgian.

> It is hard to believe the Nemegt fauna, with Horseshoe Canyon aspect
hadrosaurs, is older i.e. was supplanted by, a Campanian aspect fauna with
far more diverse hadrosaurs-exactly the reverse of what occurred in NA.

All that business about "aspects" sounds so intuitive and unscientific to
me... sort of like "evolution level"... I don't know anywhere near enough of
the paleoenvironments and the paleoecology of hadrosaurs to tell if it
should perhaps be expected that the faunas of western NA and central Asia
changed in opposite ways. I assume there are people onlist who know the
paleoenvironments well enough. I don't think anyone knows enough about
hadrosaur ecology.
        Just for the record, I have no opinion on the subject of this
thread. :-]

> And Asia and NA had biogeographic connections around then.

Nobody knows how intermittently or continuously, and it isn't clear how much
of a filter the Bering landbridge, which was very far north, was.

>  All things considered, including size, isn't Tarbosaurus still most
similar to Tyrannosaurus,

According to most analyses... yes.

> and isn't it at least more likely to be closer temporally than
Daspletosaurus?

By this logic, you are more likely to be closer temporally to *Proconsul*
than to *Macaca*. It's unfair of me to interpret things like the following
into your mind, but was that part of the confusion about "evolutionary
levels"...?

>   Altan Ula IV has yielded the same Nemegtian dinosaurs as other
localities. Maybe the Barun Goyot interfingers there too.

Sounds like Mongolia is still underexplored geologically.