A Late Cretaceous Lakeshore
On the rocky coastlines of several islands near Yeosu, layers of sedimentary rock preserve a detailed snapshot of life during the Late Cretaceous period. Potassium-Argon dating of volcanic ash layers interspersed with the sediment confirms the tracks are between 81 and 65 million years old. This timing places them in the Campanian and Maastrichtian stages, making them some of the final records of dinosaurs in Asia before the mass extinction event. The environment at the time was a semi-arid area surrounding a large, persistent lake.
Across the islands of Sado, Chudo, Nangdo, and others, paleontologists have identified 3,546 individual dinosaur footprints. The tracks belong to three main groups. Bipedal, herbivorous ornithopods left the vast majority of the prints, accounting for 81% of the total. Most of these tracks are consistent with the ichnogenus Caririchnium. The site also contains tracks from carnivorous theropods and a few from large, four-legged sauropods. The scarcity of sauropod tracks here matches a wider pattern of their declining diversity in the Late Cretaceous.