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Re: What really happened 65 Ma ago (not a joke)



John Bois (jbois@umd5.umd.edu) wrote:

<It's not so much that I ignore other extinctions, it's just that birds
are a good test for inclusive hypotheses, i.e., explanations that seek to
include every clade in an instant biotic turnover.>

  If this is used to explain the extinctions at the end of the Cretaceous,
as one has used other seismologic and catastrophic scenarios to support,
it MUST include theories on the extinction of OTHER animals, and tests of
biodiversity declines and competitive regimes as has been theorized. He
hasn't done this. Focusing on dinosaur diversity, pterosaur diversity, and
the so-called pterosaur deficiency of flight relative to birds and their
competitiveness, ignores the terrestial non-dinosaurs and the marine
realm, all vastly important given the theories on global extinctions.
Thus, no testing on specific models has been done, only using small sets
of data to support generalist theories. Like saying an earthquake effect
with resulting tsunamis, and then going global to find an earthquake
source for all tsunamis on record -- it ignores other variables at play,
including landslides, relative earth movement, or any other effects that
might cause such a vast displacement of water.

  So ... the bolide would not kill except at the point of its entry into
the crust and the region it srikes. Everything else that dies is
_corrollary_ from flashfires, acid rain, tsunami, catalyzed volcanism,
global weather and ocean current shifts, aerial and aquatic chemical
introduction, etc.

  ...

  And while I was writing this, I came up with an odd idea and am
proposing this for the sake of curiosity:

  Pterosaur competition with birds. In the Jiufotang Formation of Liaoning
Province, we see an incredible diversity of enantiornithines, some
ornithurines, some non-ornithothoracean birds, and a few pterosaurs. Why?
If they are as aerially abundant, why wouldn't a catastrophic event hit
them equally? One should see pterosaurs and birds hit if they were all in
the air at the same time. Why should the differential preservation be so
selective towards pterosaurs?

  It is possible the following things are likely to be true:
  1) Birds and pterosaurs of uncommon preservation may be less prone to
     being near the aquatic area into which they all have been found; that
     is, they preferred another habitat, and the catastrophies that hit
     would favor those near the lakeshore/estuarine environments Liaoning
     possesses.
  2) The catastrophes struck at particular seasons, so that if there were
     seasonal migrants, only some species would be affected at some times;
     *Confuciusornis,* by far the highest-represented amniote in Liaoning,
     followed by *Hyphalosaurus,* may be a year-round animal; animals of
     rare recovery may be faunal migrants.
  3) While the Jiufotang Formation is a study in TIME, pterosaurs and rare
     birds may not have been present EVER in some regions of the habitat,
     and their recovery indicates a allo- or sympatric association.
  4) As in (2), the rarer animals may not have been present during most of
     the catastrophic "killing" events, but rather than seasonally ...
what
     if the events occured during day-time more than not, and the rarer
     animals were nocturnal, indicating a bias towards diurnal animals in
     the sediments?

  In none of these scenarios is there suggestions of competition or
diversity declination. Selection is biased, favoring fish, insects, and
birds; then comes lizards and lizard-like animals and amphibians; then
pterosaurs and plants; and finally mammals and dinosaurs. Note that some
of these things should be present year-round, and not be involved in the
competition extremes, yet their preservation is rare (*Archaefructus* is
an example) to very rare (*Eomaia*).

  Thus I offer these _testable_ hypotheses, and offer that they can also
be extrapolated to other catastrophic events in deep time. Perhaps we
should test by applying, critically and exhaustively, these alternate
ideas before settling and doggedly advocating contrary theories?

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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