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Re: Large last gasp of pterosaurs



At 9:59 PM -0500 1/21/04, John Bois wrote:
On Wed, 21 Jan 2004, Nick Pharris wrote:

The hostile environment is inferred
from the presence of a
bolide and a knowledge of the laws of physics. Pterosaurs became extinct at
the same time, so it is reasonable to hypothesize that the hostile environment
(inferred on independent grounds) had something to do with it. No circularity
here.

But pterosaurs as a clade seem to have had a long, gradual extinction. This implies some other cause than a single event. If these (probably biological) causes are sufficient to explain the majority of pterosaur extinctions, I would say you need some direct evidence to look for some more exotic cause. [clipped]

What you're postulating is the compromise scenario I've seen suggested for the dinosaurs elsewhere -- the pterosaurs were vulnerable because they were in a long, slow decline and the K-T impact finished them off. The conventional view of the extinction of the trilobites at the Permo-Triassic boundary is just that -- they had been in a long decline, and the P-Tr finished the last of them. If that's true, what "killed the pterosaurs" becomes a matter of definition, although I'd say it tends to be splitting hairs. -- Jeff Hecht