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Re: K/T extinction (forams and birds)
I don't know enough about forams to know how many species or genera
survived K/T. But I can say that a minimum of about 60-70 genera survived,
because about 60-70 families of forams survived. I would guess probably at
least a hundred genera and perhaps several hundred species of forams
survived. Of course, many of those may have been devastated to the point of
near extinction. By comparison, the number of foram families that went
extinct in the Cretaceous was probably only 6-10, and even some of those may
have gone extinct before K-T. In any case, forams as a group did a lot
better than any vertebrate group that I know of.
Forams are small and have large populations, so you can kill off
99.999% of the individuals and still have large sustainable populations of
many species (I would guess benthic species did better than planctonic
species). In my opinion, foram diversity would have suffered far less than
the higher organisms that heavily depended on them for food. Don't know
much about ammonites and what they ate, but perhaps this was a factor in
their extinct(?). Bacterial diversity was probably affected little if at
all at generic and higher levels.
There was probably some aspect of freakish luck in some cases of what
survived---Gondawana land vertebrates certainly had the edge over those in
North America (what a great time to be in Antarctica or Australia. But this
becomes less important as you go to sea (especially the deeper sea) and the
farther down food chains you were. Tiny decomposers like bacteria are the
most immune to bollide disasters except for particular species dependent on
a particular host that went extinct.
----Been a long day & time for bed, Ken
From: "David Marjamovic" <David.Marjanovic@gmx.at>
To: "The Dinosaur Mailing List" <firstname.lastname@example.org>
Subject: Re: K/T extinction (forams and birds)
Date: Tue, 15 May 2001 22:33:43 +0200
> Forams were not wiped out. Class Foraminiferea actually came
> K/T almost unscathed in terms of ordinal diversity. Order Involuntinida
> (which made it through the Permian extinction) apparently did not make
> through K/T (but who knows, it may be found in the early Paleozoic
> But most Cretaceous foram orders made it through and are still
> today: Monothalamida, Allogromiida, Astrorhizida, Haplophragmiida,
> Spirillinida, Miliolida, Lagenida, Robertinida, Globigerinida,
> Cassidulinida, Nonionida, Plaorbulinia, Asterigerinida, Discorbida, and
> Rotaliida. Sadly, Order Orbitoidida made it through K/T, but only
> to the Eocene.
How many species of these orders survived? 1? 2? 100?
Still not a single crown-group placental has turned up from the LK AFAIK,
which might mean that only one species survived (casts additional doubt on
NA marsupials being outcompeted by invading placentals). From biogeographic
and phylogenetic considerations, 3 species at minimum must probably have
survived (the ancestors of Xenarthra, Afrotheria and "Boreoeutheria" [ =
rest]). (If we don't accept the molecular clock estimates, that is; I
don't.) However, this is surely a minimum because even in NA alone more
species of marsupials and multituberculates survived.
> (disaster doesn't seem like strong enough
> word for K/T--- a ghastly time to have been alive, especially on land).
It was even worse, IMHO. More tomorrow.
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