The Cretaceous Period
During the last of the dinosaur periods, the Cretaceous, which ended 65 million years ago, the world was a very warm place. Climates and oceans were warmer than they are now. Apparently, even the high latitudes, where we would expect to find cold conditions, had relatively moderate temperatures.

Cretaceous plants included the first flowering plants (angiosperms). Relatives of oaks, horsetails, sycamores and magnolias also grew.

Paleogeographic reconstructions show that during the Cretaceous Period the breakup of Pangaea, the supercontinent composed of many of today's separate continents, continued. The tropical Tethys Sea was joined from the north by the Mowry Seaway. The seaway effectively cut North America in two from north to south. The effect of this breakup and inundating of the land was to cut off pathways by for dinosaur exchanges. Isolation of many families of dinosaurs may have reduced their chances for survival. If something catastrophic happened in a small area occupied by a group, then the entire group would have been at risk.

The important point to address with students is the relationship between space and organism. How much space is needed in a classroom for each child. How much acreage is needed to feed each child? How much land is devoted to housing each child? Would the dinosaurs have the same problems of space as humans?

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