Allosaurus 1347 224189008 2008-07-07T18:53:43Z FunkMonk 4280259 Moved to correct section. {{taxobox | name=''Allosaurus'' | fossil_range = [[Late Jurassic]] | image = Allosaurus-crane.jpg | image_width = 200px | image_caption = Replica of an ''Allosaurus fragilis'' skull. | regnum = [[Animal]]ia | phylum = [[Chordate|Chordata]] | classis = [[Reptile|Sauropsida]] | superordo = [[Dinosaur]]ia | ordo = [[Saurischia]] | subordo = [[Theropoda]] | infraordo = [[Carnosauria]] | familia = [[Allosauridae]] | genus = '''''Allosaurus''''' | genus_authority = [[Othniel Charles Marsh|Marsh]], 1877 | subdivision_ranks = [[Species]] | subdivision = *''A. fragilis'' <small>Marsh, 1877 ([[Type (biology)|type]])</small> *?''A. europaeus'' <small>Mateus ''et al.'', 2006</small> *''A.'' "jimmadseni" <small>Chure, 2000 ''vide'' [[Donald F. Glut|Glut]], 2003 (''[[nomen nudum]]'')</small> *?''A. tendagurensis'' <small>[[Werner Janensch|Janensch]], 1925 | synonyms = *''Creosaurus'' <small>Marsh, 1878</small> *''Labrosaurus'' <small>Marsh, 1879</small> *?''[[Antrodemus]]'' <small>[[Joseph Leidy|Leidy]], 1870</small> *?''[[Apatodon]]'' <small>Marsh, 1877</small> *?''[[Epanterias]]'' <small>[[Edward Drinker Cope|Cope]], 1878</small> }} '''''Allosaurus''''' ({{pronEng|ˌæləˈsɔrəs}}) is a [[genus]] of large [[theropod]] [[dinosaur]] that lived 155 to 145 million years ago, in the [[late Jurassic]] [[Period (geology)|period]]. The first remains that can definitely be ascribed to this genus were described in 1877 by [[Othniel Charles Marsh]]. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of [[paleontology|paleontological]] circles, and has been a lead dinosaur in several [[film]]s and [[documentary film|documentaries]]. ''Allosaurus'' was a large [[biped]]al [[predation|predator]] with a large skull, equipped with dozens of large, sharp [[teeth]]. It averaged 8.5&nbsp;[[metre|meters]] (30&nbsp;ft) in length, though fragmentary remains suggest it could have reached over 12&nbsp;meters (39&nbsp;ft). Relative to the large and powerful hindlimbs, its three-fingered forelimbs were small, and the body was balanced by a long, heavy tail. It is classified as an [[allosaurid]], a type of carnosaurian theropod dinosaur. The genus has a complicated [[taxonomy]], and includes an uncertain number of valid [[species]], the best known of which is ''A. fragilis''. The bulk of ''Allosaurus'' remains have come from [[North America]]'s [[Morrison Formation]], with material also from [[Portugal]] and possibly [[Tanzania]]. It was known for over half of the 20th century as ''[[Antrodemus]]'', but study of the copious remains from the [[Cleveland Lloyd Dinosaur Quarry]] brought the name ''Allosaurus'' back to prominence, and established it as one of the best-known dinosaurs. As the prominent large predator in the [[Morrison Formation]], ''Allosaurus'' was at the top of the [[food chain]], probably preying on contemporaneous large herbivorous dinosaurs. Potential prey included [[ornithopod]]s, [[stegosaurid]]s, and [[sauropod]]s. While it is often thought of as preying on sauropod dinosaurs in groups, there is little evidence for cooperative [[social behavior]] in this genus, and individuals may have been aggressive toward each other instead. It may have attacked large prey by ambush, using its upper jaws like a [[hatchet]]. == Description == [[Image:Allosaurus size comparison.svg|thumb|left|The size range of ''Allosaurus'', compared with a human.]] ''Allosaurus'' was a typical large theropod, having a massive [[skull]] on a short [[neck]], a long [[tail]] and reduced forelimbs. ''Allosaurus fragilis'', the best-known species, had an average length of 8.5&nbsp;meters (28&nbsp;ft),<ref name=DFG97>{{cite book|chapter=Allosaurus |last=Glut |first=Donald F. |title=Dinosaurs: The Encyclopedia |year=1997 |publisher=McFarland & Co |location=Jefferson, North Carolina |pages=105–117 |isbn=0-89950-917-7}}</ref> with the largest definitive ''Allosaurus'' specimen ([[American Museum of Natural History|AMNH]] 680) estimated at 9.7&nbsp;meters long (32&nbsp;ft),<ref name=MMDML03>{{cite web |publisher=The Dinosaur Mailing List |url=http://dml.cmnh.org/2003Jul/msg00355.html |title=And the Largest Theropod Is.... |last=Mortimer |first=Mickey |date=[[2003-07-21]] |accessdate=2007-09-08}}</ref> and an estimated weight of 2.3&nbsp;[[metric ton]]s (2.5&nbsp;[[short ton]]s).<ref name=MMDML03/> In his 1976 [[monograph]] on ''Allosaurus'', James Madsen mentioned a range of bone sizes which he interpreted to show a maximum length of 12 to 13&nbsp;meters (40 to 43&nbsp;ft).<ref name=JM76>{{cite book |last=Madsen |first=James H., Jr. |origyear=1976 |year=1993 |title=''Allosaurus fragilis'': A Revised Osteology |series=Utah Geological Survey Bulletin '''109''' |publisher=Utah Geological Survey |location=Salt Lake City |edition=2nd ed.}}</ref> As with dinosaurs in general, weight estimates are debatable, and since 1980 have ranged between 1500&nbsp;kilograms (3300&nbsp;lb), 1000 to 4000&nbsp;kilograms (2200 to 8800&nbsp;lb), and 1010&nbsp;kilograms (2230&nbsp;lb) for [[mode (statistics)|modal]] adult weight (not maximum).<ref name=JRF03>{{cite book |last=Foster |first=John R. |year=2003 |title=Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque |series= New Mexico Museum of Natural History and Science Bulletin '''23''' |pages=p. 37}}</ref> John Foster, a specialist on the Morrison Formation, suggests that 1000&nbsp;kg (2200&nbsp;lb) is reasonable for large adults of ''A. fragilis'', but that 700&nbsp;kg (1500&nbsp;lb) is a closer estimate for individuals represented by the average-sized [[femur|thigh bones]] he has measured.