Japanese Mosasaur Fossil Reveals New Premaxilla and Possible New Species

Japanese fossils collected in Osaka more than 30 years ago have yielded four previously unrecognized bones from a giant Cretaceous mosasaur. The find includes the first confirmed premaxilla—the frontmost bone of the upper jaw—ever identified in a Japanese mosasaur specimen. Examination of the skull fragments shows unusual anatomical features that do not match any known mosasaur species, suggesting the remains may belong to a new, previously unknown species. The discovery highlights the potential for overlooked diversity in the fossil record and underscores the value of reexamining older collections.