Re: late night thoughts: adults only

[don ohmes <d_ohmes@yahoo.com>]

You are right in a sense, although I don't feel there is any functional 
difference between Asian and American tyrannosaurs/sauropods. I accept that by 
using the term "T. rex", I inadvertently restricted aspects of my comments to 
N. America. Still, I had thought that the overlap between T. rex and sauropods 
in N. America was minimal and early, not zero. Not that my assessment of the 
physical vulnerability of sauropods is affected, or my perception of the 
stealth-through-immobility options/capabilities of T.rex and functional 
equivalents (notably including allosaurids).

Nor was I aware that the difference in last appearance times of sauropods in 
Asia/North America was so dramatic and clearcut. It seems likely 
preservation/collection bias scenarios can be eliminated as explanations. If 
that is correct, is there a 'mainstream' explanation?

Don

----- Original Message ----
From: David Marjanovic <david.marjanovic@gmx.at>
To: DML <dinosaur@usc.edu>
Sent: Friday, June 8, 2007 7:32:56 AM
Subject: Re: late night thoughts: adults only

> I understand that consensus is that when T. rex proper was in full flower 
> sauropods were getting kind of scarce... might have been one prey/predator 
> race where the predator won. Maybe Horner is right in that they were down 
> and out at the end; but only if they had run out of the good stuff, in my 
> opinion.    }:D.

You misunderstand.

- North America seems to have lost all of its sauropods at the end of the 
Cenomanian (though the bad fossil record between the Cenomanian and the 
Campanian may be fooling us). That's _thirty million years_ before the first 
*Tyrannosaurus*. In the Campanian, "*Alamosaurus*" turns up (though it 
apparently stays in the southern part of the continent), and _then_ we get 
*Tyrannosaurus*.

- Asia seems to have had sauropods all the way to the end of the Cretaceous; 
the appearance of *Tyrannosaurus* does not seem to have made a difference.