A new stegosaur from the late Early Cretaceous of Zuoyun, Shanxi Province, China

Stegosaurs are a minor but iconic clade of ornithischian dinosaurs. They range from the Middle Jurassic to the Early Cretaceous, but are rare and poorly represented in the Cretaceous. Before this study, there were only four valid taxa from the Cretaceous: <i>Paranthodon</i>, <i>Wuerhosaurus homheni</i>, <i>Wuerhosaurus ordosensis</i> and <i>Mongolostegus exspectabilis</i>. Here, we describe a new stegosaur, <i>Yanbeilong ultimus</i> gen. et sp. nov. from the late Early Cretaceous Zuoyun Formation (Albian in age) of Zuoyun County, Shanxi Province, P. R. China. <i>Yanbeilong</i> represents one of the latest records of a stegosaurian taxon in the world. Compared to other stegosaurs, <i>Yanbeilong</i> has several unique characteristics in dorsal vertebrae and ilio-sacral block: it has a higher neural arch and smaller neural canal of dorsal vertebrae, and it has fewer number of fused vertebrae/sacrals and fenestrae/sacral ribs in the ilio-sacral block. Although phylogenetic analysis shows that <i>Yanbeilong</i> is recovered as the sister taxon to a clade containing <i>Stegosaurus stenops</i> and <i>Wuerhosaurus homheni</i>, it differs from these two taxa in several anatomical characters of dorsasacral vertebrae ribs, sacral ribs, caudal vertebrae and ilium.