re: "rare" bones in the Hell Creek

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>...Only a few thousand (dinosaur bones) have ever been found in the Hell
Creek..."


I can't speak with ghreat authority about the "rarity" that represents,
but the entire eastern Late Cretaceous outcrop has yielded roughly an
order of magnitude fewer dinosaur bones.  Yet, we seem to see distributional
patterns (chronological and geographic) in occurrence based on these: for
example, nodosaurs are unknown east of western Alabama; _Dryptosaurus_
sensu stricti is unknown pre-Maastrichtian, etc.

The point is that a paltry few thousand specimens over a wide area are
sufficient to define a pattern.  _If_ thjat pattern shows disappearance
 a meter below the Iridium boundary, it lends credence to the reality
of the dissappeearance (I wish I could erase prior text on this
primitive system) as a biological phenomenon rather than as a Signor-Lipps
effect result.

david schwimmer
schwimm@uscn.cc.uga.edu