A new basal ornithopod dinosaur from the Upper Cretaceous of South Korea

摘要

The Seonso Conglomerate (Santonian – Campanian, Late Cretacous) of Boseong site 5 (southern coast of Korean Peninsula) has yielded well-preserved postcranial material belonging to a new taxon of ornithischian dinosaur, Koreanosaurus boseongensis nov. gen., nov. sp. This dinosaur is characterized by elongated neck vertebrae, very long and massive scapulocoracoid and humerus, proportionally short hindlimbs with a low hindlimb ratio for tibia/femur, and antero-posteriorly-elongated femoral head forming an obtuse 135° angle with the femoral shaft. Koreano-saurus displays a series of neornithischian synapomorphies. Amongst Neornithischia, most features of the postcranial skeleton suggest affinities with basal ornithopods and, amongst them, particularly with a small clade formed by three genera from the Cretaceous of Montana: Zephyro-saurus schaffi, Orodromeus makelai, and Oryctodromeus cubicularis. According to the morpho-logical, phylogenetic, sedimentological, and taphonomic data at hand, it is tentatively postulated that Koreanosaurus was a burrowing dinosaur, like Oryctodromeus.