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patterns in extinction, etc.



In discussing the extinction of mosasaurs, plesiosaurs, pterosaurs, and 
crocodiles, Nick Pharris said:

> It doesn't really matter if they were *abundant*.  It is simply the
> fact that all those distantly related groups (along with other, even
> more distantly related groups) independently snuffed it at the same
> time.

I don't think we can demonstrate that those groups snuffed it at the same 
time--i.e., that's not a _fact_.  It's an _interpretation_ that their 
demise was synchronous.  Incidentally, you would be compounding this 
interpretation by asserting that this time was the same as for a number 
of marine creatures. (No--this does not contradict my earlier claim that 
we can no longer doubt that there was a large bolide impact at or near 
the end of the Cretaceous.) 

Mr. Bois (forget the first name--sorry) said:

> Levinton closes with this tantalizing, dogma-breaking idea: "It may
> also be that the end- Cretaceous extinction crisis may not have been
> one of reduced food, or even the result of an impact."

I think that most commentators on the terminal Cretaceous extinction
allow that its cause has not been certainly determined--even those who
favor the impact scenario.  There's no dogma.  But I'm still sitting
here waiting for an equally competent alternative.

Darren Naish said:

> The late Bev Halstead, for example, argued that small herbivorous
> mammals would have been numerous enough and destructive enough to
> compete effectively with large herbivorous dinosaurs.  [snip]...I
> don't agree, and obviously there are problems.  [snip]...how tough
> and open to interpretation such situations can be.

Good assessment of the situation!  Today, do population explosions of 
prairie dogs (or other "furballs") mean trouble for bovids, antelope, or 
elephants?  (This is a rhetorical question.)

Darkclaw (Cory Gross) said:

> ...if the dinosaurs did die out gradually, over the span of millions
> of years, then shouldn't we see evolution and diversification of
> mammals to fill the niches that the dinosaurs were dropping away
> from?

We might expect to see the evolution and diversification of _something_
to fill their niches.  Apparently we don't see this happening.  Thus, a 
claim of competition from something else, leading to direct ecological 
replacement of dinosaurs, cannot be supported by the evidence.

> BTW, what is it with some palaeontologists that they seem to have
> such a disdain for the work of of other scientists in other
> disciplines? The way some of them(us/whatever) talk about
> physicists, astronomers, and geophysicists almost disgusts me.

Good point, but it goes both ways.  I think it's a universal human
characteristic.  You think you're smarter than most everybody else,
and your group is better than all the others.  Even Luis Alvarez, who
knew nothing of paleontology or paleontologists, said they are just
"stamp collectors."  Gee, it disgusts me that he was so disdainful of
us!  So, you see, it's not just paleontologists.


*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu