It may have been the most cataclysmic geologic event of the last 60 million years. The narrow, 400-mile-long Isthmus of Panama, once buried below the sea, rose up and connected North and South America. This new land bridge unleashed an astonishing animal encounter as prehistoric predators and prey each unique to their worlds came face to face for the first time. An armor-plated ancestor of the armadillo. A saber-toothed marsupial. A horselike creature with three-toed feet. Evolutionary history changed forever as animals from the continents clashed. Today, scientists are on a quest to discover what happened, how and why. Which creatures survived and which were vanquished? Learn about the migration of animals north and south and their transformed evolutionary trajectories. And examine the fossils to see which animals disappeared and which ones managed to move.