 The Dry Island bonebed discovered by Barnum Brown and his crew contains the remains of 22 Albertosaurus , the most individuals found in one locality of any Cretaceous theropod , and the second @-@ most of any large theropod dinosaur behind the Allosaurus assemblage at the Cleveland Lloyd Dinosaur Quarry in Utah . The group seems to be composed of one very old adult ; eight adults between 17 and 23 years old ; seven sub @-@ adults undergoing their rapid growth phases at between 12 and 16 years old ; and six juveniles between the ages of 2 and 11 years , who had not yet reached the growth phase . The near @-@ absence of herbivore remains and the similar state of preservation between the many individuals at the Albertosaurus bonebed quarry led Phil Currie to conclude that the locality was not a predator trap like the La Brea Tar Pits in California , and that all of the preserved animals died at the same time . Currie claims this as evidence of pack behavior . Other scientists are skeptical , observing that the animals may have been driven together by drought , flood or for other reasons . 
