This drawing shows the possible appearance of Argentinosaurus, a dinosaur from the mid Cretaceous Period (around 95 million years ago). The Argentinosaurus was a Sauropod that lived in South America, its remains were first discovered by a man named Guillermo Heredia in Argentina. Although fossil remains of this dinosaur are rare, it is believed by scientists to have been one of the longest and heaviest of all dinosaurs.