Re: Large last gasp of pterosaurs

[Jeff Hecht <jeff@jeffhecht.com>]

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