Editing Albertosaurus (section)

==History of discovery==

===Naming===
[[File:Tyrrell - Crane Albertosaure.jpg|thumb|left|[[Holotype specimen]] CMN 5600]]
''Albertosaurus'' was named by [[Henry Fairfield Osborn]] in a one-page note at the end of his 1905 description of ''Tyrannosaurus rex''.<ref>{{Cite journal |last=Osborn |first=H.F. |date=December 31, 1905 |title=Tyrannosaurus and other Cretaceous carnivorous dinosaurs |url=https://zenodo.org/record/1038222 |journal=Bulletin of the American Museum of Natural History |volume=21 |pages=259–265 |doi=10.5281/zenodo.1038222 |archive-date=March 23, 2023 |access-date=March 23, 2023 |archive-url=https://web.archive.org/web/20230323011156/https://zenodo.org/record/1038222 |url-status=live }}</ref> Its namesake is [[Alberta]], the [[Canadian province]] established the very same year where the first remains were found. The generic name also incorporates the [[Ancient Greek|Greek]] word {{lang|grc|σαυρος}}/''sauros'', meaning "lizard", which is the most common suffix in dinosaur names. The [[type species]] is ''Albertosaurus sarcophagus'' and the [[specific name (zoology)|specific name]] is derived from the Ancient Greek term σαρκοφάγος (''{{lang|grc-Latn|sarkophagos}}''), meaning "flesh-eating", and having the same [[etymology]] as the [[sarcophagus|funeral container]] with which it shares its name, which is a combination of the Greek words σαρξ/''{{lang|grc-Latn|sarx}}'' ("flesh") and {{lang|grc|φαγειν}}/''{{lang|grc-Latn|phagein}}'' ("to eat").<ref name="osborn1905">{{cite journal |last=Osborn |first=Henry F. |author-link=Henry Fairfield Osborn |year=1905 |title=''Tyrannosaurus'' and other Cretaceous carnivorous dinosaurs |url=https://digitallibrary.amnh.org/bitstream/handle/2246/1464//v2/dspace/ingest/pdfSource/bul/B021a14.pdf?sequence=1&isAllowed=y |journal=Bulletin of the American Museum of Natural History |volume=21 |issue=3 |pages=259–265 |doi=10.1111/j.1468-5965.2007.00735_17.x |hdl=2246/1464 |archive-date=November 2, 2022 |access-date=January 1, 2023 |archive-url=https://web.archive.org/web/20221102135822/https://digitallibrary.amnh.org/bitstream/handle/2246/1464/v2/dspace/ingest/pdfSource/bul/B021a14.pdf?sequence=1&isAllowed=y |url-status=live }}</ref> More than 30 specimens of all ages are known to science.<ref name=ericksonetal2006/><ref name=currie2003b/>

===Early discoveries===
[[Image:red deer river.jpg|thumb|The [[Red Deer River]] near [[Drumheller]], [[Alberta]]. Almost three-quarters of all ''Albertosaurus'' remains have been discovered alongside the river, in outcrops like the ones on either side of this picture.]]
The [[type specimen]] is a partial skull collected on June 9, 1884, from an [[outcrop]] of the [[Horseshoe Canyon Formation]] alongside the [[Red Deer River]] in Alberta. It was recovered by an expedition of the [[Geological Survey of Canada]], led by the famous [[geologist]] [[Joseph Tyrrell|Joseph Burr Tyrrell]]. Due to a lack of specialised equipment, the almost complete skull could 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.<ref name=TankeCurrie2010>{{cite journal | last1 = Tanke | first1 = Darren H. | last2 = Currie | first2 = Philip J. | year = 2010 | title = A history of ''Albertosaurus'' discoveries in Alberta, Canada | journal = Canadian Journal of Earth Sciences | volume = 47 | issue = 9| pages = 1197–1211 | doi = 10.1139/e10-057 | bibcode = 2010CaJES..47.1197T }}</ref> The two skulls were assigned to the preexisting species ''Laelaps incrassatus'' by [[Edward Drinker Cope]] in 1892.<ref name=cope1892>{{cite journal |last=Cope |first=Edward D. |author-link=Edward Drinker Cope |year=1892 |title=On the skull of the dinosaurian ''Laelaps incrassatus'' Cope |journal=Proceedings of the American Philosophical Society |volume=30 |pages=240–245}}</ref> Although the name ''Laelaps'' was [[International Code of Zoological Nomenclature|preoccupied]] by a genus of [[mite]] and had been changed to ''[[Dryptosaurus]]'' in 1877 by [[Othniel Charles Marsh]], Cope stubbornly 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,<ref>{{cite journal | last1 = Lambe | first1 = L.M. | year = 1903 | title = On the lower jaw of ''Dryptosaurus incrassatus'' (Cope) | journal = Ottawa Naturalist | volume = 17 | page = 134 }}</ref><ref name=lambe1904>{{cite journal |last=Lambe |first=Lawrence M. |author-link=Lawrence Lambe |year=1904 |title=On ''Dryptosaurus incrassatus'' (Cope) from the Edmonton Series of the Northwest Territory |journal=Contributions to Canadian Palaeontology |volume=3 |pages=1–27|url=https://archive.org/details/LambeL.M.1904.OnDryptosaurusIncrassatuscopeFromTheEdmonton |access-date=August 29, 2010}}</ref> which was a combination first coined by [[Oliver Perry Hay]] in 1902.<ref>Hay, Oliver Perry'', 1902 Bibliography and Catalogue of the Fossil Vertebrata of North America''. Bulletin of the United States Geological Survey, N° 117, Government Printing Office. pp 868</ref>

