[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Nocturnal crocs?



> On Sat, 25 Aug 2001, Morgan Churchill wrote:
>
> >> Until
> >> it is something more, something that is supported by data, the
> extinction
> >> hypothesis for birds must line up and take a number.
>
> >this strikes me as very selective reasoning; you argue that thier is
> >not much evidence to support a mass extinction of birds at the end of the
> >Cretaceous, but you hold to a belief that a mammal egg predation
> >holocaust, which if anything has even less to support it, did happen.
>
> 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.

> In the meantime, my
> beliefs are, I would argue, as roughly supportable as yours.

...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.)
*may have got a name in the meantime, was unnamed in 1998

> 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.

> a
> selection which operates strongly today (at least this claim is supported
> if not known).  Your claim has no observable phenomena, no
> precedent.

The present is not the key to the past. The past is the key to the present,
and to the future.*

*quoted or slightly paraphrased from "Night Comes to the Cretaceous"; I was
unable to find the exact place again

> Yes, there was a bolide, but, again, what magic-bullet effect
> can account for selective bird extinction.  I mean the big dinos can
> starve due to no food.  What about the little birds?

"No food" -- that's just _one_ problem. There was the whole apocalypse.
Regarding food -- small insect-eating birds can survive because insects just
never die out, and seed-eating birds can survive too. _Leaf_-eating and big
carnivorous birds would starve, but as far as known there were no such birds
in the LK. And remember, it was recently mentioned onlist that Antarctica,
far away from both Chicxulub and the _possible_ Shiva crater
(India-Seychelles), had only Neornithes among its LK birds. It is well
possible that all birds died out everywhere else and a few managed to
survive in Antarctica.

> >> The question then is: at what point in nest and
> >> hatchling predator evolution did this first become true (if true)?

Now we need to know the fossil record B-)

> > Haven't they though?  the Phorushacoids of south america are pretty
> >close to being a "re-evolved" dinosaur predator.  These birds not only
> >competed well with mammals, but actually entered North America when the
> >two continents were bridged.  Their were also the Diatrymids.
>
> 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).

> 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).

> a mammalian refuge

???

> 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.

> > 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".

> > 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?
2. We're not talking of jackal-sized mammals, but of cat-sized ones.