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Re: JVP 25(2): New Dinos, Birds, Discoveries



> It derives from the
> Czehbánya Formation,
> Santonia,


 Santonian?

>   Sampson, S. D. and M. A. Loewen. 2005.
> *Tyrannosaurus rex* from the Upper
> Cretaceous (Maastrichtian) North Horn Formation of
> Utah: Biogeographic and
> paleoecologic implications. _JVP_ 25(2):469-472.
 

 Tyrannosaurus is known from all of the intermontane
units including the Javelina, if Brochu is right about
TMM 41436-1, but preservation is generally poor in
those units. IMO T. rex is underepresented in some of
the Alamosaurus bearing units due to taphonomy. It
should be noted that Tarbosaurus, probably closest to
the ancestry of T. rex, is abundantly preserved in the
Nemegt formation, which had a fair number of
titanosaurs. That suggests titanosaurs did influence
tyrannosaur evolution. Tyrannosaurus may have evolved
larger size to overcome titanosaurs in far inland
environments, then spread to the lowlands.

 Btw, ankylosaurids may have been present in  the
Leptoceratops habitats but they were hardly among the
dominant taxa there. AFAIK only two A. magniventris
specimens are known from the Scollard.



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