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 gave them the new name ''Albertosaurus sarcophagus'' in 1905. He did not describe the remains in any great detail, citing Lambe's complete description the year before.<ref name=osborn1905/> 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 (paleontologist)|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]] proves that ''Albertosaurus'' is a valid [[taxon]].<ref>{{cite journal | last1 = Carr | first1 = Thomas D. | year = 2010 | title = A taxonomic assessment of the type series of ''Albertosaurus sarcophagus'' and the identity of Tyrannosauridae (Dinosauria, Coelurosauria) in the ''Albertosaurus'' bonebed from the Horseshoe Canyon Formation (Campanian–Maastrichtian, Late Cretaceous) | journal = Canadian Journal of Earth Sciences | volume = 47 | issue = 9| pages = 1213–1226 | doi = 10.1139/e10-035 | bibcode = 2010CaJES..47.1213C |url=https://www.researchgate.net/publication/233603205 }}</ref>

===Dry Island bone bed===
[[File:Albertosaurus teeth - Royal Tyrrell Museum.jpg|thumb|upright|Teeth from Dry Island and Drumheller, [[Royal Tyrrell Museum]]]] 
On August 11, 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 [[metatarsal]]s, along with two isolated toe bones that did not match any of the metatarsals 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]].<ref name=currie1998>{{cite journal|last=Currie |first=Philip J. |author-link=Philip J. Currie |year=1998 |title=Possible evidence of gregarious behaviour in tyrannosaurids |journal=Gaia |volume=15 |pages=271–277 |url=http://www.mnhn.ul.pt/geologia/gaia/21.pdf |access-date=May 3, 2009 |archive-url=https://web.archive.org/web/20090326062833/http://www.mnhn.ul.pt/geologia/gaia/21.pdf |archive-date=March 26, 2009 |url-status=dead }} (not printed until 2000)</ref> 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 {{convert|10|m|ft|abbr=off}} long. None of these individuals are known from complete skeletons and most are represented by remains in both museums.<ref name=ericksonetal2006/><ref name=ericksonetal2004/> 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, which is the largest concentration of large theropod fossils known from the Cretaceous.<ref>{{cite journal | last1 = Eberth | first1 = David A. | last2 = Currie | first2 = Philip J. | year = 2010 | title = Stratigraphy, sedimentology, and taphonomy of the ''Albertosaurus'' bonebed (upper Horseshoe Canyon Formation; Maastrichtian), southern Alberta, Canada | journal = Canadian Journal of Earth Sciences | volume = 47 | issue = 9| pages = 1119–1143 | doi = 10.1139/e10-045 | bibcode = 2010CaJES..47.1119E }}</ref>

===Other discoveries===
[[File:Albertosaurus skull Royal Tyrrell 1.jpg|thumb|left|Skull TMP 1985 098 0001]]
In 1911, Barnum Brown, during the second year of the American Museum of Natural History's operations in Alberta, uncovered a fragmentary partial ''Albertosaurus'' skull at the Red Deer River near Tolman Bridge (specimen AMNH 5222).<ref>Carpenter, K., 1992, "Tyrannosaurids (Dinosauria) of Asia and North America", In: N. Mateer and P.-J. Chen (eds.) ''Aspects of nonmarine Cretaceous geology''. China Ocean Press, Beijing, China, pp. 250–268</ref>

