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, say scientists.
A study of the remains suggests that Patagotitan mayorum weighed around 62 tonnes and measured more than 115ft (35m) 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.
Scientists now think the fossils belonged to at least six different individuals that died in a floodplain 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 69 tons (62 metric tonnes).
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% smaller than Patagotitan, said the researchers led by Dr Jose Carballido, from the Museo Paleontologico Egidio Feruglio in Argentina.
They wrote in the journal Proceedings of the Royal Society B: “The above-mentioned body mass estimates, as well as these vertebral comparisons, places Patagotitan as the largest known dinosaur species.”
Sauropods were the largest land animals that ever lived, and of this group nothing matched the titanosaurs in size.
The scientists wrote: “Here we describe a new giant titanosaur, which not only represents the largest sauropod described so far but also one of the most complete titanosaur taxa recovered to date.
“The new taxon is represented by at least six different specimens. Based on the taphonomical, histological and ecological data available, we interpret this monospecific sauropod association as the first evidence of social behaviour among giant titanosaurs.”