North America in the Age of Dinosaurs

A fabulous array of dinosaurs ranged across North America during the Mesozoic era. Descendants of ancient reptiles, dinosaurs had evolved as continents shifted, climates changed, and plants blossomed into modem forms. Diverse in size, shape, and behavior, dinosaurs faced no animal challenge. Yet none survived an end-of-era cataclysm. Perhaps they perished after a gigantic asteroid flung enormous amounts of pulverized rock into the atmosphere. The global cooling and darkness that likely followed are prime suspects in the snuffing out of flying reptiles, scores of marine creatures, and the lost lords of the earth.

Great sun-warmed seas covered much of the earth during the late Cretaceous, a time of mild climates and ice-free polar regions. Densely forested with sequoia-like trees, Alaska felt winter's chill but saw little frost.

The Western Interior Seaway, almost a thousand miles wide at times, flooded one-third of North America. The modem Gulf Coast was underwater, a huge bay spread over the confluence of the Ohio and Mississippi Rivers, and an arm of the sea stretched across the Hudson Bay area to the North Atlantic.

On land, flowering plants ancestral to magnolias, roses, oaks, and walnuts spread among the conifers, ferns, and palmlike cycads that had dominated most of the Mesozoic. Geologic pressures were thrusting up many of the world's high mountain ranges, including the Rockies.

North America in the Age of Dinosaurs
National Geographic

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