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Re: Extinction

On Fri. 21 April, Peter Sheehan wrote:

> The problem is that William's statement about the decline has no evidence 
> to back it up.   Personally, I have seen no evidence presented that there 
> was a 
> gradual decline of dinosaurs at any scale in the Hell Creek.  In fact, 
> the only field study of the Hell Creek designed to test the hypothesis 
> rejected a gradual decline. 

        A quick search of my database turned up TWO papers on this subject
directly relating to the Hell Creek.  One suggests a gradual extinction,
and the other a "catastrophic" extinction.  (I suppose any extinction
would be "catastrophic" if you happen to be in the species involved.) :-)

J. Smit & S. Van der Kaars, 1984, Terminal Cretaceous extinctions in the
Hell creek area, Montana: Compatible with catastrophic extinctions,
Science 223:1177

R.E. Sloan, J.K. Rigby Jr., L.M. Van Valen, D. Gabriel, 1986, Gradual 
dinosaur extinction and simultaneous ungulate radiation in the Hell Creek 
Formation, Science 232:629-633

There are also comments on the Sloan et al. paper in Science 234, pp 
1172-3 by L.J. Bryant et al.

        I haven't read any of these papers, but I thought I'd throw a 
little fuel on the fire.