A neornithischian dinosaur from the Middle Jurassic Xintiangou Formation of Yunyang, Chongqing, China: the earliest record in Asia

ABSTRACT

A new neornithischian dinosaur, Sanxiasaurus modaoxiensis gen. et sp. nov., is described based on a partial postcranial skeleton from the Middle Jurassic Xintiangou Formation of Yunyang, Chongqing Municipality, China. It is the first neornithischian dinosaur from the Middle Jurassic Xintiangou Formation of Sichuan Basin, and also the earliest record of a neornithischian dinosaur in Asia. It differs from other neornithischians in possessing the following unique combination of characters: at least four sacrals; humerus strongly bowed laterally along its length; obturator process located at mid-length of ischial shaft; lesser trochanter of femur broadened, wing shaped and subequal in anteroposterior width to greater trochanter; distal tibia with elongate posterolateral process. Phylogenetic analysis shows that Sanxiasaurus modaoxiensis is positioned near the base of neornithischia. This find extends the Asia neornithischian stratigraphic horizon to the lower Middle Jurassic.

KEYWORDS:

• Neornithischian
• Xintiangou Formation
• Middle Jurassic
• Yunyang
• Chongqing

Acknowledgments

We thank XU Xing (IVPP) for helpful discussion and offering many valuable suggestions. We thank ZHANG Yu-Qing and others for preparing the specimen, LI Qi for helping photograph of CLGPR V00003, YE Yong, JIANG Shan for providing information on Agilisaurus and Hexinlusaurus of Zigong Dinosaur Museum.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study is supported by the Project of Dinosaur Fossil Protection and Research of Chongqing Planning and Natural Resources Bureau [No. kj-2018035]; Natural Science Foundation of Chongqing, China [No. cstc2018jcyjAX0435]; Postdoctoral Project of Chongqing, China [No. Xm2017069].