One of the biggest of the meat-eating dinosaurs may have hunted in packs, according to experts in Argentina.
The dinosaur is about the size of a T. rex
At least seven T. rex-sized Mapusaurus roseae have been found together in the fossil-rich Patagonia region of the country.
A pack hunting strategy might have enabled the two-legged carnivore to overpower even bigger plant-eating sauropod dinosaurs.
Details of the discoveries appear in the scientific journal Geodiversitas.
Co-author Rodolfo Coria of the Carmen Funes Museum in Plaza Huincul, Argentina, said the dig showed evidence of social behaviour in Mapusaurus.
The excavation 24km (15 miles) south of Plaza Huincul found hundreds of bones from several Mapusaurs but none from any other creature. Dr Coria said the evidence suggested the animals were together before they died.
Though it was possible they hunted in packs, there was no direct evidence for this, he added.
Philip Currie of the University of Alberta in Canada speculated that pack hunting could have allowed Mapusaurs to prey on the biggest known dinosaur, Argentinasaurus, a 37.5m-long (125ft) plant-eater.
It is not clear whether the animals cooperated in hunting, as wolves or lions do, or simply mobbed their prey or just gathered around after one of them made a kill.
Dr Currie said it was hard to say how long the biggest specimen was because no complete skeleton had been found. He estimated it might have measured about 12.3m (41ft) from the snout to the tip of the tail.