Hudiesaurus

Hudiesaurus (meaning "butterfly lizard") is an extinct genus of mamenchisaurid sauropod dinosaur that lived in present-day China during the Late Jurassic period. It was described by Chinese paleontologist Dong Zhiming in 1997. The genus contains a single species, Hudiesaurus sinojapanorum, named based on a single vertebra. However, he also assigned teeth and limb bones from a nearby locality to H. sinojapanorum. These fossils were unearthed by the Sino-Japanese Silk Road Expedition near Qiketai in Shanshan, Xinjiang province in rock layers coming from the Kalaza Formation. This formation dates to between the Late Kimmeridgian and Tithonian stages of the Late Jurassic, 154 to 143 million years ago. Dong believed that the vertebra was a dorsal (trunk) vertebra, but later analysis suggested that it is one of the last cervical (neck) vertebrae. In 2021, the limb bones were assigned to a distinct genus of sauropod, Rhomaleopakhus, and the teeth were classified as an indeterminate eusauropod.

Hudiesaurus is one of the largest dinosaurs known, possibly reaching in length and in body mass. However, if the vertebra is a dorsal vertebra the length would be closer to and the mass around . Its vertebra is robust, large, and wide, with a width of . The (the uppermost part of a vertebra) is bifurcated (split at the top), indicating that Hudiesaurus had strong lateral control over its neck. On the sides of the (body of the vertebra) are (large cavities) which would store pneumatic air sacs.