Editing Allosaurus (section)

===Species===
[[File:Skulls of Allosaurus species.png|thumb|upright|Diagram comparing skulls of three recognized species; ''A. fragilis'' (A), ''A. jimmadseni'' (B), ''A. europaeus'' (C)]]
Seven species of ''Allosaurus'' have been named: ''A. anax'',<ref name="DEA24"/> ''A. amplus'',<ref>{{cite journal | last1 = Galton | first1 = Peter M. | last2 = Carpenter | first2 = Kenneth | last3 = Dalman | first3 = Sebastian G. | year = 2015 | title = The holotype pes of the Morrison dinosaur ''Camptonotus amplus'' Marsh, 1879 (Upper Jurassic, western USA) – is it ''Camptosaurus'', Sauropoda or ''Allosaurus''? | journal = Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen | volume = 275 | issue = 3| pages = 317–335 | doi = 10.1127/njgpa/2015/0467 |doi-access=free| bibcode = 2015NJGPA.275..317G }}</ref> ''A. atrox'',<ref name=DJC00/> ''A. europaeus'',<ref name=OMetal06/> the [[type species]] ''A. fragilis'',<ref name=HMC04/> ''A. jimmadseni''<ref name=DJC20>{{cite journal |last1=Chure |first1=D.J. |last2=Loewen |first2=M.A. |year=2020 |title=Cranial anatomy of ''Allosaurus jimmadseni'', a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America |journal=PeerJ |volume=8 |page=e7803 |doi=10.7717/peerj.7803|pmid=32002317 |pmc=6984342 |doi-access=free }}</ref><ref name=DJC00/> and ''A. lucasi''.<ref>{{cite journal | last1 = Dalman | first1 = Sebastian G. | year = 2014 | title = Osteology of a large allosauroid theropod from the Upper Jurassic (Tithonian) Morrison Formation of Colorado, USA | url = https://vjs.pgi.gov.pl/article/view/26617 | journal = Volumina Jurassica | volume = 12 | issue = 2 | pages = 159–180 | doi = <!-- none --> | archive-date = November 9, 2021 | access-date = September 30, 2020 | archive-url = https://web.archive.org/web/20211109005352/https://vjs.pgi.gov.pl/article/view/26617 | url-status = live }}</ref> Among these (excluding ''A. anax'', which was named in 2024), Daniel Chure and Mark Loewen in 2020 only recognized the species ''A. fragilis'', ''A. europaeus'', and the newly-named ''A. jimmadseni'' as being valid species.<ref name=DJC20/> Some studies have suggested that ''A. europaeus'' does not show any unique characters compared to the North American species,<ref name="MDOE07"/><ref>{{Cite journal |last1=Evers |first1=Serjoscha W. |last2=Foth |first2=Christian |last3=Rauhut |first3=Oliver W.M. |date=February 7, 2020 |title=Notes on the cheek region of the Late Jurassic theropod dinosaur ''Allosaurus'' |journal=PeerJ |volume=8 |pages=e8493 |doi=10.7717/peerj.8493 |issn=2167-8359 |pmc=7008823 |pmid=32076581 |doi-access=free }}</ref><ref name=Malafaia2025/> though other authors have suggested that the species is valid and has a number of distinguishing characters.<ref name=":2">{{Cite journal |last1=Burigo |first1=André |last2=Mateus |first2=Octávio |date=January 2025 |title=''Allosaurus europaeus'' (Theropoda: Allosauroidea) Revisited and Taxonomy of the Genus |journal=Diversity |language=en |volume=17 |issue=1 |pages=29 |doi=10.3390/d17010029 |doi-access=free |issn=1424-2818}}</ref>

''A. fragilis'' is the type species and was named by Marsh in 1877.<ref name=OCM77/> It is known from the remains of at least 60 individuals, all found in the [[Kimmeridgian]]–[[Tithonian]] [[Upper Jurassic]]-age Morrison Formation of the United States, spread across [[Colorado]], [[Montana]], [[New Mexico]], [[Oklahoma]], [[South Dakota]], Utah, and Wyoming.<ref name=HMC04/> Details of the [[humerus]] (upper arm) of ''A. fragilis'' have been used as diagnostic among Morrison theropods,<ref name=JM76/> but ''A. jimmadseni'' indicates that this is no longer the case at the species level.<ref name=DJC00/>