<ref name=JF07>{{cite book |last=Foster | first=John |title=Jurassic West: the Dinosaurs of the Morrison Formation and Their World |chapter=''Allosaurus fragilis'' |pages=170-176 |publisher=Indiana University Press |location=Bloomington, Indiana |isbn=978-0-253-34870-8}}</ref> Several gigantic specimens have been attributed to ''Allosaurus'', but may in fact belong to other genera. The closely related genus ''[[Saurophaganax]]'' ([[Sam Noble Oklahoma Museum of Natural History|OMNH]] 1708) reached perhaps 10.9&nbsp;meters (36&nbsp;ft) in length,<ref name=MMDML03/> and its single species has sometimes been included in the genus ''Allosaurus'' as ''Allosaurus maximus'', though recent studies support it as a separate genus.<ref name=DJC00>{{cite book |last=Chure |first=Daniel J. |year=2000 |title=A new species of ''Allosaurus'' from the Morrison Formation of Dinosaur National Monument (Utah–Colorado) and a revision of the theropod family Allosauridae |series=Ph.D. dissertation |publisher=Columbia University}}</ref> Another potential specimen of ''Allosaurus'', once assigned to the genus ''[[Epanterias]]'' (AMNH 5767), may have measured 12.1&nbsp;meters in length (40&nbsp;ft).<ref name=MMDML03/> A more recent discovery is a partial skeleton from the Peterson Quarry in Morrison rocks of [[New Mexico]]; this large allosaurid may be another individual of ''Saurophaganx''.<ref name=JF07b>Foster, John. 2007. ''Jurassic West: the Dinosaurs of the Morrison Formation and Their World.'' Bloomington, Indiana:Indiana University Press. p. 117.</ref> ===Skull=== [[Image:Allosaur (1768858002).jpg|thumb|Skull of mounted ''Allosaurus'' skeleton at the San Diego Natural History Museum.]] The skull and teeth of ''Allosaurus'' were modestly proportioned for a theropod of its size. Paleontologist [[Gregory S. Paul]] gives a length of 845&nbsp;[[millimetre|millimeters]] (33.3&nbsp;in) for a skull belonging to an individual he estimates at 7.9&nbsp;meters long (26&nbsp;ft).<ref name=GSP88>{{cite book |last=Paul |first=Gregory S. |title=Predatory Dinosaurs of the World |year=1988 |publisher=Simon & Schuster |location=New York |isbn=0-671-61946-2 |chapter=Genus ''Allosaurus'' |pages=pp. 307–313 }}</ref> Each [[premaxilla]] (the bones that formed the tip of the snout), held five teeth with D-shaped cross-sections, and each [[maxilla]] (the main tooth-bearing bones in the upper jaw) had between fourteen and seventeen teeth; the number of teeth does not exactly correspond to the size of the bone. Each [[dentary]] (the tooth-bearing bone of the lower jaw) had between fourteen and seventeen teeth, with an average count of sixteen. The teeth became shorter, more narrow, and more curved toward the back of the skull. All of the teeth had saw-like edges. They were shed easily, and were replaced continually, making them common fossils.<ref name=JM76/> The skull had a pair of [[horn (anatomy)|horns]] above and in front of the eyes. These horns were composed of extensions of the [[lacrimal bone]]s,<ref name=JM76/> and varied in shape and size. There were also lower paired ridges running along the top edges of the [[nasal bone]]s that led into the horns.<ref name=JM76/> The horns were probably covered in a [[keratin]] sheath and may have had a variety of functions, including acting as sunshades for the eye,<ref name=JM76/> being used for display, and being used in combat against other members of the same species<ref name=REM77>{{cite journal |last=Molnar |first=Ralph E. |authorlink=Ralph Molnar |year=1977 |title=Analogies in the evolution of combat and display structures in ornithopods and ungulates |journal=Evolutionary Theory |volume=3 |pages=165–190}}</ref><ref name=GSP88/> (although they were fragile).<ref name=JM76/> There was a ridge along the back of the skull roof for muscle attachment, as is also seen in [[tyrannosauridae|tyrannosaurids]].<ref name=GSP88/> Inside the lacrimal bones were depressions that may have held [[gland]]s, such as [[salt gland]]s.<ref name=DBN85>{{cite book |last=Norman |first=David B. |authorlink=David B. Norman |title=The Illustrated Encyclopedia of Dinosaurs: An Original and Compelling Insight into Life in the Dinosaur Kingdom |chapter='Carnosaurs' |year=1985 |publisher=Crescent Books |location=New York |pages=62–67 |isbn=0-517-468905 }}</ref> Within the maxillae were [[Maxillary sinus|sinus]]es that were better developed than those of more [[basal (phylogenetics)|basal]] theropods such as ''[[Ceratosaurus]]'' and ''[[Marshosaurus]]''; they may have been related to the [[sense of smell]], perhaps holding something like [[vomeronasal organ|Jacobson's organ]]. The roof of the braincase was thin, perhaps to improve [[thermoregulation]] for the [[brain]].<ref name=JM76/> The skull and lower jaws had joints that permitted motion within these units. In the lower jaws, the bones of the front and back halves loosely articulated, permitting the jaws to bow outward and increasing the animal's gape.<ref name=GSP88e>Paul, Gregory S. (1988). ''Predatory Dinosaurs of the World''. 91 and Figure 4–5 (93).</ref> The [[braincase]] and [[frontal bone|frontals]] may also have had a joint.<ref name=JM76/> ===Postcranial skeleton=== [[Image:Allosaurus SDNHM.jpg|thumb|left|''Allosaurus fragilis'' skeleton mounted in the lobby of the [[San Diego Natural History Museum]].]] ''Allosaurus'' had nine [[vertebra]]e in the neck, fourteen in the back, and five in the [[sacrum]] supporting the hips.<ref>Madsen, 1976; note that not everyone agrees on where the neck ends and the back begins, and some authors such as Gregory S. Paul interpret the count as ten neck and thirteen back vertebrae.</ref> The number of tail vertebrae is unknown and varied with individual size; James Madsen estimated about 50,<ref name=JM76/> while Gregory S. Paul considered that to be too many and suggested 45 or less.