A new therizinosaur from the Lower Jurassic lower Lufeng Formation of Yunnan, China

ABSTRACT

A specimen collected from the Lower Jurassic Lower Lufeng Formation of Yunnan, China, represents a new genus and species of therizinosauroid theropod. It comprises an incomplete left mandibular ramus and is here named Eshanosaurus deguchiianus. Distinctive characteristics of the new species include the presence of a round fenestra in the posterior portion of the dentary, small size of tooth denticles, and denticles almost perpendicular to the anterior and posterior edges of tooth crowns. The discovery of Eshanosaurus deguchiianus extends the record of therizinosauroids from the Early Cretaceous back to the Early Jurassic. Recent phylogenetic hypotheses placing therizinosauroids within Coelurosauria imply this is the oldest known coelurosaur, and that diversification of the group began much earlier than was previously indicated by the fossil record.