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Re: Armadillos at the K/T!
Jon Bois (firstname.lastname@example.org) 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
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
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
What qualitative differences between the snakes, crocs, turtles, mammals, 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
Jaime A. Headden
Where the Wind Comes Sweeping Down the Pampas!!!!
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