Ten million years ago, before the Andes rose to their full height and a vast inland sea stretched across South America, a seven-meter crocodylian named Purussaurus neivensis held dominion over one of the most diverse predator communities the world has ever known. New research published in the Journal of Vertebrate Paleontology draws on bite marks preserved in ancient bone to argue that this two-ton reptile was not merely the largest hunter in its world, but the one that truly governed it — regulating the populations of giant sloths, armored glyptodonts, and hoofed megafauna through predation s