A new basal ornithopod (Dinosauria, Ornithischia) from the Late Cretaceous of Mongolia

Basal ornithopods exhibit a very low diversity in Cretaceous deposits of Asia, with only two diagnostic taxa published to date. A new basal ornithopod, Haya griva, gen. et sp. nov., is described here based on several well-preserved specimens from the Late Cretaceous Javkhlant Formation of Mongolia. Haya is diagnosed by a unique combination of characters, some of which are also present in other Asian Cretaceous basal ornithopods such as a bifid caudal ramus of the jugal and a tapering and beveled predentary. Traits, such as presence of separate maxillary fenestra, otherwise only known in Hypsilophodon, show more homoplastic distributions. Phylogenetic analysis provides weak support for grouping Haya with the Chinese Cretaceous taxa Jeholosaurus and Changchunsaurus, suggesting a greater hidden diversity of such animals in Asia. The most complete prepared specimen of Haya exhibits a sizeable gastrolith mass, representing only the second occurrence among ornithopods.