What Wiped Out the Dinosaurs?

Imagine the badlands of eastern Montana, a stark, heavily eroded landscape of steep-sided coulees, sandstone outcrops, and boulder-strewn washes. Vegetation is sparse, little more than sage, bunchgrass, scattered islands of scrub pine, and an occasional yucca plant. It's here, south of Fort Peck Reservoir, on a sunny spring afternoon, that you could find Jack Horner lying on his belly atop a barren hill in the Hell Creek Formation, one of the world's most famous dinosaur graveyards. The paleontologist is a big man, standing 6 feet 4 inches tall, but he might just as well be a boy again, chancing upon his first dinosaur fossil, so thoroughly absorbed is he in exploring the tiny objects only inches from his face. Horner is best known for finding large skeletons, nesting colonies, and vast bone beds where herds of dinosaurs died, and his dig here has turned up a number of outstanding specimens, ...