In fact, a 120-million-year-old bird specimen housed at China’s Shandong Tianyu Museum of Nature may be the only fossilized remains of its kind. “I noticed that it had this really weird mass of stones in its esophagus, right up against the neck bones,” said O’Connor. Credit: Sunny DrorThat this ancient bird swallowed stones wasn’t surprising on its own. To figure that out, O’Connor and colleagues reviewed their work using CT scans of fossils from birds who definitely relied on gizzard stones. After examining a wide array of bird fossils, the paleontologists surprisingly uncovered that over 800 small stones in the specimen’s throat weren’t gizzard stones.