Omeisaurus junghsiensis is a Primitive Sauropod from Late Jurassic China. It was 49.2 feet (15 meters) and weighed 15-20 tonnes. It was a long-necked Sauropod, probably a close relative of Mamenchisaurus. The long neck would have been useful to reach high into trees or to cover a wide area on the ground.
It was discovered in 1939 by paleontologist Yang Zhongjian. The length of its neck, however, wasn't revealed until 1980s, when a more complete skeleton was uncovered.