Teratophoneus

Scientists have different estimates. A subadult was about 6 meters (20 ft) long and weighed around 667 kg (1,470 lb), while a full-grown adult may have reached 8.7 meters (29 ft) long and weighed up to 2.5 tonnes (2.8 short tons).1

Yes, fossils of four or five Teratophoneus found together suggest they may have been social pack-hunters. The group included animals aged 4 to 22 years old and died together in a possible flood event.1

Teratophoneus was a meat-eating predator that likely hunted large dinosaurs like the duck-billed Parasaurolophus and the horned Kosmoceratops. Its deep skull and strong bite helped it take down prey.1

Teratophoneus lived about 76.5 to 75.5 million years ago, during the Late Cretaceous period. That is millions of years before T. rex appeared.1

All Teratophoneus fossils have been found in the Kaiparowits Formation of southern Utah, USA. This area was once a warm, wet floodplain near a large inland sea.1

Nobody knows for sure. As a tyrannosaur, it was probably not a fast runner, but it could likely walk quickly and ambush its prey. No speed estimates have been published.1