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Re: Re The biggest dinosaurs

On Fri, 22 Aug 1997, Dann Pigdon wrote:
> I think maximum sizes
> have more to do with a complex interplay of environment, climate,
> and ecology (ie. other creatures in the ecosystem). 

Yes.  This _must_ be true.  And yet the taxon we call non avian dinosaurs
was bigger than any other taxon.  All other taxons faced the variables you
mention.  If dinosaurs defended their nest and were not limited in size
(unlike snakes and birds), they had a unique variable.  There may be
others, though.  I'm just saying this one is the most obvious.

> I doubt that
> any single factor contributed to the decreased size of modern mammals,

Except that, even at moderately big size (wildebeest-size) they did not
have to defend a fixed-site nest.  Growing pathologically large was of no
advantage to them.  

> and similarly that no single factor was responsible for the
> large size (or extinction for that matter) of dinosaurs.

I agree with this.  I say, though that the imperatives of nest defence may
have been responsible for the margin of difference.
I also agree with your extinction comment.  But, while extinctions _per
se_ require many influences, the different patterns of extinctions need
specific explanations.