Climate Changes Mid-late Dinosaur era.

[His Dark Lordship <darklord@compusmart.ab.ca>]

Alright, after reading the mail flow for the past 24 hours I feel really
outclassed, but I'll give this a shot..

What my question is is what exactly do we know (evidence wise) about the
global climate for the periods between 135 MYA and about 80 MYA (that runs
between the Jurassic and Cretacious, I think.)

The reason being is that, as I understand it, we notice a significant drop
in the Sauropod and gigantic plant eaters and a larger rise in the lower to
the ground plant eaters, such as Hadrosaurs, Anklyosaurids and others,
whilst the Carnivore side of the spectrum appears to be somewhat similiar
(although there is a shift from the classic Carnosaur to the Tyrannosaur in
the northern hemesphere.)

Now, there is evidence to suggest that several late Cretecious species (such
as the Ceratopsids) that occur in the Northern Hemesphere hold their
origins in Australia/Antartica, as well as there is evidence that suggests
that there were migrations/herds of hardrosaurs that spaned across North
America, South America, Antartica and Australia.

So, once again, what theories and hard evidence is out there about any
dramatic climatic changes that occured between 135 MYA and 80 MYA?

I have a bit of a theory in the works here but I want to decide if it's
actually plausible before I go shooting my mouth off.