 = Species of Allosaurus = 
 
 There have been a number of potential species assigned to the <unk> dinosaur genus Allosaurus since its description in 1877 by Othniel Charles Marsh , but only a handful are still regarded as valid . Allosaurus was originally described from material from the Upper Jurassic Morrison Formation of the western United States of America ; the type species A. fragilis became one of the best @-@ known species of dinosaur . 
 The genus Allosaurus was part of the Marsh / Cope " Bone Wars " of the late 19th century , and its taxonomy became increasingly confused due to the competition , with several genera and species named by Cope and Marsh now regarded as synonyms of Allosaurus or A. fragilis . Since the description of Allosaurus , scientists have proposed additional species from such far @-@ flung <unk> as Portugal , Siberia , and Tanzania . 
 
 = = <unk> about type specimen = = 
 
 The issue of synonyms is complicated by the type specimen of Allosaurus fragillis ( catalogue number YPM 1930 ) being extremely fragmentary , consisting of a few incomplete vertebrae , limb bone fragments , rib fragments , and a tooth . Because of this , several scientists have noted that the type specimen , and thus the genus Allosaurus itself or at least the species A. fragillis , is technically a nomen dubium ( " dubious name " , based on a specimen too incomplete to compare to other specimens or to classify ) . In an attempt to fix this situation , Gregory S. Paul and Kenneth Carpenter ( 2010 ) submitted a petition to the <unk> to have the name A. fragillis officially transferred to the more complete specimen <unk> ( as a <unk> ) . This request is currently pending review . 
 
 = = <unk> valid species = = 
 
 It is unclear how many species of Allosaurus there were . Eight species have been considered potentially valid since 1988 ( A. amplexus , A. atrox , A. europaeus , the type species A. fragilis , the as @-@ yet not formally described " A. jimmadseni " , A. <unk> , A. maximus , and A. tendagurensis ) , although only about half are usually considered valid at any given time . There are also at least ten dubious or undescribed species that have been assigned to Allosaurus over the years , along with the species belonging to genera now sunk into Allosaurus . In the most recent review of basal tetanuran theropods , only A. fragilis ( including A. amplexus and A. atrox ) , " A. jimmadseni " ( as an unnamed species ) , and A. tendagurensis were accepted as potentially valid species , with A. europaeus not yet proposed and A. maximus assigned to Saurophaganax . 
 A. fragilis is the type species and was named by Marsh in 1877 . It is known from the remains of at least sixty individuals , all found in the Kimmeridgian – Tithonian Upper Jurassic @-@ age Morrison Formation of the United States , spread across the states of Colorado , Montana , New Mexico , Oklahoma , South Dakota , Utah , and Wyoming . Details of the humerus ( upper arm ) of A. fragilis have been used as diagnostic among Morrison theropods , but the discovery of " A. jimmadseni " indicates that this will no longer be the case at the species level . 
 A. amplexus was named by Gregory S. Paul for giant Morrison allosaur remains , and included in his conception <unk> maximus ( later Saurophaganax ) . A. amplexus was originally coined by Cope in 1878 as the type species of his new genus <unk> , and is based on what is now AMNH <unk> , parts of three vertebrae , a coracoid , and a <unk> . Following Paul 's work , this species has been accepted as a synonym of A. fragilis . 
 Allosaurus material from Portugal was first reported in 1999 on the basis of <unk> / <unk> , a partial skeleton including a <unk> , vertebrae , ribs , <unk> , chevrons , part of the <unk> , and hindlimbs . This specimen was assigned to A. fragilis , but the subsequent discovery of a partial skull and neck ( ML 415 ) near <unk> , in the Kimmeridgian @-@ age Porto Novo Member of the <unk> Formation , spurred the naming of the new species A. europaeus . It differs from other species of Allosaurus in cranial details . However , more material may show it to be A. fragilis , as originally described . 
 Daniel Chure 's work on Morrison <unk> remains has been responsible , directly or indirectly , for " A. jimmadseni " and A. maximus . " A. jimmadseni " is the proposed name for a new species of Morrison allosaur , based on a nearly complete skeleton and skull . A. sp . 2 , as it is also known , differs from A. fragilis in several anatomical details including a jugal or <unk> with a straight lower margin , and is also found only in the Salt <unk> Member of the Morrison Formation , with A. fragilis only present in the higher <unk> Basin Member . A. maximus was coined by David K. Smith for Chure 's Saurophaganax maximus , a taxon created by Chure in 1995 for giant <unk> remains from the Morrison of Oklahoma . These remains had been known as <unk> , but that name was already in use , leading Chure to propose a substitute . Smith , in his 1998 analysis of variation , concluded that S. maximus was not different enough from Allosaurus to be a separate genus , but did warrant its own species , A. maximus . This <unk> was rejected in the most recent review of basal <unk> . 
 