<ref name=GSP88/> There were hollow spaces in the neck and [[anatomical terms of location|anterior]] back vertebrae.<ref name=JM76/> Such spaces, which are also found in modern theropods (that is, the birds), are interpreted as having held [[Bird anatomy#Respiratory system|air sac]]s used in [[respiratory system|respiration]].<ref name=HMC04>{{cite book|last=Holtz |first=Thomas R., Jr. |authorlink=Thomas R. Holtz, Jr. |coauthors=Molnar, Ralph E.; and Currie, Philip J. |year=2004 |editor=Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.)|title=The Dinosauria |edition=2nd ed. |publisher=University of California Press |location=Berkeley |isbn=0-520-24209-2 |pages=71–110 }}</ref> The rib cage was broad, giving it a barrel chest, especially in comparison to less [[derived]] theropods like ''Ceratosaurus''.<ref name=GSP88b>Paul, Gregory S. (1988). ''Predatory Dinosaurs of the World''. 277.</ref> ''Allosaurus'' had [[gastralium|gastralia]] (belly ribs), but these are not common findings,<ref name=JM76/> and they may have [[ossification|ossified]] poorly.<ref name=GSP88/> In one published case, the gastralia show evidence of injury during life.<ref name=DJC00b>{{cite journal |last=Chure |first=Daniel J. |year=2000 |title=Observations on the morphology and pathology of the gastral basket of ''Allosaurus'', based on a new specimen from Dinosaur National Monument |journal=Oryctos |volume=3 |pages=39–37|issn=1290-4805}}</ref> A [[furcula]] (wishbone) was also present, but has only been recognized since 1996; in some cases furculae were confused with gastralia.<ref name=CM96>{{cite journal |last=Chure |first=Daniel J. |coauthors=and Madsen, James H. |year=1996 |title=On the presence of furculae in some non-maniraptoran theropods |journal=Journal of Vertebrate Paleontology |volume=16| issue=3 |pages=573–577}}</ref><ref name=DJC00b/> The [[ilium (bone)|ilium]], the main hip bone, was massive, and the [[pubis (bone)|pubic bone]] had a prominent foot that may have been used for both muscle attachment and as a prop for resting the body on the ground. Madsen noted that in about half of the individuals from the Cleveland Lloyd Dinosaur Quarry, independent of size, the pubes had not fused to each other at their foot ends. He suggested that this was a [[sexual dimorphism|sexual characteristic]], with females lacking fused bones to make egg-laying easier.<ref name=JM76/> This proposal has not attracted further attention, however. [[Image:Allosaurus fragilis.jpg|thumb|Claw of ''Allosaurus fragilis''.]] The forelimbs of ''Allosaurus'' were short in comparison to the hindlimbs (only about 35% the length of the hindlimbs in adults)<ref name=MG98>{{cite journal |last=Middleton |first=Kevin M. |coauthors=and Gatesy, Stephen M. |year=2000 |title=Theropod forelimb design and evolution |journal=Zoological Journal of the Linnean Society |volume=128 |pages=149–187 |doi=10.1006/zjls.1998.0193 |url=http://www.brown.edu/Departments/EEB/EML/files/kevin_zjls00.pdf |accessdate=2007-10-25}}</ref> and had three fingers per hand, tipped with large, strongly curved and pointed claws.<ref name=JM76/> The arms were powerful,<ref name=GSP88/> and the forearm was somewhat shorter than the upper arm (1:1.2&nbsp;[[humerus]]/[[ulna]] ratio).<ref name=CWG20>{{cite journal |last=Gilmore |first=Charles W. |authorlink=Charles W. Gilmore |year=1920 |title=Osteology of the carnivorous dinosauria in the United States National Museum, with special reference to the genera ''Antrodemus'' (''Allosaurus'') and ''Ceratosaurus'' |journal=Bulletin of the United States National Museum |volume=110 |pages=1–159}}</ref> The wrist had a version of the semilunate [[carpus|carpal]]<ref name=KC02/> also found in more derived theropods like [[maniraptora]]ns. Of the three fingers, the innermost (or [[thumb]]) was the largest,<ref name=GSP88/> and diverged from the others.<ref name=CWG20/> The legs were not as long or suited for speed as those of [[tyrannosaurid]]s, and the claws of the toes were less developed and more [[hoof]]-like than those of earlier theropods.<ref name=GSP88/> Each foot had three weight-bearing toes and an inner [[dewclaw]], which Madsen suggested could have been used for grasping in juveniles.<ref name=JM76/> There was also what is interpreted as the splint-like remnant of a fifth (outermost) [[metatarsus|metatarsal]], perhaps used as a lever between the [[Achilles tendon]] and foot.<ref name=GSP88d>Paul, Gregory S. (1988). ''Predatory Dinosaurs of the World''. 113; note illustrations of ''Allosaurus'' on 310 and 311 as well; Madsen (1976) interpreted these bones as possible upper portions of the inner metatarsal.</ref> ==Classification== [[Image:Allosaurus BW.jpg|thumb|left|Life restoration of ''Allosaurus fragilis''.]] ''Allosaurus'' was an allosaurid, a member of a [[family (biology)|family]] of large theropods within the larger group [[Carnosauria]]. The family name [[Allosauridae]] was created for this genus in 1878 by [[Othniel Charles Marsh]],<ref name=OCM78>{{cite journal |last=Marsh |first=Othniel Charles |year=1878 |title=Notice of new dinosaurian reptiles |journal=American Journal of Science and Arts |volume=15 |pages=241–244}}</ref> but the term was largely unused until the 1970s in favor of [[Megalosauridae]], another family of large theropods that eventually became a [[wastebasket taxon]]. This, along with the use of ''Antrodemus'' for ''Allosaurus'' during the same period, is a point that needs to be remembered when searching for information on ''Allosaurus'' in publications that predate James Madsen's 1976 monograph. Major publications using the name Megalosauridae instead of Allosauridae include [[Charles Gilmore|Gilmore]], 1920,<ref name=CWG20/> [[Friedrich von Huene|von Huene]], 1926,<ref name=FvH26>{{cite journal |last=von Huene |first=Friedrich |year=1926 |title=The carnivorous Saurischia in the Jura and Cretaceous formations, principally in Europe |journal=Revista del Museo de La Plata |volume=29 |pages=35–167}}</ref> [[Alfred Sherwood Romer|Romer]], 1956 and 1966,<ref name=ASR56>{{cite book |last=Romer |first=Alfred S. |year=1956 |title=Osteology of the Reptiles |publisher=University of Chicago Press |location=Chicago |pages=772pp |isbn=0-89464985-X}}</ref><ref name=ASR66>{{cite book |last=Romer |first=Alfred S. |title= Vertebrate Paleontology |edition=Third Edition |year=1966 |publisher= University of Chicago Press |location= Chicago |pages= 468 pp.