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Re: Combined answer 2 Re: The extinction of small dinosaurs (fwd)



Date: Fri, 13 Dec 2002 22:27:46 +0100
From: David Marjanovic <david.marjanovic@gmx.at>
To: dinosaur@usc.edu
Subject: Combined answer 2 Re: The extinction of small dinosaurs

> Fish were hurt. We've had that discussion onlist.

I'm curious as to what fossil find you would accept as falsifying the
bolide--I mean, if fish did swimmingly, despite the energy pyramid being
knocked from underneath them, this should present a problem.  Yes, tropical
species could be restocked from places where the post-bolide effects are
thought to be milder?  Is there a way to falsify this?  Just to set a
base-line...if one known tropical species swam right through the K/T, would
that do it?

>> Except for...wait for it...mammals,

>Remember the diversity of Eutheria before (especially, but not only, in
Asia)
>and after, for example. You yourself have talked a lot about the
metatherian
>extinctions.

They're not extinct.  We're in a global context, right?

>> insects,

>>"...It is hypothesised that the global disaster [...] led to an extinction
of
>>most Raphidioptera, in particular also of all those species (genera,
>>families) which were adapted to tropical climates. Those species (genera,
>>families), however, which were adapted to a cold climate could survive..."

But are you arguing that all insects were restocked from arctic survivors?
Or are you saying that every survivor had some sort of acid-rain resistant,
firestorm-resistant, tsunami-resistant strategy.  Again, how would you know
you are wrong--what finding would you accept as falsifying the
bolide-as-cause-for-everything hypothesis?

>> One of the talks at the last SVP addressed this point and found: no
>> evidence of a bottleneck in birds.

>Was that the one about the Neornithes of Antarctica? (Looks pretty bold to
me
>to refer an isolated tarsometatarsus to Burhinidae. Well.) If so, it was no
>evidence of a bottleneck, but neither was it evidence of no bottleneck. :-)
>Would be great to find a lot more Enantiornithes from the Maastrichtian,
for
>example.

The talk I was referring to was:

WAS THERE A BOTTLENECK IN AVIAN DIVERSITY AT THE END OF THE CRETACEOUS?
DYKE, Gareth J., Department of Zoology, University College Dublin, Belfield,
Dublin,
4 Ireland; CHIAPPE, Luis, Natural History Museum of Los Angeles County, Los
Angeles, CA 90007; DORTANGS, Rudi, JAGT, John, and SCHULP, Anne,
Natuurhistorisch Museum Maastricht, Maastricht, NL-6200 Netherlands.
...and it concludes: "Range correlations of lineages of Cretaceous birds,
combined with gap analysis and the estimation
of clade confidence intervals shows that there is little evidence for a
'bottleneck' in
diversity at the K-T boundary."

Again, I'm curious.  Is the hypothesis falsified if an enanti were found in
the Paleocene?  Would it make a difference if it were discovered that these
birds survived?  Probably not, right?  You would then just set off looking
for hibernation in enantis, or resort to the idea that the killings were
random and more neos survived out of luck.

>So you missed the discussion with HP Tim Donovan (began with the subject
"How
>Did Hadrosaurs Survive?")? There is a fern spike in the USA, New Zealand
and
>Hokkaido.

This hurts.  I'm tempted to cry uncle.  But, how does this affect your bird
refugium hypothesis.  If the atmosphere was just as toxic in the south, how
did birds survive it?

>Maybe everywhere else all birds were killed, and in Antarctica a
>few that happened to be neos managed to survive.

That must be it.  

>> (There are)  _many_ possible adaptations (that neornithines might have
had)
>> that could make life miserable for sedentary dinos (and/or pterosaurs).

>Before you propose the next one, ask yourself "why doesn't this produce a
>mass extinction right now"?

Different organisms are good at doing different things.  A possible model
for pterosaur/bird competition is bat/bird competion.  Birds--generally
speaking--rule the day; bats the night.  I know we discussed  this--but
perhaps a new idea might crop up this time.  Bats are probably susceptible
to predation by diurnal flying things (birds).  _And_ because they don't
need a flat surface to put an egg, they are not in competition with birds
for (particularly) caves.  Pterosaurs went head to head with birds.  I
believe birds were the superior competitor.  It's _OK_ to be
superior.