 = = Biological variation , A. atrox , and A. fragilis = = 
 
 The perception that there were two common Allosaurus species in the Morrison Formation was popularized in Gregory S. Paul 's 1988 book Predatory Dinosaurs of the World . Paul proposed that A. fragilis had tall pointed horns and a slender build compared to a postulated second species A. atrox , and was not a different gender due to rarity . Allosaurus atrox was originally named by Marsh in 1878 as the type species of its own genus , Creosaurus , and is based on YPM 1890 , an assortment of bones including a couple of pieces of the skull , portions of nine tail vertebrae , two hip vertebrae , an <unk> , and ankle and foot bones . Although the idea of two common Morrison allosaur species has had support in semi @-@ technical and popular works , it has generally been rejected in the technical literature . 
 David K. Smith , examining Allosaurus fossils by quarry , found that the Cleveland Lloyd Dinosaur <unk> ( Utah ) specimens are generally smaller than those from <unk> Bluff ( Wyoming ) or <unk> Young University 's Dry Mesa <unk> ( Colorado ) , but the shapes of the bones themselves did not vary between the sites . A later study by Smith incorporating Garden Park ( Colorado ) and Dinosaur National Monument ( Utah ) specimens found no justification for multiple species based on skeletal variation ; skull variation was most common and was <unk> , suggesting individual variation was responsible . Further work on size @-@ related variation again found no consistent differences , although the Dry Mesa material tended to clump together on the basis of the <unk> , an ankle bone . Kenneth Carpenter , using skull elements from the Cleveland Lloyd site , found wide variation between individuals , calling into question previous species @-@ level distinctions based such features as the shape of the horns , and the proposed differentiation of " A. jimmadseni " based on the shape of the jugal . 
 
 = = <unk> and synonymous species = = 
 
 A number of species assigned to Allosaurus are no longer recognized as valid , for one reason or another . Species " A. <unk> " , seen in <unk> , 1887 , and <unk> , 1912 , is a typographical error for A. fragilis . Marsh 's A. ferox ( 1896 ; not to be confused with his 1884 Labrosaurus ferox , also part of Allosaurus taxonomy ) was coined for a partial skull in a footnote , and has been recognized as a specimen of A fragilis . A. lucaris , another Marsh name , was given to a partial skeleton in 1878 . He later decided it warranted its own genus , Labrosaurus , but this has not been accepted , and A. lucaris is also regarded as another specimen of A. fragilis . Allosaurus lucaris , is known mostly from vertebrae , sharing characters with Allosaurus . Paul and Carpenter stated that the type specimen of this species , YPM 1931 , was from a younger age than Allosaurus , and might represent a different genus . However , they found that the specimen was <unk> , and thus A. lucaris was a nomen dubium . " A. <unk> " , an informally described species coined by Pickering in 1996 , is a <unk> of the A. atrox versus A. fragilis debate using a better specimen to represent the A. atrox form , and has not been recognized . 
 Several species coined in genera other than Allosaurus are also now thought to be synonymous with A. fragilis . Labrosaurus ferox was named in 1884 by Marsh for an oddly formed partial lower jaw , with a prominent gap in the tooth row at the tip of the jaw , and a rear section greatly expanded and turned down . Later researchers suggested that the bone was <unk> , showing an injury to the living animal , and that part of the unusual form of the rear of the bone was due to plaster reconstruction . It is recognized as most likely a specimen of A. fragilis . Allosaurus valens is a <unk> for <unk> valens accidentally used by Friedrich von <unk> in 1932 ; <unk> valens itself may also <unk> to Allosaurus fragilis , as Gilmore suggested in 1920 . <unk> <unk> , based on a scrap of <unk> Marsh first thought to be a mammalian jaw , may or may not be the same as Allosaurus . 
 