|isbn=0-7167-1822-7}}</ref> Steel, 1970,<ref name="Steel70">{{cite journal|last=Steel|first=R.|year= 1970|title=Part 14. Saurischia. Handbuch der Paläoherpetologie/Encyclopedia of Paleoherpetology|journal= Gustav Fischer Verlag, Stuttgart|pages=1–87}}</ref> and [[Alick Walker|Walker]], 1964.<ref name=ADW64>{{cite journal |last=Walker |first=Alick D. |year=1964 |title=Triassic reptiles from the Elgin area: ''Ornithosuchus'' and the origin of carnosaurs |journal=Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences |volume=248 |pages=53–134 |url=http://links.jstor.org/sici?sici=0080-4622(19641126)248:744%3C53:TRFTEA%3E2.0.CO;2-K |issue=744 |doi=10.1098/rstb.1964.0009}}</ref> Following the publication of Madsen's influential monograph, Allosauridae became the preferred family assignment, but it too was not strongly defined. Semi-technical works used Allosauridae for a variety of large theropods, usually those that were larger and better-known than megalosaurids. Typical theropods that were thought to be related to ''Allosaurus'' included ''[[Indosaurus]]'', ''[[Piatnitzkysaurus]]'', ''[[Piveteausaurus]]'', ''[[Yangchuanosaurus]]'',<ref name=DL83>{{cite book |last=Lambert |first=David |coauthors=and the Diagram Group |title=A Field Guide to Dinosaurs |year=1983 |publisher=Avon Books |location=New York |isbn=0-380-83519-3 |chapter=Allosaurids |pages=80–81}}</ref> ''[[Acrocanthosaurus]]'', ''[[Chilantaisaurus]]'', ''[[Compsosuchus]]'', ''[[Stokesosaurus]]'', and ''[[Szechuanosaurus]]''.<ref name=DL90>{{cite book |last=Lambert |first=David |coauthors=and the Diagram Group |title=The Dinosaur Data Book |year=1990 |publisher=Avon Books |location=New York |isbn=0-380-75896-3 |chapter=Allosaurids |pages=130}}</ref> Given modern knowledge of theropod diversity and the advent of cladistic study of [[evolution]]ary relationships, none of these theropods is now recognized as an allosaurid, although several, like ''Acrocanthosaurus'' and ''Yangchuanosaurus'', are members of related families.<ref name=HMC04/> Allosauridae is one of three families in Carnosauria; the other two are [[Carcharodontosauridae]] and [[Sinraptoridae]].<ref name=HMC04/> Allosauridae has at times been proposed as ancestral to the [[Tyrannosauridae]] (which would make it [[paraphyly|paraphyletic]]), one recent example in Gregory S. Paul's ''Predatory Dinosaurs of the World'',<ref name=GSP88c>Paul, Gregory S. (1988). "The allosaur-tyrannosaur group", ''Predatory Dinosaurs of the World''. 301–347.</ref> but this has been rejected, with tyrannosaurids identified as members of a separate branch of theropods, the [[Coelurosauria]].<ref name=TRHJ94>{{cite journal|last=Holtz |first=Thomas R., Jr. |year= 1994 |title=The phylogenetic position of the Tyrannosauridae: implications for theropod systematics |journal=Journal of Paleontology |volume=68 |issue=5 |pages=1100–1117 |url=http://links.jstor.org/sici?sici=0022-3360(199409)68:5%3C1100:TPPOTT%3E2.0.CO;2-R}}</ref> Allosauridae is the smallest of the carnosaur families, with only ''Saurophaganax'' and a currently unnamed [[France|French]] [[allosauroidea|allosauroid]] accepted as possible valid [[genus|genera]] besides ''Allosaurus'' in the most recent review.<ref name=HMC04/> Another genus, ''Epanterias'', is a potential valid member, but it and ''Saurophaganax'' may turn out to be large examples of ''Allosaurus''.<ref name=GSP88/> Recent reviews have kept the genus ''Saurophaganax'' and included ''Epanterias'' with ''Allosaurus''.<ref name=JRF03/><ref name=HMC04/> == Discovery and history == ===Early discoveries and research=== The discovery and early study of ''Allosaurus'' is complicated by the multiplicity of names coined during the [[Bone Wars]] of the late 1800s. The first described [[fossil]] in this history was a bone obtained secondhand by [[Ferdinand Vandiveer Hayden]] in 1869. It came from [[Middle Park (Colorado basin)|Middle Park]], near [[Granby, Colorado]], probably from [[Morrison Formation]] rocks. The locals had identified such bones as "petrified [[horse]] hoofs". Hayden sent his specimen to [[Joseph Leidy]], who identified it as half of a tail vertebra, and tentatively assigned it to the European dinosaur genus ''[[Poekilopleuron]]'' as ''Poicilopleuron'' [sic] ''valens''.<ref name=JL70>{{cite journal |last=Leidy |first=Joseph |year=1870 |title=Remarks on ''Poicilopleuron valens'', ''Clidastes intermedius'', ''Leiodon proriger'', ''Baptemys wyomingensis'', and ''Emys stevensonianus'' |journal=Proceedings of the Academy of Natural Sciences, Philadelphia |volume=22 |pages=3–4}}</ref> He later decided it deserved its own genus, ''Antrodemus''.<ref name=JL73>{{cite journal |last=Leidy |first=Joseph |year=1873 |title=Contribution to the extinct vertebrate fauna of the western territories |journal=Report of the U.S. Geological Survey of the Territories I |pages=14–358}}</ref> ''Allosaurus'' itself is [[holotype|based on]] [[Peabody Museum of Natural History|YPM]] 1930, a small collection of fragmentary bones including parts of three vertebrae, a rib fragment, a tooth, a toe bone, and, most useful for later discussions, the shaft of the right humerus (upper arm). Othniel Charles Marsh gave these remains the formal name ''Allosaurus fragilis'' in 1877. ''Allosaurus'' comes from the [[Ancient Greek|Greek]] ''allos/αλλος'', meaning "strange" or "different" and ''saurus/σαυρος'', meaning "lizard" or "reptile".