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Re: Tyrannosaur Evolution
On Saturday, February 12, 2005, at 08:49 AM, Mickey Mortimer wrote:
Many possible theories, including the newly introduced tyrannosaurids
chasing down and killing their competition, or scaring them to the
point of petrification from their own meals. If it wasn't for Homo
sapiens industrialization redndering so much of North America
undiggable, we'd have a much better idea.
Joe Cantrell wrote-
Why did tyrannosaurs become so large and advanced in western North
America while the east harbored a > frozen relic of the
pre-Baynshirenian-Dryptosaurus- down to the late Maastrichtian?
Keep in mind our record of Eastern North American Late
Campanian-Maastrichtian tyrannosauroids basically consists of one
specimen (Dryptosaurus holotype), six teeth, a partial maxilla and
I believe there's an 8-inch claw as well, presumed to belong on the
hand. Imagine if it turned out to be a foot claw. .
I don't know how big any of the fragmentary specimens is, do you?
"The Encyclopedia of Dinosaurs" estimate is 18 feet for the known
specimen. Also, it is mentioned that the specimen was found in marine
deposits in New Jersey, suggesting that the poor guy drifted out to sea
before becoming fossilized.
So I don't think we have a good idea of the variation that existed
there and then. Western North America had its own smaller basal
tyrannosauroid too (Labocania), and the Nemegt had Bagaraatan.
I imagine the Western Interior Seaway[and the nasty critters in it] had
a good deal to do seperating the Eastern & Western faunas.