Temporal range: Upper Jurassic
Mamenchisaurus was a long-necked, long-tailed, four-legged, plant-eating dinosaur.
Mamenchisaurus had the longest neck of any known dinosaur, except the newly found Sauroposeidon. Mamenchisaurus' neck was about 46 feet (14 m). It had 19 vertebrae in its neck, more than any other known dinosaur had. Mamenchisaurus was about 70 to 80 feet (21 to 25 m) long and weighed roughly 12 tons (11 tonnes).