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Re: From Science New, and synonymous sauropods



Original Message by Tim Donovan Monday, 11. November 2002 13:19 

> >On Sun, 10 Nov 2002, John Bois wrote:
>
> > I only meant to say that the study of dinosaurs is appropriate
> >(for all we know) for the the study of dinosaur's extinction
>
>    Right.

It is of course not totally irrelevant, because it contributes to the whole 
picture. But it alone cannot replace the rest of the whole picture. After 
all, not only dinosaurs died out; dinos made up a pretty small percentage of 
the victims.

> Note the loss of some diversity about 2 million years before the
> end, which suggests another factor causing a preliminary extinction.

Some have suggested that there was a little mass extinction in the 
mid-Maastrichtian, totally unconnected to the K-T. I don't have enough 
literature on it. Note that the Hell Creek Fm is not the entire world, any 
change in dinosaur diversity there may or may not reflect a change in global 
dinosaur diversity.

> > --this is true
> >whether or not some massive force hit.  For example, what was it about the
> >dinosaurs that made them susceptible and not other living things?
>
>     You mean many other living things.

And _I_ mean damn few other living things. Benthic foraminifera went through 
pretty unscathed. Pretty much everything else of which we have fossils was 
hit. Not everything equally severe... but remember that one surviving 
population can be enough to let a species and thereby potentially a big clade 
survive, so random comes in here.

Dalila Zaghbib-Turki, Narjess Karoui-Yaakoub, Rakia Said-Benzarti, Robert 
Rocchia & Éric Robin: Révision de la limite Crétacé-Tertiaire de la coupe 
d'Ellès (Tunisie): Proposition d'un nouveau parastratotype, Géobios 34 (1), 
25 -- 37 (30 June 2001)

Apart from a shortened and slightly confusing abstract, this paper is in 
French. Try to get a look at it in any case because the figures speak for 
themselves.
        Page 33 for example. The specific diversity of planktonic forams is 
almost 
constant in the last 3 m of Cretaceous sediment; in the last centimeters it 
rises a little, probably due to intensive collection. It surpasses the number 
of 35 species at the K-T -- when it drops _straightly_ _at a right angle to 
the time axis_ down to _one_ species. Within the next meter it rises to over 
20 again and then stabilizes between about 15 and 20.
        P. 29 shows the data used to plot this: the distribution of every 
species of 
planktonic foram in the stratigraphy of the site. More than a third is found 
the last time at the K-T boundary. A slightly smaller number dies out within 
the next meter, which is when a similar number appears first. Only three 
species die out within the last four meters of Cretaceous; only two new ones 
appear in these layers (both survive far into the Paleocene).
        P. 31 shows the temporal distribution of benthic forams from the same 
site. 
First appearances cluster within the 2 m around the K-T, but not a single 
extinction happens then. (That came at the Pal-Eocene boundary.)
        All this probably says something about the event. What about a 
Strangelove 
ocean: the surface waters suddenly became acidic, then cold, then hot. That 
should do a lot of plankton in but shouldn't harm the benthos.
        The stratigraphy in Ellès is better resolved than that in the K-T 
stratotype, El Kef. It might become the new stratotype.

> Dinosaurs were supposedly more
> vulnerable because of their prodigous food requirements at a time of energy
> depletion.

By their size in general. Apart from food requirements it prevented them from 
sheltering from ejecta, fire and acid rain, and it made them susceptible to 
the impact itself, means, the corresponding humongous earthquake. It fits 
neatly that all terrestrial (not semi- and aquatic) animals over about 25 kg 
died out.
        Any division between "winged" and "wingless" dinos is probably 
meaningless 
here. The great diversity of flying theropods -- long tails, short tails, 
alulae or not, teeth or not... --, not to mention that of secondarily 
flightless ones, whichever these are, was cut down to a sad meager bunch of 
Neornithes.

> The initial proliferation of ferns while the dust was settling rules out
> freezing temperatures and darkness. [...] Modern analogs
> of the K-T fern species, including a tree fern, require full sun to make
> spores, which are present in the upper impact layer.

Have you, HP Tim Donovan, at last read the Science paper on the fern spike in 
NZ? I sent you the pdf, didn't I? (If it hasn't reached you, please tell me.) 
Because there it says that the tree ferns formed the very last stage of the 
fern spike. Nobody suggested that the ferns overgrew the world _while_ it was 
dark and cold. The idea is that the ferns took over some months or maybe 
years after the impact, when light and heat had come back (the latter 
enhanced by the impact-induced greenhouse effect) and before angio- and 
gymnosperms had reacted.

Just two weeks ago I've seen big fern meadows in the Alps (grass 10 -- 20 cm 
high, ferns 50 -- 100), covering maybe several square km. Normal meadows like 
the neighboring ones, except that almost all the visible vegetation consisted 
of ferns. I don't know how they were caused, but they show that a fernland is 
possible even in the presence of fast-growing angiosperms that didn't exist 
at the K-T.

>   Ordinarily the replacement of angiosperms and conifers with ferns would
> probably doom the dinosaurs since ferns aren't energetically rewarding.
> Tree ferns requiring full sun may well have been different.

Is there anything except insects that eats tree fern leaves?

> In any event
> recent research suggests only 10-20% of the biomass burned,

Only? ONLY?!? Isn't that equivalent to burning the leaves off _every tree_?!?

> which implies widespread survival of "good" vegetation

Isn't the marine biomass, which obviously didn't burn, contained in the above 
figure?

-----------------------------------------
So there is a little evidence that *Opisthocoelicaudia* and *Nemegtosaurus* 
cooccurred. This makes it more probable that they were the same, but that was 
it, IMHO it doesn't resolve anything. Considering Jurassic and EK sites 
around the world, is there anything strange about 2 species of sauropod in 
the same place & time?