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Re: Science News etc




From: David Marjanovic <david.marjanovic@gmx.at>
Reply-To: david.marjanovic@gmx.at
To: dinosaur@usc.edu
Subject: Re: Science News etc
Date: Fri, 15 Nov 2002 12:07:12 +0100

Original Message by Tim Donovan
Wednesday, 13. November 2002 12:42

> It is hard to be sure if the Lancian fauna was really stable. Edmontonia
> may have disappeared hundreds of thousands of years before the end,


Evidence please? And how common is it farther down -- could the Signor-Lipps
effect have struck again?

It disappears 200m below the boundary in the Ferris (unpublished data) and is common farther down.



> and few large taxa were common.

And once more, we need to talk about the whole world, not just about the
coastal plains of western NA.

It was there that the problem, or an important part of it, originated, in my view.

> The discovery of very large edmontosaurs and T. rex > specimens suggests a continuing "arms race". (UCMP 118742 was found > stratigraphically high).

How many specimens are there so that you can make a statistically sound case
for such a trend?

I'm awaiting more data.

> At sea the case for gradual extinction within the > late Mastrichtian is better.

Hm. It isn't for forams and haptophytes. Nor is it for mosasaurs and
plesiosaurs. I don't know the ammonite literature, but I'm under the
impression that the longer people look at the fossil record, the more
catastrophic it looks.

As Dodson noted in THE COMPLETE DINOSAUR, some have been found at the boundary but the bulk still seem to disappear before it.



It isn't sure what, if anything, happened to rudists
in the mid-Maastrichtian, but in any case most groups survived to the end.
(I've seen late Maastrichtian cf. aff. *Hippurites* in person. :-) )

>   Some hypsilophodonts -Atlascopcosaurus IIRC -

Several more.

> lived at high latitude and
> were probably capable of hibernating, which meant that shelter was
> available and they could endure a scarcity of food.

I'm not sure what to think of the LAGs; they're supposed to be caused by
internal clocks, not the environment, and are generally uncommon in
ornithischians... anyway, they are end-Early Cretaceous. Didn't the area warm
up later?

Even if it did, there'd still be loss of productivity in winter.

And would all those animals have endured a winter at the wrong
time, plus wildfires, plus acid rain, plus the greenhouse effect afterwards?
Not to mention the tsunami which should have crossed the Pacific in not much
more than a day.


> I doubt any birds were as well off.

Right. You see, almost all died out, as far as the poor fossil record allows
to tell.


>  Stidham et al wrote that Neornithines were already
> proliferating at the expense of Enantis in the late Maastrichtian, and
> diversifying.

All I know by Stidham is that famous lower jaw that looks like it could be
referred to a part of the crown group of parrots.

He mentioned several Neornithine groups which were already present in the late Maastrichtian and therefore survived.



Did he really write "at the
expense of Enantiornithes"?

He indicated they had become dominant or more numerous, although enantis are known.


I can't imagine that because how many
Maastrichtian enantis are known?

> Under the circumstances, survival of several Neornithine
> lineages is remarkable considering their disadvantages compared to certain
> high latitude dinos, under hypothesized impact conditions.


It isn't more remarkable than that of several lineages of Theria.

They had burrows. Small dinos probably could find shelter too. Birds were probably the most exposed to debris, fire and smoke etc. If they could survive it some dinos should have too.



> The proliferation of fern species requiring full sun to make spores was > already underway within weeks of the impact, according to Arens.

How can anyone tell? A real question, not a rhetoric one. It's just a problem
that you throw out various opinions without giving the evidence or any ref
apart from the occasional author's name.

I'm not sure of the original ref-Sweet?- but Arens is at the forefront of this research.

> Such species were already more abundant > in the upper impact layer than they were prior to the impact.

I think that depends on the definition of "impact layer". Once more a
sentence from the Science paper I mentioned:

"The fern spike (of both ground and tree ferns) extends into the upper part
of the earliest Paleocene *Guembelitria cretacea* foraminiferal zone (P0) in
the mid-Waipara and Hokkaido marine sections (15, 17), implying a duration of
~ 30,000 years."

What I mentioned is from the Hell Creek; she said ferns requring full sun to make spores were already doing this within weeks of the impact. So much for "night comes to the K."

Refs (I haven't read either): 15: C. P. Strong, N.Z. J. Geol. Geophys. 27, 231 (1984) 17: T. Saito, T. Yamanoi, K. Kaiho, Nature 323, 253 (1986)

What is your evidence that phase iii of the fern spike began to be deposited
after just a few weeks?

This was supposed to be the very first phase.

(Oops, the "freeezing ground temperatures" I quoted for phase i are my typo.
:-] )


> Their ability to experience an "ecological release"
> indicates that there was adaquate sun and generally benign conditions.

During the greenhouse effect. After most K-T victims had already died out.

But the apparent lack of an impact winter casts some doubt on the lethality of the event, just like the survival of birds. This suggests other factors were involved; so does the decline of vegetation, such as angiosperms, immediately prior to the end.

Besides, I'd appreciate answers to more of the questions I asked in my 16.5 KB post.
 I must have forgot them.

Don't worry, I can wait... but sooner or later I'll assume you don't
have answers.


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