Courtesy of Eric Buffetaut

A tiny conical tooth embedded in a pterosaur neck bone is all that remains of a 100-million-year-old battle between a flying reptile with a 12-foot wingspan and a 26-foot-long crocodile-snouted spinosaur. Eric Buffetaut, a paleontologist at the National Center for Scientific Research in France, was cleaning up the pterosaur’s fossilized remains when his work suddenly went forensic: He found the tooth of a creature named Irritator challengeri, a Tyrannosaurus rex cousin that was thought to eat only fish, embedded in the animal’s neck. The lifelike arrangement of Buffetaut’s find brings an ancient competition dramatically to life—the prey evidently escaped, taking one of its would-be predator’s teeth with it—and is forcing dinosaur experts to rethink the dining habits of the ancient beasts.