A giant species of dinosaur - which weighed more than a Boeing 737 - has been discovered by scientists in Argentina.
Dubbed "Dreadnoughtus", the animal would have measured 85ft (26 metres) from nose to tail and weighed more than 60 tonnes - seven times more than a Tyrannosaurus Rex.
"With a body the size of a house, the weight of a herd of elephants, and a weaponised tail, Dreadnoughtus would have feared nothing," study co-author Kenneth Lacovara of Drexel University in Philadelphia said.
Partial skeletons of potentially larger relatives have been found - the latest discovery makes it the largest land animal for which a weight has been calculated with such a degree of accuracy.
It is believed the giant was not even fully grown when it got bogged down in a flooded plain, where it died next to a smaller companion.
The find comprised over 70% of the types of bones in the dinosaur's body - 45% of its total skeleton, although there were no skull bones.
Palaeontologists uncovered most of the vertebrae from the lizard's tail, a neck vertebra with a diameter of over 0.9 metres, ribs, toes, a claw, a section of jaw and a tooth, and nearly all the bones from its four limbs, including an upper arm bone (humerus) and a thigh bone (femur) - both over 6ft tall.The femur and humerus are key to calculating the mass of extinct four-legged animals.
"Because the Dreadnoughtus type specimen includes both these bones, its weight can be estimated with confidence," said a Drexel University statement.
"It is by far the best example we have of any of the most giant creatures to ever walk the planet," added Mr Lacovara, who discovered the skeleton in southern Patagonia in 2005 and oversaw its four-year excavation.
Speaking about the animal's diet, he added: "I imagine their day consists largely of standing in one place.
"You have this 37ft-long (11 metre) neck balanced by a 30ft-long (nine metre) tail in the back.
"Without moving your legs, you have access to a giant feeding envelope of trees and green ferns. You spend an hour or so clearing out this patch that has had thousands of calories in it, and then you take three steps over to the right and spend the next hour clearing out that patch."
Prior to Dreadnoughtus, another Patagonian giant, Elaltitan, held the title for the dinosaur with the greatest calculable weight, at 43 tonnes.
Argentinosaurus, also from Argentina, was thought to be of a comparable or even greater mass than Dreadnoughtus, and longer, at about 121ft (37 metres).
But its size is estimated from a half-dozen vertebrae in its mid-back, a shinbone and a few other fragments but no upper limb bones.