''A. jimmadseni'' has been scientifically described based on two nearly complete skeletons. The first specimen to wear the identification was unearthed in Dinosaur National Monument in northeastern Utah, with the original "Big Al" individual subsequently recognized as belonging to the same species.<ref name=DJC20/><ref name=DJC00/><ref name=DFG03>{{cite book |last=Glut |first=Donald F. |title=Dinosaurs: The Encyclopedia. 3rd Supplement |year=2003 |publisher=McFarland & Co. |location=Jefferson, North Carolina |isbn=978-0-7864-1166-5 |pages=[https://archive.org/details/dinosaursencyclo00glut_2/page/221 221–233] |chapter=Allosaurus |chapter-url=https://archive.org/details/dinosaursencyclo00glut_2 |url=https://archive.org/details/dinosaursencyclo00glut_2/page/221 }}</ref><ref>{{Cite web|url=https://phys.org/news/2020-01-species-allosaurus-utah.html|title=New species of Allosaurus discovered in Utah|website=phys.org|access-date=January 24, 2020|archive-date=November 9, 2021|archive-url=https://web.archive.org/web/20211109005406/https://phys.org/news/2020-01-species-allosaurus-utah.html|url-status=live}}</ref> This species differs from ''A. fragilis'' in several anatomical details, including a [[jugal]] (cheekbone) with a straight lower margin. Fossils are confined to the Salt Wash Member of the Morrison Formation, with ''A. fragilis'' only found in the higher Brushy Basin Member.<ref name=LSCC03>{{cite journal |last1=Loewen |first1=Mark A. |last2=Sampson, Scott D. |last3=Carrano, Matthew T. |last4= Chure, Daniel J. |year=2003 |title=Morphology, taxonomy, and stratigraphy of ''Allosaurus'' from the Upper Jurassic Morrison Formation |journal=Journal of Vertebrate Paleontology |volume=23 |issue=3|page=72A | doi = 10.1080/02724634.2003.10010538 |s2cid=220410105 }}</ref> However, stratigraphic work done by Suzannah Maidment found that both species were actually coeval and were instead segregated by geography, with ''A. fragilis'' mostly found in the southern parts of the Morrison Formation, while ''A. jimmadseni'' is largely found in the northern parts.<ref>{{cite journal |title=Diversity through time and space in the Upper Jurassic Morrison Formation, western U.S.A. |journal=Journal of Vertebrate Paleontology |date=2023 |doi=10.1080/02724634.2024.2326027 |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2326027 |last1=Maidment |first1=Susannah C. R. |volume=43 |issue=5 |url-access=subscription }}</ref> The specific name ''jimmadseni'' is named in honor of Madsen, for his contributions to the taxonomy of the genus, notably for his 1976 work.<ref name="DJC20" />

[[File:Allosaurus anax (holotype, OMNH 1771).png|thumb|left|upright=0.9|Holotype postorbital of ''A. anax'']]
''A. fragilis'', ''A. jimmadseni'', ''A. anax'', ''A. amplus'', and ''A. lucasi'' are all known from remains discovered in the [[Kimmeridgian]]–[[Tithonian]] [[Upper Jurassic]]-age Morrison Formation of the United States, spread across [[Colorado]], [[Montana]], [[New Mexico]], [[Oklahoma]], [[South Dakota]], [[Utah]] and [[Wyoming]]. ''A. fragilis'' is regarded as the most common, known from the remains of at least 60 individuals.<ref name=HMC04/> For a while in the late 1980s and early 1990s, it was common to recognize ''A. fragilis'' as the short-snouted species, with the long-snouted taxon being ''A. atrox.''<ref name=GSP88/><ref name=LG93>{{cite book |last1=Lessem |first1=Don |last2=Glut, Donald F. |year=1993 |title=The Dinosaur Society's Dinosaur Encyclopedia |chapter=Allosaurus |pages=[https://archive.org/details/dinosaursocietys00less/page/19 19–20] |publisher=Random House |isbn=978-0-679-41770-5 |oclc=30361459 |chapter-url=https://archive.org/details/dinosaursocietys00less/page/19 }}</ref> However, subsequent analysis of specimens from the Cleveland-Lloyd Dinosaur Quarry, Como Bluff, and Dry Mesa Quarry showed that the differences seen in the Morrison Formation material could be attributed to individual variation.<ref name=DKS96/><ref name=DKS99/> A study of skull elements from the Cleveland-Lloyd site found wide variation between individuals, calling into question previous species-level distinctions based on such features as the shape of the lacrimal horns and the proposed differentiation of ''A. jimmadseni'' based on the shape of the [[jugal]].<ref name=KC2010/> ''A. anax'' was described and named in 2024 from several fossils representing various skeleton parts, the holotype being a [[postorbital]] numbered as OMNH 1771. This species is characterized by the lack of rugose ornamentation on the postorbital, the dorsal vertebrae with hourglass-shaped centra and [[Skeletal pneumaticity|pneumatic]] foramina, and other features of the postorbital, cervical vertebrae, and [[fibula]]. The specific name comes from the Ancient Greek ἄναξ (''anax'', "king", "lord" or "tribal chief"), and is intended to be an updated reference to the now [[Nomen dubium|dubious]] saurischian genus ''[[Saurophaganax]]'', to which the fossils were previously attributed.<ref name="DEA24">{{Cite journal |last1=Danison |first1=Andrew |last2=Wedel |first2=Mathew |last3=Barta |first3=Daniel |last4=Woodward |first4=Holly |last5=Flora |first5=Holley |last6=Lee |first6=Andrew |last7=Snively |first7=Eric |year=2024 |title=Chimerism in specimens referred to ''Saurophaganax maximus'' reveals a new species of ''Allosaurus'' (Dinosauria, Theropoda) |journal=Vertebrate Anatomy Morphology Palaeontology |language=en |volume=12 |doi=10.18435/vamp29404 |issn=2292-1389 |doi-access=free}}</ref>

