only be partially secured. In 1889, Tyrrell's colleague Thomas Chesmer Weston found an incomplete smaller skull associated with some skeletal material at a location nearby. The two skulls were assigned to the preexisting species Laelaps incrassatus by Edward Drinker Cope in 1892; although the name Laelaps was preoccupied by a genus of mite and had been changed to Dryptosaurus in 1877 by Othniel Charles Marsh, Cope refused to recognize the new name created by his archrival. However, Lawrence Lambe used the name Dryptosaurus incrassatus instead of Laelaps incrassatus when he described the remains in detail in 1903 and 1904, a combination first coined by Oliver Perry Hay in 1902. Shortly later, Osborn pointed out that D. incrassatus was based on generic tyrannosaurid teeth, so the two Horseshoe Canyon skulls could not be confidently referred to that species. The Horseshoe Canyon skulls also differed markedly from the remains of D. aquilunguis, type species of Dryptosaurus, so Osborn created the new name Albertosaurus sarcophagus for them in 1905. He did not describe the remains in any great detail, citing Lambe's complete description the year before. Both specimens (the holotype CMN 5600 and the paratype CMN 5601) are stored in the Canadian Museum of Nature in Ottawa. By the early twenty-first century, some concerns had arisen that, due to the damaged state of the holotype, Albertosaurus might be a nomen dubium that could only be used for the type specimen itself because other fossils could not reliably be assigned to it. However, in 2010, Thomas Carr established that the holotype, the paratype and comparable later finds all shared a single common unique trait or autapomorphy: the possession of an enlarged pneumatic opening in the back rim of the side of the palatine bone, proving that Albertosaurus was a valid taxon. Dry Island bone bed On 11 August 1910, American paleontologist Barnum Brown discovered the remains of a large group of Albertosaurus at another quarry alongside the Red Deer River. Because of the large number of bones and the limited time available, Brown's party did not collect every specimen, but made sure to collect remains from all of the individuals that they could identify in the bone bed. Among the bones deposited in the American Museum of Natural History collections in New York City are seven sets of right metatarsals, along with two isolated toe bones that did not match any of the metatarsals