Tyrannosaurus rex and his relatives hung out and hunted in bloodthirsty gangs which included young and older members, it was claimed yesterday.
Scientists believe they have evidence that the top predator dinosaurs were highly intelligent pack animals, despite T-rex being popularly depicted as a dangerous loner.
This is a myth that has grown up because their fossil skeletons tended to be found on their own, researchers claim.
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, lived around 70 million years ago.
At least half a dozen of the animals appear to have belonged to a single social group that died together.
Lead researcher Professor Philip Currie found more possible evidence of social behaviour among them on a previous expedition in Canada.
Several of the Gobi Desert skeletons were found lying side-by-side in the same rock layers, implying that they died together.
Further research involving CT scans of skulls indicated highly developed senses for hunting, and enough brain power for co-ordinated pack behaviour.
"Tyrannosaurids, I believe, were far more complex and more dangerous than we ever could have imagined," said Prof Currie, whose research is the subject of a new documentary film, 'Dino Gangs'.