Re: "But What About The..." arguments (now rather short!)

["David Marjanovic" <david.marjanovic@gmx.at>]

----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Wednesday, June 05, 2002 3:43 AM

Looks like I misinterpreted what "null hypothesis" means, we left that off
in math in school. :-]

> > Your hypothesis might be restated as:  nothing but the bolide caused the
KT
> > extinctions.  If any factor other than the bolide produced a substantial
> > portion of the extinctions, then your hypothesis would be falsified.

Yes.

> Things the bolide "null" hypothesis has yet to refute: Neornithine birds
> outcompeted enantiornithine birds;

First I'd like to have some evidence that they did, and a hypothesis about
how they possibly did it.

> marsupial extinctions were due to
> competition/predation from eutherian invaders;

Metatheria and Eutheria coexisted from their divergence early in the K to
the K-T throughout Asiamerica; after it Eutheria diversified, while
Metatheria hardly did -- but it held on far into the Miocene throughout
Laurasia. Metatheria lost much of its diversity at the K-T, so probably did
Eutheria, but its fossil record is even worse.

> pterosaurs were barely
> hanging on (i.e., diversity was lowest ever _before_ K/T);

Given the few presently known fossils, I'll believe that their diversity in
the Maastrichtian was the lowest ever; but I'm not sure I'd call the 3
biggest flying animals ever "barely hanging on". I also don't know how old
things like *Ornithostoma* are.

> marine
> extinctions happened at a different time from terrestrial
> extinctions;

That has been refuted long ago by pollen correlation and by
magnetostratigraphy (I forgot that one last time). The K-T event happened
within a normal subchron of chron 29R both in the seas and in the Hell Creek
Fm -- and that subchron lasted just 50,000 years*!

* Don't know how this has been dated, but apart from sedimentation rates
Milankovic cycles, frequently recognizable in marine sediments, come to mind
as a probable possibility. (Milankovic [accent on the c] cycles have been
used to show that the P-Tr mass extinction in Austria didn't take longer
than 8,000 years, and to show that sedimentation rates dropped amazingly in
a chalk in Denmark at the K-T boundary, stayed low for several millennia,
and recovered rather fast then, but not nearly as fast as they had dropped.)

> some non-avian dinosaurs lived past the K/T and should have
> had to re-establish populations.

I do think most surviving non-neornithean dinos would have re-established
populations that would subsequently have diversified. That the latter didn't
happen is IMHO good evidence that the rest didn't happen either. I'll look
up the paper on the supposedly Paleocene dinos of India, which is the only
case I don't know a refutation for.

> I'm sure there are others.

I'm not urging you. But if you can find some, please tell me sometime.