A 30-year-old fossil was hiding bones from a mysterious ancient sea monster

Fossils collected in Osaka more than 30 years ago have revealed a surprise hiding in plain sight: four previously unrecognized bones from a giant Cretaceous mosasaur. Among them is the first confirmed premaxilla—the frontmost bone of the upper jaw—ever identified in a Japanese mosasaur fossil. Even more intriguing, parts of the skull show unusual anatomical features that don’t match known…