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

[John Bois <jbois@umd5.umd.edu>]

On Thu, 6 Jun 2002, David Marjanovic wrote:

> > Evidence is enantis disappear and neos diversify.  Note: this is the same
> > evidence for your preferred hypothesis.
> 
> Yes. Question is when that happens, and I'm not sure the fossil record is
> good enough at the moment to test who's wrong here.

It's not!  That's one reason I haven't declared a winner.

> > 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.  I'm arguing that the pattern of extinction attributed to
bolide has not been articulated/explained to my satisfaction.  Therefore,
I and many other of the judges still allow competing hypotheses.  One  we
like--because we see it all the time--is competition/predation.  We
especially favor this for birds.

>         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.

> > If neos did ascend via competition, myriad possibilities
> > exist for how, including: behavioral advances, reproductive advances,
> > flight characteristic advances, etc., etc.

> Then go on and make a testable hypothesis out of that.

As if, right?  But the principle is very sound.  I mean we're back to the
effectiveness of competition from invaders in disrupting contemporaneous
communities.

> 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. Where is
> that Asian clade of Eutheria, where is Deltatheroida in the Cenozoic? Where
> are the Asian members of Stagodontidae? Where are *Asiatherium* and
> *Marsasia* (OK, the latter IIRC is Coniacian)? Are there any palaeoryctids
> (like *Cimolestes*) or leptictids (like *Gypsonictops*) in K Asia? I don't
> know of any. If there really weren't any, said groups can't have immigrated
> from Asia to NA.

It's a landmark paper. Sloan and Van Valen. (ref. if needed)  It would be
good to hear a specific rebuttal.  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.  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?  In any case, they had to come from somewhere--unless you are
saying the replacement didn't happen.

> > All sorts of reasons why marsupials may have
> > fared better in some places rather than others...
> 
> 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; the almost complete domination and destruction of many 
Oz
niches (Oz conservation journals are full of this stuff!) by placental
invaders--bunnies, cats, dogs; or the almost total
elimination of marsupials from most continents (Africa, Europe,
Asia, North America vs. Oz and SA

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.  For sake of speculation, what if a raptor-like bird evolved (not
far-fetched).  This could have instantly eliminated many creatures. What
was that a little while ago: molecular evidence places divergence of
falcons and hawks (?) pre K/T.

> > 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 don't believe this has been fully
revealed to the list and I
have been unable to acquire the paper--what are the issues, here?  The
latter?  The guy was going to do a presentation--then he disappeared.  Is
there still something in the works?  Throw me a bone, here, somebody.

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?

> > low and declining diversity of ammonites
> 
> Wrong.
> 
> > and their turtle friends;

> Sure?

See Ron Orenstein's recent posts.

> > 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).