An amateur paleontologist hunting for shark teeth in a New Jersey stream bed found something a lot more interesting: one half of an arm bone from an ancient, massive sea turtle, reports the LA Times. The astonishing part is that the other half of the bone has been sitting in a museum for 165 years, reports Phys.org. "As soon as I saw them fit together—it was just like, what I'm seeing in front of me can't be happening," says Jason Schein of the New Jersey State Museum. "It's too crazy."
The strangeness got rolling in 2012 when an amateur named Gregory Harpel found the bone and brought it to the Jersey museum. Experts there recognized it as a turtle fossil and thought it looked vaguely familiar, reports Nature. Sure enough, when they brought it to the Academy of Natural Sciences of Drexel University, it lined up perfectly with a bone that wound up in the collection there in 1849. It's striking for two scientific reasons: First, the bone makes clear that the 70-million-year-old turtle it came from was probably about 10 feet long, one of the largest ever known. Second, the 2012 discovery defies conventional wisdom about fossils—scientists can't believe the newly discovered half, despite being exposed, is generally in the same condition as the one that's been safely tucked away for more than a century.