Dinosaurs of the Lost Continent (preview)

Feature Articles | Evolution See Inside

The American West once harbored multiple communities of dinosaurs simultaneously?a revelation that has scientists scrambling to understand how the land could have supported so many behemoths

By Scott D. Sampson ?| February 29, 2012

DINING OUT: A herd of Kosmoceratops dinosaurs grazes among the cypress trees 76 million years ago in a primeval swamp in what is now southern Utah. Image: Illustration by James Gurney

In Brief

• Between 90 million and 70 million years ago, during the Late Cretaceous period, a shallow sea flooded the central region of North America, subdividing the continent into eastern and western landmasses. Scientists refer to the western landmass as Laramidia.
• In the 1980s a researcher proposed that distinct dinosaur communities inhabited the northern and southern regions of Laramidia for several million years. Critics doubted that so many large animals could have shared this relatively small chunk of land, however.
• But over the past decade discoveries in southern Utah have bolstered the notion of distinct dinosaur communities in the north and south, revealing a host of species new to science?including many giant varieties.
• Exactly what enabled so many behemoths to coexist in such a small area remains unclear, but it may be that dinosaurs had lower energy requirements than today?s large terrestrial animals do or that plants during the Late Cretaceous provided more food than their modern-day counterparts.

On a cool September morning in 2010 my crew and I began our daily descent from camp back into deep time, walking single file down a steep, knife-edge ridge of sandstone and mudstone in southern Utah?s Grand Staircase-Escalante National Monument. Each of us carried water, a field notebook, lunch, a rock hammer and other hand tools. Heavier tools and materials?rock saws, picks, shovels, bags of plaster and swaths of burlap?awaited us half a mile away at the dig site. Even from the hilltop we could easily see the plaster jackets down in the quarry?alabaster beacons in a wilderness of arid, gray-striped badlands. Some of the irregular lumps were not much bigger than a loaf of bread. Others spanned 10 feet and tipped the scales at more than a ton. All contained the bony remains of animals that coexisted here 76 million years ago.

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