"Pack-hunting is a possibility, but I don't know if there's much evidence for it."
I agree that T-Rex probably was both a predator and a scavenger. As far as pack-hunting, what were the majority of potential prey animals in North America when T-Rex lived? There were thousands and thousands of Hadrasaurs, which migrated from North Western Canada south into the US, and back again.
>>There were thousands and thousands of Hadrasaurs<<
Yeah, except that's not what they were called back then.