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

Re: Long, long last gasp. (fwd)



> David M. says:
> >> For large oviparous animals this is suggestive of remote nesting sites
> >> with little or no predation-
>
> >or of less remote but well guarded nesting sites.
>
> True.  But I cannot think of a single mainland, winged animal that
practices
> this strategy, i.e., depends primarily upon defending its nest.

I cannot think of anything dead or alike that is remotely similar to Q.

> Further, Q. appears to me to be singularly
> poorly designed for nest defense!

Poorly designed? That giant animal? If it wacks you with 3 fingers, you're
going to fly from the Interior coast to the Pacific coast (or the other way
around, that depends). Sorry for my bad mood, but I think my point has come
across.

> >A _big_ impact is _not_ a local event. It has to produce
> bad flying weather _worldwide_.
>
> But the oceans are not bathtubs!  The Earth is not a sand pit.

And a 12-km meteorite isn't a gun bullet.

> >> By the way, how fantastic is it that some terrestrial
> >> birds are immune to the world's nastiest, fastest predators.  Ostriches
> >> foil predators that gazelles cannot.
>
> >Their camouflage is seemingly better, and they're better at running.
>
> And they avoid areas with trees, have head at good height for observing
> predator's approach, have terrific visual acuity...

... totally unlike cassowaries, which may not have been quite immune to
predation from marsupial lions, but, er...

> >> In the latest sally for molecules v. fossils, a recent mammal fossil
find
> >> (reported in a recent Science extended their evolution backward to the
> >> molecular estimates.
> >
> >Could you give me the citation?

Oh, that's what you mean! Nooo! That's _not_ a marsupial! It's the
_basalmost metatherian_! Have a look at the cladogram in that paper: there's
still no evidence for Marsupialia in the Mesozoic.

> >> How did modern birds survive those days when other birds with
> >> (probably) many similar niche requirements and morphologies didn't?
> >
> >- by apparently being in Antarctica, as far away from the impact as
> > possible
> >- by _not_ having similar niche requirements and morphologies as
> > those that did die out.
>
> Given that birds are effective dispersers, I think this is more an arifact
> of fossil record than reflection of reality.

The former: may well be. The latter: I can't imagine that all that easily.
Why shouldn't there have been niche partitioning?

> >> Bats are more likely avoiding getting whacked in the day light.
> >
> > How do you mean?
>
> Bats are easy targets for diurnal birds in the daylight--I don't think I
can
> find the ref. but some sinister researcher released bats in the daylight.
> They scrambled for cover but nevertheless many of them were hit by
> kookaburra.

So they could get whacked in the daylight -- but that's not enough evidence
to show that this is why they are nocturnal. (And how have we arrived at
this thread? :-) )

> >> OK.  For starters: birds are descended way more recently from
terrestrial
> >> animals than pterosaurs.
>
> >Yes, but why should the time factor be so important here?
>
> They diverged before advent of feathers.

Why should this so greatly impact their terrestrial locomotion? HP Jim
Cunningham tells us every few months that the maximum possible loads in the
skeleton of Q are not aligned with those of flight, but those of takeoff...
which strongly suggests they took off more than once a year, and that in
turn means they spent considerable time on the ground.

> >No -- the amounts of ejecta, and of nitrogen oxides etc.
> > produced in the impact, are easy to calculate.
>
> Sounds like famous-last-words!

So? Why? We don't need much additional data. For example, the temperatures
when dolomite and anhydrite vaporize (...or when calcium oxide does so)
under a pressure that can be calculated from the energy. It's a bit of work,
yes. Lazy and prone to miscalculations as I am, I'm not going to do it.
After all, it has already been done years ago.
        It's quite simple physics. I don't think you're going to need any
triple ring integrals.

> >- Q is known from very close to the boundary... your hypotheses require
> > that several totally unrelated extinctions all happened at the same
time.
>
> Who said anything about "unrelated"?  Birds affect pterosaurs,
> enantiornithines, and even (small) non-avian dinosaurs.

That's one. Then 2 out of 3 metathere clades in NA. Makes one more. Then the
ammonites, makes 3. And so on. I don't think you'd be able to keep the
number that low...

> "Similarly `Zhelestidae', an abundant element of Middle Asian coastal
plains
> since possibly the Cenomanian, gave rise to more derived archaic ungulates
> (`condylarths') in North America after arriving there in the late
> Santonian."
> From: Averianov, A O. , and J. D Archibald 2003 Mammals from the Upper
> Cretaceous Aitym Formation, Kyzylkum Desert, Uzbekistan. _Cretaceous
> Research_, Volume 24, Issue 2 , April 2003, Pages 171-191.

They shouldn't state this as a fact, AFAIK.
http://www.cmnh.org/dinoarch/2001May/msg00796.html I wonder when the
abstract I've reproduced there will turn into a published paper, but it
sounds like a good reason to think that the idea that zhelestids were
related to any part of the polyphyletic "Ungulata" is "the tooth, the whole
tooth, and nothing but the tooth".

> > > Yet when faunal interchanges occur species become extinct.
> >
> > Actually much fewer than you seem to think.
>
> Today's, observable, faunal interchanges wrought by Man...Zebra mussels,
> Nene, etc., etc.

Out of 1000 introduced species, 100 escape into the wild, 10 establish
themselves, and 1 or 2 become a problem in any way. Source? Two versions of
the lecture Introduction into Ecology. I'm talking about basic textbook
knowledge.

But _first of all_: Again: Evidence that such a faunal interchange happened,
please.

> >No. I want something concrete. When both *Cimolestes magnus* and
> >*Didelphodon vorax* (both badger-sized, the former eu-, the latter
> >metatherian) are present in the Hell Creek Fm and don't drive each other
to
> >extinction, yet are supposed to have died out due to the immigration of
> >something else, then I must know what that something is supposed to be.
>
> Like yours, mine is a timing thing.  Invasions occur, community structure
> changes.  And it doesn't have to be a justice issue (i.e., which species
> _deserves_ or has the better qualities, etc.).  When EO Wilson fumigated
> small mangrove islands, the same number of insect species
recolonized...but
> they were different species.  Similarly, we see major adjustments in
> community structure in countries that are invaded, e.g., Australia.

You haven't answered my question: what that is known in the fossil record
could have outcompeted *Cimolestes* and *Didelphodon*?