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Re: Long, long last gasp.



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

<Competition is not limited to species beating each other to the food
trough.  For barnacles it might be a relative inability to cope with
desiccation.  And, for pterosaurs, it might have been a relative
inability, relative to birds, to cope with predation.  So, absence of
large birds is not necessarily important for the competition hypothesis.>

  Competition implies two organisms outcompete one another for the same
food source or niche, or region in which to get food, where one organism
fails for a variety of reasons, but explicably due to the greater success
of the first organism. I cannot see how an animal can just survive and the
other die, to call this "competition." If one animal is hunted out, dies
by disease, or cannot fly, it is not outcompeted by one organism that
fails to die of disease, etc., as far as I can tell, in this semantic
argument.

<Yes!  If and when this is ever established, this would remove two very
important members from the body count.>

  Ah, but one of the points of my argument (the smaller one) was that
enantiornithine extinction also appears to dwindle at the end of
Cretaceous as much as pterosaurs, and that there is NO evidence that they
_could_ compete with each other, thus the idea that each's extinction
could be caused by the other is very tenuous. One could use the one to
cause the extinction of the other, but this requires that one survive, by
whatever means, and that this would not reduce the "body count" by two
groups, just one prior to the K/T; the K/T would ahve to have killed the
surviving group off, or the event took them both out, or they both took
one another out surprisingly just a million or so years prior to the
unresolved environmental dating of the extinction event[s] or
inhospitality of the world at the K/T. I have a strong gut feeling that
enants may have surpased the K/T boundary, but cannot support this, due to
latest Cretaceous diversity in faunal niches that seem to have supported
some ornithurines as well, as in the upper Maastrichtian of North America.
There was sufficient diversity to argue that ornithurines and
enantiornithines had exemplative diversity to avoid outcompetition,
despite arguments contrary to this. Animals today avoid one another, or
are prevented from avoiding one another, by either dischronal activities,
or being separated by geography: tinamous are very similar to chickens,
one could argue, and the Gondwanan diversity of large ratites seems to
"prevent" large neognath cursors, the largest known being the flighted
secretary bird, which isn't very cursorial in actuality. Roadrunners exist
in an area with no ratites, and they're not very big.

  The other, larger point: we don't know enough about the populations or
diversities to argue outcompetion in any species, and should refrain
without having excellent bonebed distributions in the upper Upper
Cretaceous with which to draw conclusions from. Sampling and
preservational biases don't give us the best picture of all, y'know.

=====
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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