The phylogeny and taxonomy of the Tyrannosauridae Author Holtz, T. R. text 2001 2001-12-31 Indiana University Press Bloomington Editor Tanke D. H. Editor Carpenter K. Mesozoic Vertebrate Life 64 83 book chapter 10.5281/zenodo.3245327 9bf3a9f5-cd36-4be6-bba9-49607815bcd0 3245327 Albertosaurus sarcophagus Osborn 1905 : A taxon at present only known from the Early Maastrichtian Horseshoe Canyon Formation of Alberta. The juvenile tyrannosaurid specimen from the Horseshoe Canyon Formation referred by Russell (1970) to Daspletosaurus (a taxon otherwise unknown from the Maastrichtian) may in fact be a juvenile Albertosaurus . More recently discovered material, as yet unpublished, helps to better document the rest of the anatomy of this dinosaur. Albertosaurus is comparable to Gorgosaurus in size, and like that taxon lacks many derived features shared by Daspletosaurus and Tyrannosaurus ,