<ref>{{cite book|author=Liddell & Scott|year=1980|title=Greek–English Lexicon, Abridged Edition |publisher=Oxford University Press| location=Oxford|isbn= 0-19-910207-4}}</ref> It was named 'different lizard' because its vertebrae were different from those of other dinosaurs known at the time of its discovery.<ref name=OCM77>{{cite journal |last=Marsh |first=Othniel Charles |year=1877 |title=Notice of new dinosaurian reptiles from the Jurassic formation |journal=American Journal of Science and Arts |volume=14 |pages=514–516}}</ref><ref name=DMLomnipedia>{{cite web |url=http://www.dinosauria.com/dml/names/dinoa.htm |title=Dinosauria Translation and Pronunciation Guide A |accessdate=2007-09-11 |author=Creisler, Ben |date=2003-07-07 |publisher=Dinosauria On-Line}}</ref> The species epithet ''fragilis'' is [[Latin]] for "fragile", referring to lightening features in the vertebrae. The bones were collected from the Morrison Formation of [[Garden Park, Colorado|Garden Park]], north of [[Cañon City, Colorado|Cañon City]].<ref name=OCM77/> Marsh and [[Edward Drinker Cope]], who were in scientific competition, went on to coin several other genera based on similarly sparse material that would later figure in the taxonomy of ''Allosaurus''. These include Marsh's ''Creosaurus''<ref name=OCM78/> and ''Labrosaurus'',<ref name=OCM79>{{cite journal |last=Marsh |first=Othniel Charles |year=1879 |title=Principal characters of American Jurassic dinosaurs. Part II |journal=American Journal of Science, Series 3 |volume=17 |pages=86–92}}</ref> and Cope's ''Epanterias''.<ref name=EDC78>{{cite journal |last=Cope |first=Edward Drinker |year=1878 |title=A new opisthocoelous dinosaur |journal=American Naturalist |volume=12 |issue=6 |pages=406}}</ref> [[Image:AllosaurusAMNH5753.jpg|thumb|left|The skeletal mount of AMNH 5753, posed as scavenging an ''[[Apatosaurus]]''.]] [[Image:Allosaurus4.jpg|thumb|left|AMNH 5753 in a [[Charles R. Knight]] life restoration.]] In their haste, Cope and Marsh did not always follow up on their discoveries (or, more commonly, those made by their subordinates). For example, after the discovery by [[Benjamin Franklin Mudge|Benjamin Mudge]] of the type specimen of ''Allosaurus'' in Colorado, Marsh elected to concentrate work in [[Wyoming]]; when work resumed at Garden Park in 1883, M. P. Felch found an almost complete ''Allosaurus'' and several partial skeletons.<ref name=DBN85/> In addition, one of Cope's collectors, H. F. Hubbell, found a specimen in the [[Como Bluff]] area of Wyoming in 1879, but apparently did not mention its completeness, and Cope never unpacked it. Upon unpacking in 1903 (several years after Cope had died), it was found to be one of the most complete theropod specimens then known, and in 1908 the skeleton, now cataloged as AMNH 5753, was put on public view.<ref name=NGD95>{{cite book |last=Norell |first=Mark A. |coauthors=Gaffney, Eric S.; and Dingus, Lowell |title=Discovering Dinosaurs in the American Museum of Natural History |publisher=Knopf |location=New York |year=1995 |pages=112–113 |isbn=0-679-43386-4}}</ref> This is the well-known mount poised over a partial ''[[Apatosaurus]]'' skeleton as if [[scavenger|scavenging]] it, illustrated as such by Charles R. Knight. Although notable as the first free-standing mount of a theropod dinosaur, and often illustrated and photographed, it has never been scientifically described.<ref name=BBetal99>{{cite journal |last=Breithaupt |first=Brent H. |coauthors=Chure, Daniel J.; and Southwell, Elizabeth H. |year=1999 |title=AMNH 5753: the world's first free-standing theropod skeleton |journal=Journal of Vertebrate Paleontology |volume=19 |issue=3, Suppl. |pages=33A}}</ref> [[Image:Dinosaur.jpg|thumb|Recent picture of AMNH 5753]] The multiplicity of early names complicated later research, with the situation compounded by the terse descriptions provided by Marsh and Cope. Even at the time, authors such as [[Samuel Wendell Williston]] suggested that too many names had been coined.<ref name=SWW78>{{cite journal |last=Williston |first=Samuel Wendell |year=1878 |title=American Jurassic dinosaurs |journal=Transactions of the Kansas Academy of Science |volume=6 |pages=42–46}}</ref> For example, Williston pointed out in 1901 that Marsh had never been able to adequately distinguish ''Allosaurus'' from ''Creosaurus''.<ref name=SWW01>{{cite journal |last=Williston |first=Samuel Wendell |year=1901 |title=The dinosaurian genus ''Creosaurus'', Marsh |journal=American Journal of Science, series 4 |volume=11 |issue=11 |pages=111–114}}</ref> The most influential early attempt to sort out the convoluted situation was produced by [[Charles W. Gilmore]] in 1920. He came to the conclusion that the tail vertebra dubbed ''Antrodemus'' by Leidy was indistinguishable from those of ''Allosaurus'', and ''Antrodemus'' thus should be the preferred name because as the older name it had priority.<ref name=CWG20/> ''Antrodemus'' became the accepted name for this familiar genus for over fifty years, until James Madsen published on the Cleveland-Lloyd specimens and concluded that ''Allosaurus'' should be used because ''Antrodemus'' was based on material with poor, if any, diagnostic features and locality information (for example, the [[geological formation]] that the single bone of ''Antrodemus'' came from is unknown).<ref name=JM76/> "''Antrodemus''" has been used informally for convenience when distinguishing between the skull Gilmore restored and the composite skull restored by Madsen.