Scientists believe they have evidence that the top predator dinosaurs were highly intelligent pack animals, despite T-rex being popularly depicted as a dangerous but dim-witted loner.
This is a myth that has grown up because for many years their fossil skeletons tended to be found on their own, researchers say.
The new theory follows an analysis of skeletons of the tyrannosaur Tarbosaurus bataar from 90 sites in the Gobi Desert, Mongolia.
Tarbosaurus, a cousin of T-rex that lived around 70 million years ago, was a two-legged predator up to 12 metres long and weighing five tonnes.
At least half a dozen of the animals appear to have belonged to a single social group, including adults and juveniles, that died together.