Re: "But What About The..." arguments (longer again...)

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

----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Friday, June 07, 2002 5:50 AM

> > > But mine is more parsimonious
> > > since, a) competition/predation are observable phenomena and are in
> > > operation today;
> >
> > That doesn't mean anything. That we can't observe a teraton impact, a
flood
> > basalt eruption or a running animal that weighs 5 tonnes doesn't mean
that
> > never happened, too bad for Lyell. The present is not the key to the
past.
> > The past is the key to the present, and to the future.
>
> Not the point.  I'm not arguing that bolide couldn't have caused
> extinction.

But you argue that supposedly observable phenomena should be considered
first and foremost, don't you?

> I'm arguing that the pattern of extinction attributed to
> bolide has not been articulated/explained to my satisfaction.

The impact can explain why nautiloids survived and ammonites didn't; why
everything terrestrial heavier than 10 kg or so died out; why the plankton
was decimated so extremely; why it all went so fast
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1209000/1209870.stm; why
herbivorous insects (respectively their bite marks on fossil leaves) were
decimated so much; why Raphidioptera (snake flies = camelneck flies) was
such a widespread group in the Mesozoic why today the group is rare,
restricted to northern temperate latitudes and needs frost for development
(all that didn't died out); maybe even why the ground-living and
shorebird-like early Neornithes survived while arboreal Enantiornithes
didn't, but too few LK birds are known in the first place to confirm this.
What else do you need?
        (The only known enanti from the Hell Creek Fm, *Avisaurus*
www.dinosauria.com/jdp/misc/hellcreek.html#dinosaurs, was arboreal; if we
ignore that "lori" jaw, I can't think of an arboreal neornithine from the
entire K.)

> One we like--because we see
> it all the time--is competition/predation.

I repeat: You don't see it all the time.

> >         Wait. Competition is _hardly_ observable. The ghost of past
> > competition, as niche partitioning is called, is very easily observable,
on
> > the other hand.
>
> Right.  _And_ the continuous replacement of species by better competitors
> throughout the fossil record.

No, this is not so easily observable in the fossil record. In the past the
survivors of every extinction were a posteriori proclaimed to be better
competitors... that's changing.

> > > If neos did ascend via competition, myriad possibilities
> > > exist for how, [...]
> >
> > Then go on and make a testable hypothesis out of that.
>
> As if, right?

As if what?

> But the principle is very sound.  I mean we're back to the
> effectiveness of competition from invaders in disrupting contemporaneous
> communities.

There's a paper in this week's nature (abstract for free for subscribers:
Biodiversity as a barrier to ecological invasion
THEODORE A. KENNEDY, SHAHID NAEEM, KATHERINE M. HOWE, JOHANNES M. H. KNOPS,
DAVID TILMAN & PETER REICH
http://www.nature.com/nlink/v417/n6889/abs/nature00776_fs.html)
that says invasion of plants into an ecosystem is not nearly as simple as
thought.

There's an SVP meeting abstract (gotta find it...) that says the Central
American landbridge was already open IIRC 9 Ma ago, but covered in
rainforest, so only tapirs, procyonids etc. could invade, and they stayed in
the rainforest instead of conquering Argentina's rich fossil sites. (This
eliminates the need for an overseas dispersal of procyonids proposed
earlier.)

> > And nowhere since... looks like I don't need that 40-year-old paper. In
> > addition, I'm sure Van Valen only looked at NA, or only at the Hell
Creek,
> > and didn't know about the current concepts of therian phylogeny. [...]
>
> It's a landmark paper. Sloan and Van Valen. (ref. if needed)  It would be
> good to hear a specific rebuttal.

OK, then please give me the ref. Could someone else please enter this
discussion? :-)

> The
> fact of its being 40 years old doesn't signify.  Using this logic I should
> wave off my students from Darwin because it's over _140_ years old.

Some parts of what Darwin wrote are indeed outdated. Just look at his
speculation about how inheritance worked -- absolute nonsense. No wonder, he
didn't know about DNA and stuff.

> And, by
> the way, I forget where I read it--might have been Currie--saying the same
> guild is found earlier in more Northern parts (i.e., Canada).  Do you know
> about that?

No. I also don't know how this could be correlated to the availability or
quality of sites or simply be outdated by more recent finds or whatever. --
Current knowledge of Asia's K mammal faunas does make it unlikely that said
eutherians came from Asia... and competition fully fails to explain why
Asia's stagodontids, the deltatheroids and Asia's basal eutherian clade
didn't survive, we've been through that.

> In any case, they had to come from somewhere--unless you are
> saying the replacement didn't happen.

What I'm saying is that the impact removed most of NA's metatherians and
allowed the eutherians to take over afterwards.

