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Re: Tyrannosaur Evolution and Bagarataan



--- David Marjanovic <david.marjanovic@gmx.at> wrote:

> >  AFAIK, saurolophines are unknown from the
> apparently
> > Djadokhtan equivalent beds at Laiyang.
> 
> How many dinosaurs in total have been found there so
> far? Does that number 
> give us a reason to think that we'd already have
> discovered saurolophines if 
> any were present?


 A fair number of specimens are known from at least
three levels, indicating the presence of lambeosaurs,
including Tsintaosaurus if a parasaurolophine, Tanius,
ankylosaurs, sauropods and theropods. You could have
pointed out that at least two Udurchukan localities,
and unit 2 of the Horseshoe Canyon, are dominated by
one hadrosaur genus, yet much different types are
known from geographically close localities of about
the same age. At least one saurolophine,
Kerberosaurus, did IMO exist in the preNemegtian
period in Asia, albeit not at Laiyang AFAIK.

> 
> > It is likely IMO that the sauroloph niche was
> already
> > occupied in Asia by Keberosaurus to almost mid
> > Maastrichtian, and the Tsagayan types were then
> > supplanted by American immigrants.
> 
> What do you suggest that that niche was? 

 I don't know kind of vegetation saurolophs
ate-presumably something fairly low which was present
in inland areas. It is noteworthy that any kind of
hadrosaur could probably exist in the Amur area yet
there is no evidence of Saurolophus or any other
Maastrichtian American type in thae supposedly late
Maastrichtian Tsagayan despite the accessibility of
remoter parts of Asia by c late early Maastrichtian. 
> 
> 




                
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