Re: (extinction)

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

----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Tuesday, July 02, 2002 1:52 PM
Subject: Re: 2 x Re: small dinosaurs with feathers


> Marsupials suffered only local extinctions--

Metatheria as a whole suffered greatly. Before there was Deltatheroida,
Peradectidae, Stagodontidae and Pediomyidae (the so-called Neometatheria,
which include Sparassodonta and the crown-group Marsupialia, are thought to
be the sister group of Pediomyidae but haven't been found yet in the
Mesozoic -- *Alphadon* is not an opossum but a peradectid). Not to mention
*Asiatherium* whose phylogenetic position is apparently badly known. After
it there were only Peradectidae, Neometatheria and whatever Herpetotheriidae
is. At least one of the first two (if they are different -- apparently very
little work has been done on their phylogeny... for a long time they were
all considered opossums) survived into the Miocene in North America, Europe
and maybe Asia (Asia is underresearched, but had metatherians in the Eocene,
Oligocene, I think Paleocene, and who knows...). The deltatheres, on the
other hand, are gone. Unfortunately their LK records are so far limited to
Mongolia where still no K-T boundary section has been discovered. (EK
deltatheres from NA are known -- *Atokatherium*). Stagodontidae are known
from the Hell Creek Fm and from Mongolia. The rich (IIRC middle to late)
Paleocene sites of Inner Mongolia haven't yielded a stagodontid so far; in
NA none are known from the Puercan (the lowermost local stage of the
Paleocene), apart from remains in the Bug Creek Fm that have been reworked.
Pediomyidae is AFAIK only known from the LK of NA and possibly the Paleocene
of SA, but not the Paleocene of NA. I can't discuss whether
*Monodelphopsis*, the pediomyid from Itaboraí, is a pediomyid, because I
won't know a pediomyid if I see one, apart from the fact that I haven't seen
an illustration of any so far. :-)
        No K metatherians have yet been found outside (western?) NA and
Asia.

> and those have been
> (reasonably, in my view) attributed to placvental invasions.

Look what eutherians there are in the Hell Creek Fm... two cimolestans and a
leptictid. No member of these groups is known from the K of Asia. Eutherians
as a whole, however, were present in NA at least since the EK
(*Montanalestes*).
        And then there are the eutherian extinctions in Asia. There is that
clade (Asioryctitheria?) that includes *Asioryctes*, *Ukhaatherium*,
*Kennalestes*, Zalambdalestidae and maybe Zhelestidae. It is present in the
youngest Mongolian records of the Mesozoic and absent in all Paleocene
strata that have been searched so far.
        In a competitive scenario you'd expect only metatherians first, then
the first eutherians arrive and diversify, while the metatherians suffer a
fast but gradual extinction, then the eutherians remain alone. This is
simply not a pattern I can find in the secondary literature. I haven't found
a mention of such a shift in the Hell Creek fauna so far, and after all
Peradectidae survived (but it was hit badly, losing Alphadontinae [sounds
paraphyletic, I don't know], so that the latter has only been put into
Peradectidae in the last few years).
        I've read a few times that metatherians, apparently Peradectidae,
are thought to have immigrated to NA, where they hadn't been before, from
Asia at the Paleocene-Eocene boundary. This appears to contradict other
sources... can someone disentangle my confusion?

> Crocs live.

Not all. Baurusuchidae snuffed it, unlike the closely related Sebecidae. The
specialized turtle-eater *Brachychampsa* went with it. All that diverse
Notosuchia stuff is gone, though nobody knows if right after the late
Maastrichtian or later.
        It is expected that generalized crocs survive such an event. They
aren't dependent on "green food chains", they can eat carrion and fast for
months.
        Any comments from the croc experts? What old blunders in croc
systematics have I repeated? :-)

> Chelonians,

http://research.amnh.org/users/esg/ has found a few groups that did die out
at that time. For the rest see crocs.

> snakeypoos,

Bad fossil record, methinks, from the K.

> and lizards,

I only know circumstantial evidence about lizard extinctions. Archibald
counted that 30 % of terrestrial lizard species died out in NA. I'll have to
read The Age of Dinosaurs in Russia and Mongolia; its book review in Palaios
(2002, p. 304 -- 306, by Peter Dodson) says: "There was a major extinction
of Cretaceous lizard families, and only three families (Varanidae,
Isodontosauridae, 'Necrosauridae') are represented in the Paleocene of
Asia."

> multis...

Lost some (rather low) percentage of species in NA. The large Asian clade
Djadochtatheria didn't survive. That's all I know. Multi survival is
expected if multis can eat seeds, roots and suchlike (independence from
"green food chains".

> Currie writes paper
> called (something like) _What Extinctions?_

I'm waiting for it.

> Things-with-feathers-and-beaks-that-are-theropods
> -but-are-called-something-else-by-most, live.

Things-with-feathers-and-teeth-but-no-beaks-that-are-theropods are dead, all
and sundry. Things-with-feathers-and-beaks-and-teeth-that-are-theropods are
dead, too. Things-with-feathers-and-beaks-and-no-teeth-that-are-theropods
suffered greatly: Ornithomimosauria, Oviraptorosauria, *Gobipteryx* and
whatever other Enantiornithes, all gone. Only Neornithes survived, and
there's little evidence Neornithes was diverse in the Maastrichtian; most of
it wasn't widespread at that time in any case (that story about Antarctica).

> Monotremes.

May always have been rare... anyway, their fossil record is still very poor:
a total of 0 Late Cretaceous monotremes is known to date. The Paleocene has
yielded 1, *Monotrematum* from Argentina.

> It seems to me that the bolide people have it
> right, among terrestrial vertebrates the extinction primarily involved
> large creatures but not crocs.

Mmm... it involved all large terrestrial (not semiaquatic) vertebrates, lots
of small terrestrial vertebrates, almost all large marine vertebrates, and
lots of small ones again. Not to mention all those other animals, and
forams, and haptophytes... I think dinoflagellates too. Oh, yeah, and plants
didn't stay unscathed.

> Do you have new information on
> this?  Otherwise, why would I not be serious?

New... none that has been published since our last discussion, I think, and
little that I've read since then. :-)