> > All discussed over and over onlist. I think your point is thoroughly
> > defeated.
>
> Which point, the recent asymetrical exchange of placentals south and
> marsupials north;

Do you mean the American Interchange? SA's marsupials are largely unable to
cross the rainforest or to come out of it. Sparassodonta was apparently
extinct before the interchange, and all others (Argyrolagidae...) were
extinct long before it.

> the almost complete domination and destruction of many
> Oz
> niches (Oz conservation journals are full of this stuff!) by placental
> invaders--bunnies, cats, dogs;

Now the difference to Maastrichtian NA is that in the latter eu- and
metatherians were _coexisting_ for quite some time. *Didelphodon* and
*Cimolestes* are AFAIK found in the same layers, not *D.* first and *C.
afterwards.

> or the almost total
> elimination of marsupials from most continents (Africa, Europe,
> Asia, North America vs. Oz and SA

You are overlooking the fossil record of Metatheria from the Paleocene to
the mid-Miocene. There are metatherians everywhere, NA, Europe, Asia, and
they even invaded Africa. Have a look at
www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Synapsida/M
etatheria/Boreometatheria/Herpetotheriidae.htm and
www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Synapsida/M
etatheria/Notometatheria/Peradectidae.htm, all of them Cenozoic. (The
higher-level taxonomy is another issue... Boreometatheria is paraphyletic,
and Peradectidae now includes the K Alphadontinae which are not
Notometatheria.) And now the opossum (a crown-group marsupial, different
from all I just mentioned) has invaded NA.

> Re: pterosaurs
> > Whatever happened, it happened long, long before the K-T boundary and so
has
> > nothing to do with it.
>
> This is certainly not true if birds did the deed.  Because, if they did,
> they could have also done other deeds--deeds that _are_ attributed to K/T
> event.

Wouldn't be positive evidence, though, and would even less be evidence that
the impact didn't do it.

> For sake of speculation, what if a raptor-like bird evolved (not
> far-fetched).

I don't know if this is far-fetched. The only known raptor-like bird from
the entire Mesozoic is the EK enantiornithean (not neo, BTW...) *Boluochia*.

> This could have instantly eliminated many creatures.

Impossible. Said creatures would adapt to its presence while it evolves.
Except if it evolves on a small enanti-free island and then invades the
whole world without leaving fossils so far (the oldest known fossil raptors
are Eocene, aren't they?).

> What
> was that a little while ago: molecular evidence places divergence of
> falcons and hawks (?) pre K/T.

Molecular evidence places the divergence of everything and anything pre-K-T.
So much that I don't trust it.

> > > Have we finished with the eggs in China, and the hadrosaur bone in SW
> > > NA?
> >
> > Yes. The former simply occur below Paleocene mammals, and the K-T
boundary
> > is not preserved. :-) The latter has been contended onlist repeatedly.
>
> The former, I thought, did have a boundary signature (Ir) _below_ the
> shells (like India, perhaps?).

I have a recent paper (Vertebrata PalAsiatica) on such a site somewhere,
I'll look that up.

> Re: India
> > Ah, so they say the boundary layer is below the boundary in that place!
> > Very, very strange, as it is _at_ the boundary _everywhere else in the
> > world_.
>
> Do you smell a rat?  Or a smoking gun?

All I smell is strangeness, because everywhere else I know of, and most
other people seem to know of, the Ir-rich layer is the K-T boundary. Before
I shoot around accusations such as reworking, a defect mass spectrometer,
incorrect identifications of fossils or whatnot, I'll have to see the paper
or a good summary.

> > > low and declining diversity of ammonites
> >
> > Wrong.
> >
> > > and their turtle friends;
>
> > Sure?
>
> See Ron Orenstein's recent posts.

In which he formulated that as a question (nobody answered) and IIRC didn't
mention turtles. Again, I have a paper buried somewhere... I'll certainly
find something over this weekend :-)

> > > slight relaxation
> > > in size constraints for pre-K/T mammals (in NA, at least);
> >
> > *Repenomamus*! *Gobiconodon*! *Kollikodon*! All EK.
>
> Compared to any known eutherians, there was a relatively sudden, slight
> relaxation of size constraints among the latest K taxa (whose first name
> was Ralph).

So what are you arguing? Any or all of the below?
- triconodonts and monotremes somehow unable to predate nests or whatnot,
eutherians being capable of doing so, and of outcompeting stagodontids, but
only with a delay of some Ma
- *Cimolestes* and *Didelphodon* being statistically significant
- the abovementioned 3 not being statistically significant
- the fossil record of Mesozoic mammals being good enough in the first place
- knowing the exact size constraints in the first place

And wait, I forgot some more big & dangerous Mesozoic mammals...
Deltather-your-favorite-ending-here is not limited to the LK of Asia.
They're apparently not that big, though... I can't find the size of
*Atokatherium*: http://home.arcor.de/ktdykes/basmeta.htm (scroll down a
little).