<ref name=DH98>{{cite journal |last=Henderson |first=Donald M. |year=1998 |title=Skull and tooth morphology as indicators of niche partitioning in sympatric Morrison Formation theropods |journal=Gaia |volume=15 |pages=219–266 |url=http://www.mnhn.ul.pt/geologia/gaia/16.pdf |issn=0871-5424 |format=pdf}}</ref> ===Cleveland-Lloyd discoveries=== Although sporadic work at what became known as the [[Cleveland-Lloyd Dinosaur Quarry]] in [[Emery County, Utah|Emery County]], [[Utah]] had taken place as early as 1927, and the fossil site itself described by [[William J. Stokes]] in 1945,<ref name=WJS45>{{cite journal |last=Stokes |first=William J. |year=1945 |title=A new quarry for Jurassic dinosaurs |journal=Science |volume=101 |issue=2614 |pages=115–117 |doi=10.1126/science.101.2614.115-a |pmid=17799203}}</ref> major operations did not begin there until 1960. Under a cooperative effort involving nearly 40&nbsp;institutions, thousands of bones were recovered between 1960 and 1965.<ref name=JM76/> The quarry is notable for the predominance of ''Allosaurus'' remains, the condition of the specimens, and the lack of scientific resolution on how it came to be. The majority of bones belong to the large theropod ''Allosaurus fragilis'' (it is estimated that the remains of at least 46&nbsp;''A. fragilis'' have been found there, out of at minimum 73&nbsp;dinosaurs), and the fossils found there are disarticulated and well-mixed. Nearly a dozen scientific papers have been written on the [[taphonomy]] of the site, coming up with numerous contradictory explanations for how it formed. Suggestions have ranged from animals getting stuck in a bog, to becoming trapped in deep mud, to falling victim to [[drought]]-induced mortality around a waterhole, to getting trapped in a spring-fed pond or seep.<ref name=APHetal06>{{cite book |last=Hunt |first=Adrian P |coauthors=Lucas, Spencer G.; Krainer, Karl; and Spielmann, Justin |year=2006 |chapter=The taphonomy of the Cleveland-Lloyd Dinosaur Quarry, Upper Jurassic Morrison Formation, Utah: a re-evaluation |editor=Foster, John R.; and Lucas, Spencer G. (eds.) |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |series=New Mexico Museum of Natural History and Science Bulletin, '''36''' |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque, New Mexico |pages=57–65}}</ref> Regardless of the actual cause, the great quantity of well-preserved ''Allosaurus'' remains has allowed this genus to be known in detail, making it among the best-known theropods. Skeletal remains from the quarry pertain to individuals of almost all ages and sizes, from less than 1&nbsp;meter (3.3&nbsp;ft)<ref name=LSCC03>{{cite journal |last=Loewen |first=Mark A. |coauthors=Sampson, Scott D.; Carrano, Matthew T.; and 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, Suppl. |pages=72A }}</ref> to 12&nbsp;meters (39&nbsp;ft) long, and the disarticulation is an advantage for describing bones usually found fused.<ref name=JM76/> ===Recent work: 1980s–present=== [[Image:Allosaurus-fossilized skull.jpg|thumb|right|''Allosaurus'' skull from [[Dinosaur National Monument]], still partially encased in matrix.]] The period since Madsen's monograph has been marked by a great expansion in studies dealing with topics concerning ''Allosaurus'' in life ([[paleobiology|paleobiological]] and [[paleoecology|paleoecological]] topics). Such studies have covered topics including skeletal variation,<ref name=DKS98>{{cite journal |last=Smith |first=David K. |year=1998 |title=A morphometric analysis of ''Allosaurus'' |journal=Journal of Vertebrate Paleontology |volume=18 |issue=1 |pages=126–142}}</ref> growth,<ref name=PBetal06>{{cite journal |last=Bybee |first=Paul J. |coauthors=Lee, A.H.; and Lamm, E.-T. |year=2006 |title=Sizing the Jurassic theropod dinosaur ''Allosaurus'': assessing growth strategy and evolution of ontogenetic scaling of limbs |journal=Journal of Morphology |volume=267 |issue=3 |pages=347–359 |doi=10.1002/jmor.10406}}</ref><ref name=FC06>{{cite book |last=Foster |first=John R. |coauthors=and Chure, Daniel J. |year=2006 |chapter=Hindlimb allometry in the Late Jurassic theropod dinosaur ''Allosaurus'', with comments on its abundance and distribution |editor=Foster, John R.; and Lucas, Spencer G. (eds.) |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |series=New Mexico Museum of Natural History and Science Bulletin, '''36''' |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque, New Mexico |pages=119–122}}</ref> skull construction,<ref name=ERetal01>{{cite journal |last=Rayfield |first=Emily J. |coauthors=Norman, David B.; Horner, Celeste C.; Horner, John R.; Smith, Paula May; Thomason, Jeffrey J.; and Upchurch, Paul |year=2001 |title=Cranial design and function in a large theropod dinosaur |journal=Nature |volume=409 |pages=1033–1037 |doi=10.1038/35059070}}</ref> hunting methods,<ref name=BB98>{{cite journal |last=Bakker |first=Robert T. |coauthors= |year=1998 |title=Brontosaur killers: Late Jurassic allosaurids as sabre-tooth cat analogues |journal=Gaia |volume=15 |pages=145–158|issn=0871-5424 |url=http://www.mnhn.ul.pt/geologia/gaia/10.pdf |format=pdf}}</ref> the [[brain]],<ref name=SWR99>{{cite journal |last=Rogers |first=Scott W. |year=1999 |title=''Allosaurus'', crocodiles, and birds: evolutionary clues from spiral computed tomography of an endocast |journal=The Anatomical Record |volume=257 |issue=5 |pages=163–173 |url=http://www3.interscience.wiley.com/cgi-bin/fulltext/68500945/PDFSTART |format=pdf |doi=10.1002/(SICI)1097-0185(19991015)257:5<162::AID-AR5>3.0.CO;2-W}}</ref> and the possibility of gregarious living and parental care.