[[William Parks (paleontologist)|William Parks]] described a new species in 1928, ''Albertosaurus arctunguis'', based on a partial skeleton lacking a skull that was excavated by Gus Lindblad and Ralph Hornell near the Red Deer River in 1923,<ref name=parks1928>{{cite journal |last=Parks |first=William A. |author-link=William Parks (paleontologist)|year=1928 |title=''Albertosaurus arctunguis'', a new species of therapodous dinosaur from the Edmonton Formation of Alberta |journal=University of Toronto Studies, Geological Series |volume=25 |pages=1–42}}</ref> but this species has been considered identical to ''A. sarcophagus'' since 1970.<ref name=russell1970/> Parks' specimen (ROM 807) is housed in the [[Royal Ontario Museum]] in [[Toronto]].<ref name=TankeCurrie2010/>

No ''Albertosaurus'' fossils were found from 1926 to 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. Specimen RTMP 81.010.001 was found in 1978 by amateur paleontologist Maurice Stefanuk. RTMP 85.098.001 was found by Stefanuk on June 16, 1985. RTMP 86.64.001 was found in December 1985. RTMP 86.205.001 was found in 1986. RTMP 97.058.0001 was found in 1996 and then there is CMN 11315. Unfortunately, none of these skeletons were found with complete skulls.<ref name=TankeCurrie2010/> 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''.<ref name=holtz2004/><ref name=currie2003b/>

Two specimens from "cf ''Albertosaurus'' ".sp" have been found in [[Mexico]] ([[Packard Formation]] and [[Corral de Enmedio Formation]]).<ref name="sullivanlucas-alberto">Listed as "cf. ''Albertosaurus'' sp." "Corral De Enmedio and Packard Formations, Cabollona Group, Sonora, Mexico," in Sullivan and Lucas (2006). Page 16.</ref>

===''Gorgosaurus libratus''===
[[File:Albertosaurus Royal Tyrrell 2.jpg|thumb|''[[Gorgosaurus]]'', which was described as a second species of ''Albertosaurus'', ''A. libratus'' by Dale Russell.]]
In 1913, [[paleontologist]] [[Charles Hazelius Sternberg|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.<ref name=lambe1914>{{cite journal |last=Lambe |first=Lawrence M. |author-link=Lawrence Lambe |year=1914 |title=On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of the skull of ''Stephanosaurus marginatus'' from the same horizon |journal=Ottawa Naturalist |volume=28 |pages=13–20}}</ref> Other specimens were later found in Alberta and the US state of [[Montana]]. Finding no significant differences to separate the two taxa (due mostly to a lack of good ''Albertosaurus'' skull material), [[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. The addition extended the temporal range of the genus ''Albertosaurus'' earlier by several million years and its geographic range southwards by hundreds of kilometres.<ref name=russell1970/>

In 2003, [[Philip J. Currie]], benefiting from much more extensive finds and a general increase in anatomical knowledge of theropods, compared several tyrannosaurid skulls and came to the conclusion that the two species are more distinct than previously thought. As the two species are [[sister taxa]], they are more closely related to each other than to any other species of tyrannosaurid. Recognizing this, Currie nevertheless recommended that ''Albertosaurus'' and ''Gorgosaurus'' be kept as separate genera, as he concluded that they were no more similar than ''Daspletosaurus'' and ''Tyrannosaurus'', which are almost always separated. In addition to this, several albertosaurine specimens have been recovered from [[Alaska]] and [[New Mexico]]. Currie suggested that the ''Albertosaurus''-''Gorgosaurus'' situation may be clarified once these are fully described.<ref name=currie2003b/> Most authors have followed Currie's recommendation,<ref name=holtz2004/><ref name=ericksonetal2004/><ref name=ricklefs2007>{{cite journal |last=Ricklefs |first=Robert E. |year=2007 |title=Tyrannosaur ageing |journal=Biology Letters |volume=3 |issue=2 |pages=214–217 |doi=10.1098/rsbl.2006.0597 |pmid=17284406 |pmc=2375931}}</ref> but some have not.<ref name=carretal2005/>

