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Re: Tyrannosaur Evolution



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

> ----- Original Message -----
> From: "Tim Donovan" <uwrk2@yahoo.com>
> Sent: Monday, February 14, 2005 12:31 PM
> >
> >  The east lacked big ceratopsids etc.
> 
> While this is probable (tyrannosaurids and
> ceratopsids seem to have evolved 
> in Asiamerica and would have needed to cross a
> sea...), are you sure you 
> aren't confusing absence of evidence and evidence of
> absence here?


 AFAIK, the Navesink and other eastern NA units
represent lowland environments with hadrosaurids;
nodosaurs are also known in the east. These are the
taxa and environments associated with an abundance of
Triceratops etc in the west. The absence of
ceratopsids in the kind of environments which seem
right for them in the east certainly suggests they
weren't there.
> 
> > Note that Saurolophus, an American immigrant,
> > seems well adapted to the predator.
> 
> How do you mean? 

   It certainly seems to have been the most abundant
herbivore alongside T. bataar, based on skeletal and
trackway evidence.

> 
> 



                
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