Re: Armadillos at the K/T!

["Jaime A. Headden" <qilongia@yahoo.com>]

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

<Birds are today fearsome predators of eggs and hatchlings of ratites.  An 
earth bound predator
may fear a parent; a bird can nail a hatchling and fly off without penalty.  
This is such a threat
to rhea that they strike at airplanes flying thousands of feet in the air.>

  The effect of birds today is irrelevant for the most part. It is clear that 
from the diversity
of end-Cretacous birds and dinosaurs from NA, that large terrestrial birds are 
largely unknown.
One bird from Europe does not affect the global nestling or egg numbers, and 
cannot be used to
affect the golbal extinction scenario.

<I am under the impression that the mean size of dinosaur fossils increases 
toward their
extinction--do you have a reference as to the distribution of fossil sizes 
(adult) as related to
the progression of the Cretaceous?>

  This is largely affected by the mean loss in value of dinosaur species in the 
end of the
Cretaceous, even globally, as to compare to a mid-K (Apt-Alb, Cloverly etc.) 
and e-K (Wealden and
equivalents) fauna. The value of larger animals is actually smaller than that 
of a smaller
animals, for in the Hell Creek and the various western [and one eastern] 
European levels and in
India, there are more numerous smaller theropods than there are larger ones. As 
for papers, this
is acheived easily by picking up general works on the Hell Creek (no one paper 
will satisfy, as
there are none [to my knowledge]), Deccan India, Romania, the southern French 
and northern Spanish
localities. You might want to pick up _the Dinosauria_, _the Complete 
Dinosaur_, etc. and perform
an inventory of your own.

<But they were qualitatively different--at least this is the hypothesis.  If 
you grant that
predatory guilds today have a limiting effect on non-concealed nests, this must 
have become true
_at some time_.  If this is true, then your above argument doesn't hold.  I 
mean, there were
always small non-dinosaurean egg eaters around--but, at some point they became 
more effective.>

  What qualitative differences between the snakes, crocs, turtles, mammals, and 
birds and
dinosaurs, at the end of the Cretaceous globally are there that you note that 
make it appear that
there was a primary effect on pupulation densities brought about by egg- and 
nestling-predation?


=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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