Mamenchisaurus is a genus of sauropod dinosaur known for their remarkably long necks which made up nearly half the total body length. Their shoulders were somewhat higher than the hips. The different species vary in length, from around 15 m to at least 26 m, and maybe up to 35 m. The species differ in overall size and specific features of the skull and skeleton, but share typical sauropod traits, like quadrupedalism, large bodies, small heads, and long tails.