Multiple Tracksites with Parallel Trackways from the Cretaceous of the Yeosu City Area Korea: Implications for Gregarious Behavior in Ornithopod and Sauropod Dinosaurs

Abstract

At least six sites with multiple parallel ornithopod trackways and one site with three parallel sauropod trackways have been mapped in the track-rich Cretaceous sequence on Sado and Chudo islands, Yeosu City area, South Korea. A preliminary study of the stratigraphic context of these tracks indicates that they were made by gregarious subadult or adult dinosaurs that frequented lake basin settings subject to a cyclic depositional regime and periodic ash fall. Bird and theropod dinosaur tracks also occur in the sequence. Mapped sites reveal between 4 and 14 regularly spaced, ornithopod trackways suggestive of herding behavior. One site reveals an 84 m-long trackway, the longest on record for an ornithopod. Only one site reveals parallel sauropod trackways indicating three animals of equal size traveling eastwards with an inter-trackway spacing of about 2.25–2.5 m. The footprints show well preserved pes claw impressions, slightly wide gauge and large manus/pes ratios (low heteropody). The sedimentological and ichnofaunal sequences share some similarities with the famous Jindong successions 50 km to the east, but they also differ significantly in age and ichnofaunal composition.