===Other species===
In 1930, Anatoly Nikolaevich Riabinin named ''Albertosaurus pericolosus'' based on a tooth from China that probably belonged to ''[[Tarbosaurus]]''.<ref>{{cite journal | last1 = Riabinin | first1 = A.N. | year = 1930 | title = [In Russian] "On the age and fauna of the dinosaur beds on the Amur River | journal = Memoirs of the Russian Mineralogical Society | volume = 59 | issue = 2| pages = 41–51 }}</ref> In 1932, [[Friedrich von Huene]] renamed ''Dryptosaurus incrassatus'', not considered a ''nomen dubium'' by him, to ''Albertosaurus incrassatus''.<ref>Von Huene, F.'', 1932 Die fossile Reptil-Ordnung Saurischia: ihre Entwicklung und Geschichte''. Monographie für Geologie und Palaeontologie, Parts I and II, ser. I, 4: 1–361</ref> Because he had identified ''Gorgosaurus'' with ''Albertosaurus'', in 1970, Russell also renamed ''Gorgosaurus sternbergi'' (Matthew & Brown 1922) into ''Albertosaurus sternbergi'' and ''Gorgosaurus lancensis'' (Gilmore 1946) into ''Albertosaurus lancensis''.<ref name=russell1970/> The former species is today seen as a juvenile form of ''Gorgosaurus libratus'' and the latter is seen as either identical to ''[[Tyrannosaurus]]'' or representing a separate genus, ''[[Nanotyrannus]]''. In 1988, [[Gregory S. Paul]] based ''Albertosaurus megagracilis'' on a small tyrannosaurid skeleton, specimen LACM 28345, from the [[Hell Creek Formation]] of Montana.<ref name=paul1988>{{cite book |last=Paul |first=Gregory S. |author-link=Gregory S. Paul |year=1988 |title=Predatory Dinosaurs of the World |publisher=Simon & Schuster |location=New York |isbn=978-0-671-61946-6 |url-access=registration |url=https://archive.org/details/predatorydinosau00paul }}</ref> It was renamed ''[[Dinotyrannus]]'' in 1995,<ref name=olshevsky1995>{{cite journal |last=Olshevsky |first=George. |author-link=George Olshevsky |year=1995 |title=(The origin and evolution of the tyrannosaurids.) |journal=Kyoryugaku Saizensen (Dino Frontline) |volume=9 |pages=92–119 |language=ja}}</ref> but is now thought to represent a juvenile ''Tyrannosaurus rex''.<ref name=currie2003a/> Also in 1988, Paul renamed ''[[Alectrosaurus]] olseni'' (Gilmore 1933) into ''Albertosaurus olseni'',<ref name=paul1988/> but this has found no general acceptance. In 1989, ''Gorgosaurus novojilovi'' (Maleev 1955) was renamed by Bryn Mader and Robert Bradley as ''Albertosaurus novojilovi''.<ref>{{cite journal | last1 = Mader | first1 = B. | last2 = Bradley | first2 = R. | year = 1989 | title = A redescription and revised diagnosis of the syntypes of the Mongolian tyrannosaur ''Alectrosaurus olseni'' | journal = Journal of Vertebrate Paleontology | volume = 9 | issue = 1| pages = 41–55 | doi=10.1080/02724634.1989.10011737| bibcode = 1989JVPal...9...41M }}</ref>

On two occasions, species based on valid ''Albertosaurus'' material were reassigned to a different genus, ''[[Deinodon]]''. In 1922, [[William Diller Matthew]] renamed ''A. sarcophagus'' into ''Deinodon sarcophagus''.<ref>{{cite journal | last1 = Matthew | first1 = W.D. | last2 = Brown | first2 = B. | year = 1922 | title = The family Deinodontidae, with notice of a new genus from the Cretaceous of Alberta | journal = Bulletin of the American Museum of Natural History | volume = 46 | issue = 6| pages = 367–385 }}</ref> In 1939, German paleontologist [[Oskar Kuhn]] renamed ''A. arctunguis'' into ''Deinodon arctunguis''.<ref>Kuhn, O.'', 1939 Saurischia — Fossilium catalogus I, Animalia, Pars 87''. 's-Gravenhage, W. Junk, 1939, 124 pp</ref>