<ref name=RTB97>{{cite book |last=Bakker |first=Robert T. |year=1997 |editor=Wolberg, Donald L.; Sump, Edmund; and Rosenberg, Gary D. (eds.) |chapter=Raptor Family values: Allosaur parents brought giant carcasses into their lair to feed their young |title=Dinofest International, Proceedings of a Symposium Held At Arizona State University |publisher=Academy of Natural Sciences |location=Philadelphia |pages=51–63|isbn=0-935868-94-1}}</ref> Reanalysis of old material (particularly of large 'allosaur' specimens),<ref name=GSP88/><ref name=DJC95>{{cite book |last=Chure |first=Daniel J. |year=1995 |chapter=A reassessment of the gigantic theropod ''Saurophagus maximus'' from the Morrison Formation (Upper Jurassic) of Oklahoma, USA |editors=Ailing Sun and Yuangqing Wang (eds.) |title=Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers |publisher=China Ocean Press |location=Beijing |pages=103–106| isbn=7-5027-3898-3}}</ref> new discoveries in Portugal,<ref name=PMetal99>{{cite journal |last=Pérez-Moreno |first=B.P. |coauthors=Chure, D.J.; Pires, C.; Silva, C.M.; Santos, V.; Dantas, P.; Póvoas, L.; Cachão, M.; Sanz, J.L.; and Galopim De Carvalho, A.M. |year=1999 |title=On the presence of ''Allosaurus fragilis'' (Theropoda: Carnosauria) in the Upper Jurassic of Portugal: First evidence of an intercontinental dinosaur species |journal=Journal of the Geological Society |volume=156 |issue=3 |pages=449–452 |doi=10.1144/gsjgs.156.3.0449 |url=http://correio.fc.ul.pt/~cmsilva/Artigos/CMS034.pdf |format=pdf}}</ref> and several very complete new specimens<ref name=BB96>{{cite book |last=Breithaupt |first=Brent |year=1996 |chapter=The discovery of a nearly complete ''Allosaurus'' from the Jurassic Morrison Formation, eastern Bighorn Basin, Wyoming |editors=Brown, C.E.; Kirkwood, S.C.; and Miller, T.S. (eds). |title=Forty-Seventh Annual Field Conference Guidebook |pages=309–313 |publisher=Wyoming Geological Association |location=Casper, Wyoming |oclc=36004754}}</ref><ref name=DJC00b/><ref name=BigAlTwo>{{cite web |url=http://geo-sciences.com/howequarry.htm |title=Howe Dinosaur Quarry – Wyoming’s Jurassic Treasure |accessdate=2007-09-27 |date=2007-07-24 |publisher=GeoScience Adventures}}</ref> have also contributed to the growing knowledge base. ===="Big Al"==== One of the more significant ''Allosaurus'' finds was the 1991 discovery of "Big Al" ([[Museum of the Rockies|MOR]] 693), a 95%&nbsp;complete, partially articulated specimen that measured about 8&nbsp;meters (about 26&nbsp;ft) in length. MOR 693 was excavated near [[Shell, Wyoming]], by a joint Museum of the Rockies and [[University of Wyoming]] Geological Museum team.<ref name=BBbigal>{{cite web |last=Breithaupt |first=Brent H. |url=http://www2.nature.nps.gov/geology/paleontology/pub/fossil_conference_6/breithaupt.htm |title=The case of "Big Al" the ''Allosaurus'': a study in paleodetective partnerships |accessdate=2007-10-03}}</ref> This skeleton was discovered by a Swiss team, led by Kirby Siber. The same team later excavated a second ''Allosaurus'', "Big Al Two", which is the best preserved skeleton of its kind to date.<ref name=BigAlTwo/> The completeness, preservation, and scientific importance of this skeleton gave "Big Al" its name; the individual itself was below the average size for ''Allosaurus fragilis'',<ref name=BBbigal/> and was a subadult estimated at only 87%&nbsp;grown.<ref name=RRH02>{{cite journal |last=Hanna |first=Rebecca R. |year=2002 |title=Multiple injury and infection in a sub-adult theropod dinosaur (''Allosaurus fragilis'') with comparisons to allosaur pathology in the Cleveland-Lloyd dinosaur quarry collection |journal=Journal of Vertebrate Paleontology |volume=22 |issue=1 |pages=76–90 |doi=10.1671/0272-4634(2002)022[0076:MIAIIA]2.0.CO;2}}</ref> The specimen was described by Breithaupt in 1996.<ref name=BB96/> Nineteen of its bones were broken or showed signs of [[infection]], which may have contributed to "Big Al"'s death. [[Pathology|Pathologic]] bones included five ribs, five vertebrae, and four bones of the feet; several damaged bones showed [[osteomyelitis]], a bone infection. A particular problem for the living animal was infection and trauma to the right foot that probably affected movement and may have also predisposed the other foot to injury because of a change in gait.<ref name=RRH02/> ==Species and taxonomy== {{main article|Species of Allosaurus}} It is unclear how many species of ''Allosaurus'' there were. Seven species have been considered potentially valid since 1988 (''A. amplexus'',<ref name=GSP88/> ''A. atrox'',<ref name=GSP88/> ''A. europaeus'',<ref name=OMetal06/> the [[type species]] ''A. fragilis'',<ref name=HMC04/> the as-yet not formally described "A. jimmadseni",<ref name=DJC00/> ''A. maximus'',<ref name=DKS98/> and ''A. tendagurensis''<ref name=HMC04/>), although only a fraction are usually considered valid at any given time. Additionally, there are 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 [[tetanurae|tetanuran]] theropods, only ''A. fragilis'' (including ''A. amplexus'' and ''A. atrox'' as synonyms), "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''.<ref name=HMC04/> ''A. amplexus'', ''A. atrox'', ''A. fragilis'', "A. jimmadseni", and ''A. maximus'' are all known from remains discovered 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. ''A. fragilis'' is regarded as the most common, known from the remains of at least sixty individuals.<ref name=HMC04/> Debate has gone on since the 1980s regarding the possibility that there are two common Morrison Formation species of ''Allosaurus'', with the second known as ''A. atrox'';<ref name=GSP88/><ref name=LG93>{{cite book |last=Lessem |first=Don |coauthors=and Glut, Donald F. |year=1993 |title=The Dinosaur Society's Dinosaur Encyclopedia |chapter=''Allosaurus'' |pages=19–20|publisher=Random House|isbn=0-679-41770-2}}</ref> recent work has followed a "one species" interpretation,<ref name=HMC04/> with the differences seen in the Morrison Formation material attributed to individual variation.