in size. This indicated the presence of at least nine individuals in the quarry. Palaeontologist Philip J. Currie of the Royal Tyrrell Museum of Palaeontology rediscovered the bonebed in 1997 and resumed fieldwork at the site, which is now located inside Dry Island Buffalo Jump Provincial Park. Further excavation from 1997 to 2005 turned up the remains of 13 more individuals of various ages, including a diminutive two-year-old and a very old individual estimated at over in length. None of these individuals are known from complete skeletons, and most are represented by remains in both museums. Excavations continued until 2008, when the minimum number of individuals present had been established at 12, on the basis of preserved elements that occur only once in a skeleton, and at 26 if mirrored elements were counted when differing in size due to ontogeny. A total of 1,128 Albertosaurus bones had been secured, the largest concentration of large theropod fossils known from the Cretaceous. Other discoveries In 1911, Barnum Brown, during the second year of American Museum of Natural History operations in Alberta, uncovered a fragmentary partial Albertosaurus skull at the Red Deer River near Tolman Bridge, specimen AMNH 5222. William Parks described a new species in 1928, Albertosaurus arctunguis, based on a partial skeleton lacking a skull excavated by Gus Lindblad and Ralph Hornell near the Red Deer River in 1923, but this species has been considered identical to A. sarcophagus since 1970. Parks' specimen (ROM 807) is housed in the Royal Ontario Museum in Toronto. No Albertosaurus fossils were found from 1926–1972, but, there has been an increase in findings since then. Apart from the Dry Island bonebed, six more skulls and skeletons have since been discovered in Alberta and are housed in various Canadian museums: specimens RTMP 81.010.001, found in 1978 by amateur paleontologist Maurice Stefanuk; RTMP 85.098.001, found by Stefanuk on 16 June 1985; RTMP 86.64.001 (December 1985); RTMP 86.205.001 (1986); RTMP 97.058.0001 (1996); and CMN 11315. None of the skeletons were found with complete skulls. Fossils have also been reported from the American states of Montana, New Mexico, Wyoming, and Missouri, but they are doubted to be from A. sarcophagus and may not even belong to the genus Albertosaurus. Two specimens from "cf Albertosaurus ".sp" have been found in Mexico (Packard Formation and Corral de Enmedio Formation). Gorgosaurus libratus In 1913, paleontologist Charles H. Sternberg recovered another tyrannosaurid skeleton