A New Hadrosauroid Dinosaur from the Mid-Cretaceous of Liaoning, China

A new hadrosauroid dinosaur, Shuangmiaosaurus gilmorei gen. et sp. nov., is described based on a complete left maxilla with articulated premaxilla and lacrimal fragments, and a complete left dentary from the mid-Cretaceous Sunjiawan Formation of Beipiao, Liaoning, northeastern China. Cladistic analysis shows that Shuangmiaosaurus is a basal hadrosauroid, and comprises the sister taxon to Hadrosauridae. In both Shuangmiaosaurus and Hadrosauridae, the maxilla-jugal suture is butt-jointed, rather than finger-in-recess articulation as in other basal hadrosauroids. However, Shuangmiaosaurus does not possess such hadrosaurid synapomorphies as the diamond-shaped maxillary crowns with reduced primary ridges and reduced marginal denticles.