Scientists believe a new "supermassive" dinosaur species was the size of seven Tyrannosaurus Rex.
The Dreadnoughtus schrani - meaning "fearer of nothing" - is believed to be one of the largest ever land animals.
Around 70% of its remains were found in southern Patagonia, Argentina between 2005 and 2009.
The creature was 85 ft long and weighed 65 tonnes - the equivalent of seven Tyrannosaurus Rex or a dozen African elephants - when it lived some 77 million years ago.
And researchers say the creature was still growing when it died as a result of flooding.
"It is by far the best example we have of any of the most giant creatures to ever walk the planet," said lead researcher Kenneth Lacovara.
Although larger fragmentary remains of other species have been found, the Dreadnoughtus is the largest land animal for which a body mass can be estimated.
The creatures would have stood in one place every day purely eating enormous quantities of plants due to their "life-long obsession with eating".
The size of the Dreadnoughtus would have struck fear into potential predators and attacking it would "have been suicidal".