- Not to be confused with Giganotosaurus.
Gigantosaurus Megalonyx (meaning "Giant or Really Large Lizard") is a genus of sauropod that lived in what is now the United Kingdom during the late jurassic period. It was the evolved form of the prosauropods that survived the triassic extinction and adapted to the jurassic forests. It developed a longer neck and longer legs for reaching high to the treetops. Gigantosaurus had a small head with smooth, flat teeth for crunching vegetation.