Amazonsaurus (meaning "Amazon lizard") is a genus of diplodocoidsauropod dinosaur from the early Cretaceous Period of what is now South America. It would have been a large-bodied quadrupedal herbivore with a long neck and whiplash tail. Although more deriveddiplodocoids were some of the longest animals ever to exist, Amazonsaurus was probably not more than 12 meters (40 ft) long.