Discovery of Omeisaurus (Dinosauria: Sauropoda) in the Middle Jurassic Shaximiao Formation of Yunyang, Chongqing, China

摘要: A cervical vertebra recovered from the Middle Jurassic Lower Member of the Shaximiao Formation in Town of Puan, Yunyang County, Chongqing is assigned to an species undeterminata of the sauropod dinosaur Omeisaurus based on morphological and comparative study. The centrum of this mid-cervical is much hollower than solider with extremely developed fossa/foramen complex and has a high ratio (5.05) of its anteroposterior length excluding the articular ball divided by the mean value of the posterior articular surface mediolateral width and dorsoventral height. Additional features of this cervical include central length about twice the total vertebral height, a prominent midline keel on the central ventral surface, deep and long cavities bounded by centroprezygapophyseal lamina/ intraprezygapophyseal lamina and centropostzygapophyseal lamina/intrapostzygapophyseal lamina, respectively, a coel on the dorsal half of the postzygapophyseal centrodiapophyseal fossa, long prone epipophysis extending beyond the postzygapophysis facet, anteroposteriorly length of the neural spine about half the length of the centrum, and concavities on the anterior one third lateral surface of the neural spine. Therefore, this discovery reveals new morphological information on Omeisaurus, and this Omeisaurus-bearing Puan dinosaur quarry represents the easternmost occurrence of this genus.