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Re: Nocturnal crocs?



----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
[...]
Sent: Saturday, August 25, 2001 9:40 PM
Subject: Re: Nocturnal crocs?


> On Sat, 25 Aug 2001, David Marjanovic wrote:
>
> > > I have said there are no data supporting either case.
> >
> > Wrong. There is the impact and evidence for all its consequences (forest
> > fires, acid rain, tsunami, and whatnot). I'm too lazy at the moment to
> > repeat what has been written onlist since 1994.
>
> This is data for a bolide, not extinctions, and definitely not
> for _patterns_ of extinctions.  I grant you that it gives a
> strong scenario for dino extinction--but not birds.  And you
> can't sya that because it killed non avians it also killed
> avians!

Wait a minute. Global forest fires etc. are _catastrophes_, they will _kill
off_ everything that isn't hidden somewhere. Evidence for such impact
consequences is direct evidence for a mass extinction. Not to mention here
B-) that there _was_ a mass extinction in pretty much all ecosystems.

> Remember, the fossil record is totally
> mute on this issue--the timing, the means, the death toll--nothing.

The timing? Hadrosaur footprints 37 cm below, in one word _at_, the
boundary. The means? See above. The death toll? Pretty well represented in
the fossil record: over half of everything.

> > ...whereas your evidence is: *Stagodon* and IIRC *Cimolestes* in the
same
> > place at the end of the K, as opposed to *Deltatheridium* and the Gurlin
> > Tsav skull* in the ?Campanian of Mongolia and *Gobiconodon* in the late
EK
> > of Mongolia and North America. (I'm leaving out the multituberculate you
> > mentioned because it may have been purely herbivorous, and
> > *Repenomamus/-nus* because know next to nothing about it.)
>
> You might be able to leave it out on grounds of diet (however, _many_
> sp. whose diet consists of plant material are also fab egg eaters), but
> you can't as evidence of size increase.
>
> > > My mechanism
> > > is not a "holocaust" at all; it is a slow, steady, abiding selecetion,
> >
> > ...beginning in the EK with the appearance of cat-sized mammals? Such a
> > gradual extinction is a lot too much for me.
>
> I'm not saying that.  I am saying that mammals were tiny for most of the
> Cretaceous--with some exceptions--and then there was an increase in mammal
> size just before dinos became extinct.

Well, I say that 2 or 3 of these exceptions happened in the late
Maastrichtian. Just a fluke of the fossil record.

> That is either true or
> not.  Lillegraven thought it was true.  Even John Alroy's data show an
> increase--though more modest, of course than post dino times--in mammals
> size immediately pre K/T.

Can I have some statistically significant details?

> > The present is not the key to the past. The past is the key to the
present,
> > and to the future.*
>
> I would say this was not a biologist's statement.  Much of what exists
> today, existed since life began.

AFAIK James Lawrence Powell is a... drum roll... _paleontologist_. Some
things, like flood basalt volcanism or giant impacts, have happened at
certain times in the past and will happen again, but coincidentally there is
none happening right now.
Neontologists are practically creeping on the 3-dimensional "surface" of the
enormous 4-dimensional "volume" of deep time.

> > It is well
> > possible that all birds died out everywhere else and a few managed to
> > survive in Antarctica.
>
> Hardly.  For such an unlikely scenario to be true, so must the
> following: neos outcompeted enantis nowhere else but
> Antarctica.

nope
what about: all enantis died out and nearly all neos died out -- survival of
the luckiest
what about: all Antarctic enantis bred on trees, and all trees burnt down

> OK, if it were some ground-bound beast we could
> understand--isolation would be enough.

Antarctica wasn't isolated but connected to SA and Australia.

> > > Phorusrhacids evolved amid grasses.
> >
> > Stop -- wrong. Phorusracoids evolved in the Paleocene, means, before
> > grasslands. They are known from IIRC Eocene France (*Ameghinornis*) and
> > middle Eocene Messel (an AFAIK unnamed skull).
>
> The biggest Phorusrhacids in grass--this is from Marshall.  What size are
> the sp. you're talking about?

I don't know, but if they were exceptionally small, someone would IMHO write
it in a book I have read.

> > > Diatrymids may have depended upon
> > > wetlands,
> >
> > How so? Apart from looking more like phorusracoids and tyrannosauroids
than
> > like, erm, flamingos, they had a pan-Laurasian distribution (*Gastornis*
=
> > "*Diatryma*" in NA and Europe, *Zhongyuanus* in China).
>
> Gastornithids existed while NA and Europe were covered with
> wetlands.  When each continent drained, they disappeared--thopugh the
> draining occurred at different times on each continent.

- No continent was ever "covered with wetlands". That's just geologically
and climatologically impossible.
- The Thule landbridge (produced by the flood basalts associated with the
birth of Iceland) can't possibly have been "covered with wetlands".
- Gastornithids died out at the Eocene-Oligocene boundary, along with
pristichampsid crocs and lots of mammals (including the multituberculates).
Craters are known...

> > > a mammalian refuge
> >
> > ???
>
> In modern swamps, predator access is increased when water level is
> lowered.  Predator density is
> greater in uplands surrounding wetlands than in the swamps themselves.
> (Can cite both of these).

OK, true, but see below:

> > > which was in short supply at the terminal Cretaceous.
> >
> > when the regression turned the Western Interior Seaway into one huge...
> > wetland. Please correct me if I'm wrong.
>
> Archibald (1996) says that they lost alot of their prime habitat--I
> assumed...

I hope you didn't assume that all or most dinosaurs lived in western NA
wetlands!!!

> > > > But I would argue that their wasn't really any "size relaxation" in
the
> > > > K/T.  Merely a better represented fossil record.
> > >
> > > Then we have competing hypotheses.  But I have positive evidence, you,
> > > only negative.
> >
> > Your positive evidence is, see above, 2:1:1, maybe 3:1:1. I won't call
that
> > "evidence".
>
> No.  It _is_ evidence.  Not of the quality you like perhaps.  And not
> convincing, true.  But it is supportive.

It is _not_ evidence unless you show that it is statistically significant --
for which you would surely need a much better fossil record.

> > > > And Ostriches aren't anyware near as predatory as some of the
> > > >dinosaurs.  If a modern day jackal tried to drive a dromaeosaur off a
> > > >nest, it would be merely dinner.
> > >
> > > Only if it could _see_ the jackal.
> >
> > 1. Any reason to suppose the contrary?
>
> Yes.  See earlier citation--or ask me for it.

(thanks, but I'm quite sure the paper would be inaccessible here)