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Re: Hell Creek (long)



In a message dated 5/31/02 11:42:53 AM Eastern Daylight Time, jbois@umd5.umd.edu writes:


<< As people a wont to do re dino disappearance from Hell Creek: isn't this
just a local extinction.  I mean, there are probably plenty of places
sharks visit that mosasaurs don't. >>

      Certainly. Abyssmal depths and certain freshwater habitats come to mind as possibilities. But the big sharks like Cretolamna and Squalocorax shared the same waters as mosasaurs and disappeared also.

<< And, just to make sure I understand--before the K/T there were what, sharks, mosasaurs, teleosts,.,echinoderms...and after the K/T--in this location--sharks only?  Or do you mean that there are plenty of other things _but among large verts_ sharks
only? >>

      I don't know about "plenty", but I know of no other large vertebrates there besides sharks. In North Dakota's Cannonball Sea sharks predominate (teeth). But they are not the same sharks like Squalocorax and Cretolamna that feature so largely in late K waters. John Hoganson has described the vertebrates of the Cannonball, I'd have to look it up to see if he's found any teleosts. I'm not qualified in the invert department, life's too short.
                   Maybe the mammal guys have a better way of doing this in their biostratigraphy. Instead of getting all wrapped up in extinction they speak in terms of latest appearances, I believe . DV