Thirty-three million years ago, give or take, a crocodile stood on a shallow riverbank in what’s now Vietnam and took a dump. Then, it stepped in its own poop, leaving imprints of its long scaly fingers stamped on the turd, which was enveloped by the soft muddy ground and eventually became a fossil. To bring this ancient scene into focus, scientists had to push a car through a muddy coalfield, pop into an enclosure at a crocodile farm, and contemplate the difference, print-wise, between a foot and a penis. The…
