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Re: Tyrant stuff (no longer ranting) (was RE: Rant (was RE: Details on SVP 20...



In a message dated 11/9/02 6:04:23 AM EST, qilongia@yahoo.com writes:

<< For dinosaurs, at least, *Elmisaurus* (based on
 morphological similarity, including several autapomorphies withing all of
 Dinosauria), *Prenocephale* (on former *Stegoceras* crania, based on
 morphological similarity), *Tyrannosaurus*/*Tarbosaurus* (same),
 *Saurolophus* (and same) have all apparently crossed the bridge from one
 side, to the other. *Albertosaurus*, some hadrosaur fragments, and some
 ceratopsians have been found in northern Alaska at the critical Campanian
 point where is it possible the Barun Goyot/Nemegt formations may have been
 deposited with the similar Judith River Group. It is not unlikely to
 suggest that eastern Siberia will yield these taxa as well in what may be
 the Asiamerican Corridor. >>

Certainly there was a Bering bridge before the Santonian. That's why the same 
>families< show up on both sides of it. But there was no land connection 
during the Campanian, a land connection that may have been restored only at 
the very end of the Maastrichtian. In between those times, the regions were 
essentially isolated, and any putatively "congeneric" species that occur 
there then are very likely convergent or plesiomorphic rather than truly 
congeneric. If it was so easy to get across, why are there no ceratopine or 
centrosaurine ceratopians in Asia (for example)? Easy for one means easy for 
all.

By the way, Sullivan (pers. comm.) is reconsidering the North American 
Prenocephale species; he will be making new genera for them shortly.