Supplementary files of "Discovery of large eusauropod dinosaur from the earliest Middle Jurassic of China"

Sauropod dinosaurs were the largest terrestrial animals to have ever lived on Earth. However, in the initial evolutionary stages of sauropod gigantism, few fossils are known. In China, most non-sauropod sauropodomorphs from the Early Jurassic Lufeng Formation of southwestern China do not exceed 10 m in length, while all sauropods from the Middle Jurassic (Bajocian-Bathonian) Dashanpu quarry in the Sichuan Basin do exceed 10 m in length, with its largest member (Omeisaurus) around 16 t and 20 m long. Here, we report two large middle-posterior centra from dorsal vertebrae (the largest and most complete measures 142 mm in length; 201 mm in height, and 230 mm in width at its posterior articular surface) and other associated elements recovered from the earliest Middle Jurassic (Aalenican-earliest Bajocian) Xintiangou Formation in the Sichuan Basin of southwestern China. We perform a cladistic analysis and anatomical study to explore the affinities of the Xintiangou material and the early evolution of sauropod gigantism. The Xintiangou material is most likely an early-diverging eusauropod dinosaur. We recovered the specimen as being a diplodocoid sauropod belonging to the family Dicraeosauridae. This specimen was probably one of the first large-bodied sauropods in China, and may have been one of the largest in the world during the earliest Middle Jurassic. This discovery also provides further support for eusauropod-dominated assemblages that could have existed in China at the beginning of the Middle Jurassic.