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Re: Dinosaur Extinction (Again)
John Bois wrote:
>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_
>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?
It _is_ a fair question, but your initial post stated that the dinosaurs
were the only "entire group" to become extinct at the K-T. But as calling
the non-avian dinosaurs an "entire group" _is_ pure semantics, then it is
both a false and utterly irrelevant statement.
>> 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.
I did not make the stipulation. I was merely dismissing your argument about
your perception that the dinosaurs' was a unique extinction event at this
time. All the evidence suggests that it was related to the many other
extinctions that were going on at the same time - a fact which you ignore.
Also, just because the animals at the top of the food chain will be the
first to go, that does not mean they will be the _only_ ones to go.
Extinctions will cascade down the food until there is either no life left,
or the extinction event passes. At the K-T, the event stuck around long
enough to take out all the non-avian dinosaurs, but didn't go down far
enough to make it to the placental mammals. Ironically, I think the reason
that the marsupials were harder hit than the placentals was because, at the
time, they were more successful. So the placentals survived by being so
_unsuccessful_ at climbing the food chain.
>> 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?
If you'd actually _read_ the body of my post, you would see that I have
already explained this in detail. Try reading it again without trying so
desperately to hang on to an untenable idea.
P.S. How is the mouse that you were only going to feed eggs going? Did you
give up or is it dead?