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Re: Ocean EcoSystems Unexpectedly Stable (fwd)



----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Wednesday, May 22, 2002 5:31 AM

> > > ammonites had suffered a Cretaceous-long decline.
>
> > A decline throughout the K? Which strange sort of competition or
whatever
> > could cause that? I mean, the K was longer than the time that has passed
> > since!

And how could evolution simply stop to act on them?

> > In some places ammonites do appear to die out gradually, but in
> > others in the vicinity they last to the very end.

Maybe I can find that old ref that compared 2 places in France and Spain...
in one place the ammonites appear to die out gradually, in the other the
same species stay to the bitter end.

> http://www.mpt.org/learningworks/teachers/ntti/8-12/extinctwks4.html
>
> This link copies the figure from Officer and Page's The Great Dinosaur
> Extinction Controversy.

Has got pretty bad reviews... very similar to Feduccia's books.

> Data is from Wiedmann 1969 (ref. if needed) and is
> unchallenged as far as I know.

Of course not. (Have _any_ data stayed unchallenged for this long time!?!)
Just recently a pdf was mentioned onlist that reported the last ammonite of
the Western Interior Seaway _within the last 10 centimeters_ below the K-T
boundary in quite a thick layer. So fig. 1 is wrong in showing all ammonites
as dead meters before the boundary. -- BTW, here is a world-famous ammonite
worker (unfortunately responsible for all paleontology of the museum...)
that you can probably ask (he appears to be rather short of time): Dr.
Herbert Summesberger, www.nhm-wien.ac.at/NHM/Geolog/Staff/Summ/HPSumm.htm.
Haven't asked him myself yet, but so far he has agreed with the impact
scenario in every guided tour. :-)
        Have one more look at fig. 2. The curve that the "species ranges"
form is _so_ neat that it looks like a _textbook illustration_ of the
Signor-Lipps effect! :-)

> If the record represents reality ammonites
> were more successful early in K.

This alone wouldn't mean a gradual extinction was present. BTW, can I assume
that the data for fig. 1 are from the Western Interior Seaway? In this place
it's easy to invoke the regression that must have gradually driven all
deep-water and stenohaline species out of that place (but not the whole
world).

Fig. 2 is funny. Compare the dots and the graph :-D

> Also, in same link, notice inoceramid clam extinction earlier than K/T.

Maybe too few species to be statistically significant. Maybe the local
effects of regression, see above. The species to the right stays as long as
the last ammonites, so it may not have died out before the boundary... of
course, I know even less about inoceramids than about ammonites :-)

> Saw a paper in recent (Lethiae sp?)

Lethaia?

> journal talking about predation as cause for
> their extinction.

Predation? Is that serious??? ~:-| -- Lethaia is available in the
geosciences library here. I'll look for that paper. (It wasn't the April
issue, was it? :-> )

> > the extinction of elasmosaurids at the K/T boundary
> > thus appears to be sudden rather than gradual."
>
> Is this now the accepted view?

Looks like it.

> Seems just yesterday that they were extinct
> before the boundary.

Well, apparently like me most people on this list don't regularly read the
literature on the marine K. Many refs in the paper I cited are by no means
from "yesterday".