The Grand Canyon, which today we see as a colossal desert canyon, was once a shallow, clear sea full of life. In this “window in time,” researchers found a priapulid — a marine worm — with rings of teeth on its retractable mouthpart. It sounds like science fiction, but it’s real science. And it’s exactly this contrast between the familiar (a “worm”) and the surprising (an “inside-out mouth” with circular teeth) that makes these FOSSILS so irresistible for anyone who loves stories from Earth’s deep past.