Fossil trackways show small groups of carnivorous theropods such as Allosaurus moving together. They also show that they occasionally followed herds of sauropods like Diplodocus . Whether these animals were co-operating in a hunt is much more difficult to tell.
Group hunting requires quite a high degree of co-ordination and communication.
It seems much more likely that the animals were all acting independently but trying to do the same thing - hunt. Read more about this in Hunting Down Big Al .