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Re: Dinosaur Extinction (Again)



On Mon, 18 Nov 1996, Lee J. McLean wrote:

> 1) What we define as an "entire group" is largely a matter of semantics; a
> species is an "entire group" of individuals, and plenty of them were wiped
> out at the end of the Cretaceous. And birds _are_ part of the dinosaurs as
> a group. Restricting your arguments to "non-avian dinosaurs" is _pure_
> semantics.

This is the "non-extinction" theory of dinosaur extinction.  How about
this: all of the ornithischia became extinct; and all of the saurischia
(except the birds--which were probably numerous) became extinct.  If so,
what killed these groups?  This, I am sorry, is a fair question.  And
lack of suitable words to describe it does not make the problem go away.
If all of the animals I describes became extinct, why?

>
> 2) You _can not_ restrict your arguments to terrestrial forms for the sake
> of convenience. The fact of the matter is that several "entire groups" of
> aquatic life became extinct at the same time. This is highly suggestive of
> an extinction mechanism that affected both terrestrial _and_ aquatic forms.

My initial challenge was for someone to match extinction hypotheses with
the known terrestrial data.  I'm not even claiming it can be done.  But
what I am saying is that so far describing the weather at the time, or
the sea level, or even the cosmic visitors doesn't begin to explain it.
By the way, Archibald tries to do it.  I think he's unsuccessful.  But
are you saying he should not even try?  Anyway, even if these things did
happen at the same time, you still need ultimate causes: ammonites died
out but vertebrates survived relatively well.  Why?  The answer to this
lies elsewhere than in climatic data.  And so does the answer to that
other question: why did _____ become extinct?

> The first animals to go in any extinction
> event are those at the top of the food chain, and that's exactly what the
> dinosurs, and the other taxa that became extinct in their various biomes
> [is this the right term?], were.

First of all, you're violating your own 'entire group' stipulation here.
Secondly, many dinosaurs were well below the "top of the food chain".
Thirdly, extinctions occur in producers and consummers alike.

> The above scenario takes into account _all_ that is known about the K-T
> extinction event (well at least all that I know is known) and, I believe,
> explains everything.

...!

> There may be some points I am missing, however. If so,
> please put them to me or, preferably, to the list.

OK.  What killed the dinosaurs?