New stegosaurs from the Middle Jurassic Lower Member of the Shaximiao Formation of Chongqing, China

Stegosaurs are a major clade of ornithischian dinosaurs, yet because their fragmentary fossil record, interrelationships and early evolution poorly understood. Here, we describe new stegosaur, Bashanosaurus primitivus, gen. et sp. nov., some other indeterminate stegosaur materials. We provide U-Pb detrital zircon ages for horizons bounding the holotypic quarry in Lower Member Shaximiao Formation, Yunyang, Chongqing Municipality, China, which indicate Middle Jurassic (Bajocian) age. represents earliest record stegosaurs Asia one records this world. The dorsal vertebrae, scapula, coracoid, femur, plates primitivus possess several unique characters among Stegosauria, including elevation parapophyses vertebrae on stalks at base transverse processes, flared distal end small acromial process. Among armored dinosaurs (thyreophorans), these features reminiscent basally branching taxon Scelidosaurus, indicating that possesses mosaic plesiomorphic thyreophoran derived features. Phylogenetic analysis shows is earliest-diverging along with Chungkingosaurus, from Upper consistent age taxon.