Re: Armadillos at the K/T! (long)

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

On Wed, 3 Oct 2001, David Marjanovic wrote:

> Now I realize what your basic assumption is: that nonavian dinosaurs didn't
> make any attempt to hide their nests but always preferred battle! Right? :-)

I don't know whose law it is, but it is better to run than to fight.  But
if dinosaurs ran every time a large predator approached they would never
reproduce.  This put selection on defense, and, I believe, fueled an arms
race for increasing size.

> If so, it has been falsified with the discoveries of Egg Mountain and Egg
> Island -- islands in an alkaline lake where *Maiasaura* nested -- and of
> apparent colonial nesting in oviraptorids.

On the contrary, colonies are wonderful defensive structures--as long as
by increasing the numbers of defenders you reduce the probability of
predation.

> I should also mention the
> pterosaurs from Chile that nested in the desert (as some seabirds in the
> region do today...

Not sure what you mean here.  Flying creatures can lay their nests
remote from many "home predators".  Nesting non-avians were stuck with
similar locomotory abilities as their dinosaurian predators.

> Extremely generalizing hypotheses of that sort are generally... oops :-)

That's true, generally.  But Late Cretaceous dinosaurs were united by many
similar imperatives.  According to the data I have been able to access
(Graham Worth's data base) over 90% of late K dinos were larger than
ostriches (from memory, now).  Meaning...they found it more difficult to
hide than smaller species (a mountain is easier to find than a pebble).