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Re: New hadrosaur paper

>  *Amurosaurus riabinini* Bolotsky and
> Kurzanov, 1991 (Dinosauria, 
> Hadrosauridae) is described on the basis of numerous
> disarticulated bones 
> from the Maastrichtian Udurchukan Formation 

  Apparently a new name for the Tsagayan. It was also
used in reference to Kundur beds.

> Blagoveschensk, Far Eastern 
> Russia. Comparisons with North American palynozones
> and their 
> well-calibrated ages suggest that this formation is
> late Maastrichtian in 
> age.

 I wonder if Wodehousia spinata orignated in Asia in
the early Maastrichtian and spread to North America by
the late Maastrichtian, via the same Bering bridge
which enabled Saurolophus to cross into Asia. That
would create the illusion of a late Maastrichtian age
for the Udurchukan.

> It is shown that *A. riabinini* is a valid
> species, characterised by 
> cranial and postcranial autapomorphies. A
> phylogenetic analysis, based on 40 
> cranial, dental, and postcranial characters,
> indicates that this taxon 
> occupies a relatively basal position within the
> lambeosaurine subfamily as 
> the sister-taxon of a monophyletic group formed by
> the parasauroloph and 
> corythosaur clades.

  It is hard to believe east Asia was really isolated,
enabling primitive hadrosaurs to persist there in the
late Maastrichtian i.e. after Saurolophus and other
taxa spread to Asia. There is a possible nodosaur,
presumably of American origin. Apparent Tarbosaurus
remains are known from all Tsagayan or Udurchukan
localities, albeit not necessarily in the same units
which yielded Amurosaurus, Charonosaurus etc. A.
periculosus (=Tarbosaurus) is from an unnamed unit at
Jiayin, not the Tsagayan, which yielded Charonosaurus.
AFAIK, Tarbosaurus teeth from Blagoveschensk are
stratigraphically higher than the
amurosaur/kerberosaur remains. Maybe the Udurchukan
fauna was typical of Asia down to about mid
Maastrichtian-it is reminiscent of the Campanian
Laiyang fauna- but was abruptly replaced by a
Nemegtian fauna with American immigrants.

> This cladogram also demonstrates
> that lambeosaurines 
> have an Asian origin. In eastern Asia, lambeosaurine
> dinosaurs dominate late 
> Maastrichtian dinosaur localities,

 I doubt it.

> whereas this
> group is apparently no 
> longer represented in synchronous localities from
> western North America .

  So Boyd was wrong?

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