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RE: Maastrichtian extinction and synonymous sauropods

Tim Donovan wrote:

> > no less than four chasmosaurine species existing at the very
> > end of the Cretaceous: _Triceratops horridus_, _T. prorsus_, 
> >_Diceratops hatcheri_ and _Torosaurus latus_.
>  True, but IIRC she indicated that only one-horridus-was common. 

Common in the fossil record, that is.  Remember, you cannot judge the
abundance of species in a past habitat based on their relative abundance in
the fossil record.  There are preservational and ecological factors to
consider.  To put it simply, animals that hung around lakes and rivers were
more likely to end up at the bottom of said lakes and rivers, and therefore
more likely to be fossilized.

>Do you have a better explanation for the mid Maastrichtian extinctions 
> and turnover?

As I understand, your explanation is that _Tyrannosaurus took over the
world.  I think if you want your hypothesis to be taken seriously, you have
to, at the very least, demonstrate what novel characters _Tyrannosaurus_
possessed that made it (in your words) an 'archpredator'.  What did
_RTyrannosaurus_ have that its predecessors (_Albertosaurus_ etc) didn't -
and which rendered lambeosaurs and centrosaurs utterly helpless, thereby
driving these taxa to extinction.

Tim W.