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Re: Theories on the extinction of dinosaurs



-----Original Message-----
From: Seosamh <seosamh@chesapeake.net>
To: Dinosaur Mailing List <dinosaur@usc.edu>
Date: Friday, November 12, 1999 8:14 AM
Subject: Re: Theories on the extinction of dinosaurs



(in speaking of impact, vulcanism, and atmosphere)



>Given that these three phenomena are accepted as real, based on
>the available fossil evidence, what "smoking gun" do people still
>seek? A plausible explanation of the synergistic effects of these
>events? Solid evidence that reptiles, birds, mammals, et al.,
>had/have some type of "immunity" to these effects?
>
>I'm trying to assemble some meaningful description of the interactions
>among these observed (in the fossil record) events.


The impact occurred...the indicating iridium layer is the  "smoking gun".

Volcanoes do not produce  free oxygen.

Atmosphere...may certainly have been affected, but to what extent?And how?
Seems to me that birds would be the first to go if the atmospheric gases
became toxic. They were used by miners to detect poisonous gases long before
the miners would collapse.

So why were birds, mammals and reptiles immune?

How about this for a scenario:

1)large bolide strikes, and kicks up enough dust particles to block out
photosynthesis for a few months.
2) all herbivores die off for lack of food.
3)all large warm-blooded carnivores die off
4) insects survive
5)insectivores (ie. small birds, small mammals, cold-blooded lizards)
survive
6) some large cold-blooded predators that can survive a few months without a
meal
7)plants grow again from seed
8)existing biosphere radiates genetically to fill unused niches, new
herbivores develope, mammals get their chance, because the secondarily
flightless birds are now toothless, and their wings have become too
specialized to become very usefull as "mammal graspers",...theropods loose
their "reign of terror"...(at least on the scale of the Mesozoic...despite
the presence of a few "terror birds" of the Paleocene).

I believe a similar scenario of "blocked photosynthesis" has been
proposed...and accepted for the marine enviornment at the end of the
Cretaceous. As for those large marine reptiles??? Maybe they were warm-
blooded? (it seems a possible corollary to this hypothesis, as if they were
cold-blooded, surely some of them might have survived with the sharks...no?)