Fossilised bones of six young adult dinosaurs found in the same Patagonian quarry may have belonged to the biggest creature ever to have walked the Earth.
A study of the remains suggests that Patagotitan mayorum weighed around 62 tonnes and measured more than 35 metres from nose to tail.
The titanosaur lived 100 million years ago during the Cretaceous period and was a sauropod, a huge plant-eater with a long tail and neck that stood on four legs.
Vertebrae and rib bones were among the finds recovered from the quarry in southern Argentina in 2013.
Scientists now think the fossils belonged to at least six different individuals that died in a flood plain region before being preserved in mud.
The discovery is the first indication that titanosaurs engaged in social activity.
Analysis showed that Patagotitan had a probable body mass of 62 tonnes.
It was more than 15 per cent heavier than Dreadnoughtus, the largest titanosaur from which a femur (thigh bone) and humerus (forearm bone) have been preserved.
Although some estimates have given another Patagonian titanosaur, Argentinosaurus, the title of biggest land animal ever, with a body mass of more than 80 tonnes, these have not been based on limb measurements and may be unreliable.
Vertebrae from Argentinosaurus suggest it was 10 per cent smaller than Patagotitan, said the researchers led by Dr Jose Carballido.
"The above-mentioned body mass estimates, as well as these vertebral comparisons, places Patagotitan as the largest known dinosaur species," they wrote in the journal Proceedings of the Royal Society B.
Patagotitan weighed twice as much as several large sauropods from the earlier Jurassic era, a period when giant beasts such as Giraffatitan (formerly known as brachiosaurus) and Apatosaurus strode the Earth.
Sauropods were the largest land animals that ever lived, and of this group nothing matched the titanosaurs in size.
