Evolution Dinosaurs of the Lost Continent 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 THIS IS A PREVIEW. Buy this digital issue or subscribe to access the full article. Already a subscriber or purchased this issue? Sign In Illustration by James Gurney 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. Over the course of two field seasons this single quarry—one of many in the fossil-rich rocks of the Kaiparowits Formation—had yielded a striking array of creatures, including several dinosaurs. Most impressive was a largely complete skeleton of Gryposaurus, a massive, duck-billed plant eater approaching the size of Tyrannosaurus. The crew was now under pressure to finish excavating the remaining fossils before the helicopter came in a few days to airlift the priceless cargo to a nearby road. From there the fossils would travel by truck to the Natural History Museum of Utah in Salt Lake City, where trained volunteers would painstakingly open the jackets, remove the rock and glue the bones back together over a period of months. THIS IS A PREVIEW. Buy this digital issue or subscribe to access the full article. Already a subscriber or purchased this issue? Sign In Buy Digital Issue $7.99 Add To Cart Digital Issue + Subscription $39.99 Subscribe ADVERTISEMENT Scientific American is a trademark of Scientific American, Inc., used with permission © 2015 Scientific American, a Division of Nature America, Inc. All Rights Reserved.