Dale Russell
In 1913, paleontologist Charles H. Sternberg recovered another tyrannosaurid skeleton from the slightly older Dinosaur Park Formation in Alberta. Lawrence Lambe named this dinosaur "Gorgosaurus libratus" in 1914. Other specimens were later found in Alberta and the US state of Montana. Finding, largely due to a lack of good "Albertosaurus" skull material, no significant differences to separate the two taxa, Dale Russell declared the name "Gorgosaurus" a junior synonym of "Albertosaurus", which had been named first, and "G. libratus" was renamed "Albertosaurus libratus" in 1970. A species distinction was maintained because of the age difference. This addition extended the temporal range of the genus "Albertosaurus" backwards by several million years and its geographic range southwards by hundreds of kilometres.