Re: Armadillos at the K/T!

[John Bois <jbois@umd5.umd.edu>]

On Tue, 2 Oct 2001, Jaime A. Headden wrote:

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

>    The effect of birds today is irrelevant for the most part. It is
clea r that from the diversity
> of  end-Cretacous birds and dinosaurs from NA, that large terrestrial
birds  are largely unknown.

But ratites are excellent analogues for non-avian dinosaurs.  If animals
can eat their offspring, despite being completely overpowered, then
similarly-sized animals may have had similar effects in earlier times. In
other words, extant species demonstrate that predators may be vastly
smaller than prey adults.

> One bird from Europe does not affect the global nestling or egg
numbers, and cannot be used to
> affect the golbal extinction scenario.

I'm sure no one believes there was only one bird.  While this is the only
evidence, a much more likely scenario is that birds occupied a wide
variety of niches.  Also, they _must_ be considered the leading culprits
in pterosaur extinction.  Who else but birds could reach them where it
hurts--on their nesting grounds.  This would seem a source of mortality
which would blight all pterosaurs.  I can think of lots of other causes
for individual ptrosaurs, but none for all.  So, if birds impacted
pterosaur populations, they may have done the same to dinosaur
populations. 

> The value of larger animals is actually smaller
than tha t of a smaller
> animals , for in the Hell Creek and the various western [and one
eastern] E uropean levels and in
> India, th ere are more numerous smaller theropods than there are larger
ones. 

Please correct me, but I think I only have to knock off herbivores--I
claim the same dispensation as the bolide hypothesis.

> You  might want to pick up _the Dinosauria_, _the Complete
Dinosaur_, etc. an d perform
> an inventory of y our own.

What? And get some real data?  

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

I'm not sure I understand the question.  Are you asking what diferences in
predatory ability could there be between say, birds and placentals
vs. snakes and turtles?