Alot of species have been assigned to the genera Tyrannosaurus, Tarbosaurus, Daspletosaurus, "Nanotyrannus", Albertosaurus, and "Gorgosaurus" . Mostly all of these are dubious names. These include two (possibly three) more Daspletosaurus species: a "stretch snouted" Daspletosaurus sp., a possible Daspletosaurus sp. metataxa (intermediate, "missing link") between Daspletosaurus and T. rex and a possible new species of Daspletosaurus found in the Horseshoe Canyon Formation of Alberta, Canadada. There is five (and if Gorgosaurus is not a part of the Albertosaurus genus it would be only three more species) species of Albertosaurus: Albertosaurus sarcophagus, Albertosaurus "megragracilis", Albertosaurus libratus? and "Albertosaurus sternbergi". Not alot is known about this species. In fact, paleontologists argue if it was a part of Allosauroidea or a Tyrannosauroidea. "Nanotyrannus" is also argued about. When first discovered it was placed (in classification) as an albertosaurine in 1946 and was called for a long time as "Gorgosaurus lancensis". Not until 1988 was it renamed Nanotyrannus lancensis. It is still argued about it's classification to this day. It's classified by some to be it's own genus or a juvenile Tyrannosaurus rex. In 1970 Canadian paleontologist Dale Russell decided it was a dwarf species of Albertosaurus (Albertosaurus lancensis). Some even believe it is a dwarf species of a Tyrannosaurus (Tyrannosaurus lancensis/Tyrannosaurus rex lancensis).