Re: Hell Creek (long)

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

----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Friday, May 31, 2002 4:32 PM

> On Fri, 31 May 2002, David Marjanovic wrote:
>
> > I will be completely shocked if we do. Because then we get a huge
> problem to explain where the Lazarus ammonites, big foraminifera,
> zalambdalestids, even stagodontids and mosasaurs are -- and why they died
> out then. :-)
>
> The fossil record is filled with "huge problems".

I mean really "huge" :-)

> It is by discovering "problems" that we progress.
> When we think we know all the answers we may
> even _avoid_ searching for evidence for alternate hypotheses.

Then "we"'d be bad scientists in the first place. Of course "we"'ll test
again and again and look with great interest at the results from every new
site. Look at that recent paper in Science on the fern spike in NZ -- it
isn't news that there's a K-T fern spike in several sites in NZ. The details
are new, though, AFAIK, and they are good evidence for a catastrophe.

> And we could
> bundle in irrelevant species: for example, zalambdalestids are survived by
> a host of similar eutherians, right?

Depends entirely on what "similar" is. And what the eutherian family tree
looks like in that region. :-)

> If so, why would one ven bother
> looking for Lazarus z...?

One thing is certain -- zalambdalestids are pretty distinct from every known
Cenozoic mammal. They'd be pretty easily recognizable. For example, they
retained epipubes, something no known Cenozoic eutherian has.

> I think you've done this before--excuse
> repeats--where on Earth one would look for early Cenozoic mosasaurs,
> ammonites, pterosaurs, enantiornithines, [...] plesiosaurs?

Everywhere, basically. :-) Marine sites aren't rare, and AFAIK even Danian
ones aren't.

> >"And why they died out then?"
> This is always a huge problem.  Fear of addressing it shouldn't limit
> research.

That I ask means that I haven't found an answer so far -- that I have tried
to address it. Really, what could do it? Competition? Certainly not. Nest
predation? Mosasaurs and plesiosaurs were viviparous.
        Ammonites passed through the P-Tr and Tr-J mass extinctions with
something like 2 species each IIRC. Means, due to their planktonic larvae*,
the few survivors spread and diversified immediately, means, we'd still have
ammonites _everywhere in the seas_ if not every last one had died at the
K-T. Wouldn't we? Same, but even more extremely, for the big K foraminifera
(don't know if they belong to a clade or anything...).
        Who's limiting research (except the new Austrian university law
threatening to come sometime soon... I digress)?

* Why is it thought they had planktonic larvae, actually? I mean, it fits
various pictures very well, but what is the real evidence?

> The very worst
> thing about the bolide hypothesis is the complacency it fosters in
> otherwise curious minds.

Does it? What I can see (may not be statistically significant) is that it
boosts curiosity in how exactly an impact could cause the observed patterns
of extinctions, isotope ratios...