Daspletosaurus torosus skeletal reconstruction.

Spread throughout several different formations and potentially represented by up to 4 species (D.torosus is only known for certain to have lived in the Oldman formation, where the type specimen was found), Daspletosaurus is North America's original robust tyrannosaur... with surprisingly long arms. In the Dinosaur Park formation, where it coexists with the seemingly more common and more cursorial Gorgosaurus, Russell (1970) suggests that this genus would have mainly fed on ceratopsians, while Gorgosaurus more often targeted hadrosaurs. In the Two Medicine formation, at least three Daspletosaurus of different ages were found together with the partially-eaten remains of hadrosaurs, in a likely example of Komodo dragon-like feeding mobs.

References:
-Osborn, Henry Fairfield (1917). "Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus". Bulletin of the American Museum of Natural History. 35 (43): 733–771. hdl:2246/1334.
-Russell, Dale A. (1970). "Tyrannosaurs from the Late Cretaceous of western Canada". National Museum of Natural Sciences Publications in Paleontology.
--Brochu, C. R. (2003). "Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull". Society of Vertebrate Paleontology Memoirs. 7: 1–138. doi:10.2307/3889334. 
-Carr, Thomas D.; Varricchio, David J.; Sedlmayr, Jayc C.; Roberts, Eric M.; Moore, Jason R. (2017). "A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system". Scientific Reports. 7: 44942. doi:10.1038/srep44942.
-Bishop PJ, Hocknull SA, Clemente CJ, Hutchinson JR, Farke AA, Barrett RS, Lloyd DG. 2018. Cancellous bone and theropod dinosaur locomotion. Part III—Inferring posture and locomotor biomechanics in extinct theropods, and its evolution on the line to birds. PeerJ 6:e5777 doi.org/10.7717/peerj.5777