Late Cretaceous – 73 – 70 Mya
Length: 9 meters (30 feet)
Height: 4.5 meters (15 feet)
Weight: 2,722 kg (6,000 lb)
In the deltas and floodplains of the Horseshoe Canyon Formation of the Western Interior Seaway, Albertosaurus was the apex predator of its time.
Perhaps as evidence of pack-hunting, 22 Albertosaurus individuals ranging from six juveniles between the ages of 2 and 11 years of age, seven sub-adults between 12 and 16, eight adults between 17 and 23 and one very old adult estimated to be 28 years of age were found in one location. It has been theorized that the juveniles and adults occupied different niches on the feeding chain and that the fleeter footed juveniles and sub-adults may have driven prey towards the slower, but more powerful, adults.