 = = <unk> species = = 
 
 Several species initially classified within or referred to Allosaurus do not belong within the genus . A. medius was named by Marsh in 1888 for " various specimens " from the Early Cretaceous of Maryland , although most of the remains were removed by Richard <unk> Lull to the new ornithopod species <unk> <unk> , except for a tooth . Gilmore considered the tooth <unk> but transferred it to a new species , <unk> medius . The referral was not accepted in the most recent review , and Allosaurus medius was simply listed as a dubious species of theropod . Allosaurus <unk> was described in 1914 by A. N. <unk> on the basis of a bone , later identified as a partial fourth <unk> , from the Early Cretaceous of <unk> , Russia . It was transferred to <unk> in 1990 . 
 Allosaurus <unk> was described in 1870 by <unk> as a species of Megalosaurus , based on a tooth from the Late Jurassic of Switzerland . It has occasionally been referred to Allosaurus , but recent reviews have listed it as dubious theropod species Megalosaurus <unk> , or included it in Ceratosaurus sp . Allosaurus stechowi was described in 1920 by <unk> as Labrosaurus stechowi for isolated Ceratosaurus @-@ like teeth from the <unk> beds of Tanzania . With the <unk> of Labrosaurus and Allosaurus , Donald F. <unk> listed it as a species of Allosaurus , but it is now either assigned to Ceratosaurus sp. or considered a dubious <unk> . 
 There are also several species left over from the <unk> of Creosaurus and Labrosaurus with Allosaurus . Creosaurus <unk> was named by Lull in 1911 for a <unk> from the Early Cretaceous of Maryland . It is now regarded as a dubious theropod . Labrosaurus fragilis is a typographical error by Marsh ( 1896 ) for Labrosaurus ferox . L. <unk> , named by Marsh in 1896 for a Morrison theropod tooth , which like L. stechowi is now regarded as either Ceratosaurus sp. or a dubious <unk> . 
 A. tendagurensis was named in 1925 by Werner <unk> for a partial <unk> ( <unk> 67 ) found in the Kimmeridgian @-@ age rocks of <unk> , in <unk> , Tanzania . This species has not had strong support in recent years , with opinions on its identity ranging from a tentatively valid species of Allosaurus , to a basal tetanuran . The most recent analysis has placed it in <unk> . Although obscure , it was a large theropod , possibly around 10 meters long ( 33 ft ) and 2 @.@ 5 metric tons ( 2 @.@ 8 short tons ) in weight . 
 
 = = Specimens <unk> to Allosaurus though not described as new species = = 
 
 <unk> and colleagues in 2003 designated six teeth from Siberia as Allosaurus sp . ( meaning the authors found the specimens to be most like those of Allosaurus , but did not or could not assign a species ) . Also , reports of Allosaurus in Shanxi , China go back to at least 1982 . 
 An <unk> ( ankle bone ) thought to belong to a species of Allosaurus was found at Cape Paterson , Victoria in Early Cretaceous beds in southeastern Australia . It was thought to provide evidence that Australia was a <unk> for animals that had gone extinct elsewhere . This identification was challenged by Samuel Welles , who thought it more resembled that of an <unk> , but the original authors defended their identification . With fifteen years of new specimens and research to look at , Daniel Chure <unk> the bone and found that it was not Allosaurus , but could represent an <unk> . Similarly , <unk> <unk> and Phil <unk> , in their description of <unk> , noted that the bone closely resembled that of their new genus . This specimen is sometimes referred to as " Allosaurus <unk> " , an informal museum name . It may have belonged to something similar to , or the same as , <unk> , or it may represent an <unk> . A speculative " polar " or " dwarf allosaur " was used for the " Spirits of the Ice Forest " episode of Walking with Dinosaurs . 
 
 