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

Re: Science News etc

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?

> 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.

> 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?

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

> 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.

> 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."

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?
(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.

Besides, I'd appreciate answers to more of the questions I asked in my 16.5 
KB post. Don't worry, I can wait... but sooner or later I'll assume you don't 
have answers.