The ''Allosaurus'' material from Portugal has a controversial taxonomic research history. The Andrés ''Allosaurus'' specimens, consisting of very complete cranial and post-cranial remains, have been attributed to ''A. fragilis'',<ref name="PMetal99"/><ref>Dantas, P., Pérez-Moreno, B., Chure, D., Silva, C. M. da, Santos, V. F., Póvoas, L., Cachão, M., Sanz, J., Pires, C., Bruno, G., Ramalheiro, G., & Galopim De Carvalho, A. M. (1999). O dinossáurio carnívoro ''Allosaurus fragilis'' no Jurássico superior português. ''Al-Madan'', ''8'', 23–28. <nowiki>https://doi.org/10.13140/RG.2.1.3224.1762</nowiki></ref><ref name="MDOE07"/> ''A.'' sp<ref name=":4"/>'', A. europaeus''<ref name="OMetal06"/> and ''A.'' cf. ''europaeus''.<ref name=":6"/> The Vale Frades ''Allosaurus'', consisting of a partial skull and cervical vertebrae and ribs, is the type specimen of ''A. europaeus'',<ref name="OMetal06"/> although the validity of that species has been previously questioned.<ref name="MDOE07"/><ref name=":3"/> In 2024, a revised diagnosis of ''A. europaeus'' was published, confirming the validity of the species.<ref name=":2"/> The specific affinities of the Andrés specimens are still unclear.

The issue of species and potential synonyms was historically complicated by the [[Type (biology)|type specimen]] of ''Allosaurus fragilis'' ([[Peabody Museum of Natural History|YPM]] 1930) being extremely fragmentary, consisting of a few incomplete vertebrae, limb fragments, rib fragments, and a single tooth. Because of this, several scientists have interpreted the type specimen as potentially dubious, meaning the genus ''Allosaurus'' itself or at least the species ''A. fragilis'' would be a ''nomen dubium'' ("dubious name", based on a specimen too incomplete to compare to other specimens or to classify). To address this situation, [[Gregory S. Paul]] and [[Kenneth Carpenter]] ([[2010 in paleontology|2010]]) submitted a petition to the [[International Commission on Zoological Nomenclature|ICZN]] to have the name ''A. fragilis'' officially transferred to the more complete specimen USNM 4734 (as a [[neotype]]),<ref name="GPKC2010">{{cite journal |last1=Paul |first1=Gregory S. |author-link1=Gregory S. Paul |last2=Carpenter |first2=Kenneth |author-link2=Kenneth Carpenter |year=2010 |title=''Allosaurus'' Marsh, 1877 (Dinosauria, Theropoda): proposed conservation of usage by designation of a neotype for its type species ''Allosaurus fragilis'' Marsh, 1877 |url=http://gspauldino.com/images/BZN67(1)Case3506.pdf |journal=Bulletin of Zoological Nomenclature |volume=67 |issue=1 |pages=53–56 |doi=10.21805/bzn.v67i1.a7 |s2cid=81735811 |archive-date=August 9, 2017 |access-date=September 28, 2018 |archive-url=https://web.archive.org/web/20170809142848/http://gspauldino.com/images/BZN67(1)Case3506.pdf |url-status=live }}</ref> a decision that was ratified by the ICZN on December 29, 2023.<ref>{{cite journal |title=Opinion 2486 (Case 3506) – Allosaurus Marsh, 1877 (Dinosauria, Theropoda): usage conserved by designation of a neotype for its type species Allosaurus fragilis Marsh, 1877 |journal=The Bulletin of Zoological Nomenclature |date=December 2023 |volume=80 |issue=1 |pages=65–68 |doi=10.21805/bzn.v80.a015 |url=https://bioone.org/journals/the-bulletin-of-zoological-nomenclature/volume-80/issue-1/bzn.v80.a015/Opinion-2486-Case-3506--Allosaurus-Marsh-1877-Dinosauria-Theropoda/10.21805/bzn.v80.a015.short |issn=0007-5167|url-access=subscription }}</ref>

Teeth of indeterminate species of ''Allosaurus'' have been reported from Tönniesberg and Kahlberg in [[Saxony]], Germany, dating to the upper Kimmeridigian.<ref name=":2"/>