<ref name=DKS96>{{cite journal |last=Smith |first=David K. |year=1996 |title=A discriminant analysis of ''Allosaurus'' population using quarries as the operational units |journal=Museum of Northern Arizona Bulletin |volume=60 |pages=69–72}}</ref><ref name=DKS99>{{cite journal |last=Smith |first=David K. |year=1999 |title=Patterns of size-related variation within ''Allosaurus'' |journal=Journal of Vertebrate Paleontology |volume=19 |issue=2 |pages=402–403}}</ref> ''A. europaeus'' was found in the Kimmeridgian-age Porto Novo Member of the [[Lourinhã Formation]],<ref name=OMetal06>{{cite book |last=Mateus |first=Octávio |coauthors=Walen, Aart; and Antunes, Miguel Telles |year=2006 |chapter=The large theropod fauna of the Lourinha Formation (Portugal) and its similarity to that of the Morrison Formation, with a description of a new species of ''Allosaurus'' |editor=Foster, John R.; and Lucas, Spencer G. (eds.) |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |series=New Mexico Museum of Natural History and Science Bulletin, '''36''' |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque, New Mexico |pages=123–129}}</ref> but may be the same as ''A. fragilis''.<ref name=MDOE07>{{cite journal |last=Malafaia |first=Elisabete |coauthors=Dantas, Pedro; Ortega, Francisco; and Escaso, Fernando |year=2007 |title=Nuevos restos de Allosaurus fragilis (Theropoda: Carnosauria) del yacimiento de Andrés (Jurásico Superior; centro-oeste de Portugal) |journal=Cantera Paleontológica |pages=255–271 |language=Spanish with English abstract |url=http://www.dfmf.uned.es/~fortega/uned_fo_pdf/2007_Malafaia_etal_EJIP07.pdf |format=pdf }}</ref> ''A. tendagurensis'' was found in Kimmeridgian-age rocks of [[Tendaguru]], in [[Mtwara Region|Mtwara]], Tanzania.<ref name=WJ25>{{cite journal |last=Janensch |first=Werner |year=1925 |title=Die Coelurosaurier und Theropoden der Tendaguru-Schichten Deutsch-Ostafrikas |journal=Palaeontographica, Supplement 7 |volume=1 |pages=1–99 |language=German}}</ref> Although the most recent review tentatively accepted it as a valid species of ''Allosaurus'', it may be a more basal tetanuran,<ref name=OWMR05>{{cite journal |last=Rauhut |first=Oliver W.M. |year=2005 |title=Post-cranial remains of 'coelurosaurs' (Dinosauria, Theropoda) from the Late Jurassic of Tanzania |journal=Geological Magazine |volume=142 |issue=1 |pages=97–107 |doi=10.1017/S0016756804000330 }}</ref> or simply a [[nomen dubium|dubious]] theropod.<ref name=DFG97/> Although obscure, it was a large theropod, possibly around 10&nbsp;meters long (33&nbsp;ft) and 2.5&nbsp;metric tons (2.8&nbsp;short tons) in weight.<ref name=MMDML03/> ''Allosaurus'' is regarded as a probable synonym of the genera ''Antrodemus'', ''Creosaurus'', ''Epanterias'', and ''Labrosaurus''.<ref name=HMC04/> Most of the species that are regarded as synonyms of ''A. fragilis'', or that were misassigned to the genus, are obscure and were based on scrappy remains. One exception is ''Labrosaurus ferox'', 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.<ref name=OCM84>{{cite journal |last=Marsh |first=Othniel Charles |year=1884 |title=Principal characters of American Jurassic dinosaurs. Part VIII |journal=American Journal of Science, Series 3 |volume=27 |pages=329–340}}</ref> Later researchers suggested that the bone was [[pathology|pathologic]], showing an injury to the living animal,<ref name=CWG20/> and that part of the unusual form of the rear of the bone was due to plaster reconstruction.<ref name=MW00>{{cite book |last=Madsen |first=James H. |coauthors=and Welles, Samuel P. |title=''Ceratosaurus'' (Dinosauria, Theropoda), a Revised Osteology |series=Miscellaneous Publication, '''00-2''' |publisher=Utah Geological Survey |isbn=1-55791-380-3}}</ref> It is now regarded as an example of ''A. fragilis.''<ref name=HMC04/> Other remains thought to pertain to ''Allosaurus'' have come from across the world, including [[Australia]],<ref name=MFR81>{{cite journal |last=Molnar |first=Ralph E. |coauthors=Flannery, Timothy F.; and Rich, Thomas H.V. |year=1981 |title=An allosaurid theropod dinosaur from the Early Cretaceous of Victoria, Australia |journal=Alcheringa |volume=5 |pages=141–146 }}</ref> [[Siberia]],<ref name=ANNR14>{{cite journal |last=Riabinin |first=Anatoly Nikolaenvich |year=1914 |title=Zamtka o dinozavry ise Zabaykalya |journal=Trudy Geologichyeskago Muszeyah Imeni Petra Velikago Imperatorskoy Academiy Nauk |volume=8 |issue=5 |pages=133–140 |language=Russian}}</ref> and [[Switzerland]],<ref name=DFG97/> but these fossils have been reassessed as belonging to other dinosaurs. == Paleoecology == [[Image:Alloquarrynolang.png|thumb|left|Locations in the Morrison Formation (yellow) where ''Allosaurus'' remains have been found.]] ''Allosaurus'' was the most common large theropod in the vast tract of [[American West|Western American]] fossil-bearing rock known as the Morrison Formation, accounting for 70 to 75% of theropod specimens,<ref name=JF07/> and as such was at the top [[trophic level]] of the Morrison [[food chain|food web]].<ref name=JRF03a>{{cite book |last=Foster |first=John R. |title=Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. |year=2003 |series=New Mexico Museum of Natural History and Science Bulletin, '''23''' |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque, New Mexico |pages=29}}</ref> The Morrison Formation is interpreted as a [[semiarid]] environment with distinct [[wet season|wet]] and [[dry season]]s, and flat [[floodplain]]s.<ref name=DAR89>{{cite book |last=Russell |first=Dale A. |authorlink=Dale Russell |title=An Odyssey in Time: Dinosaurs of North America |year=1989 |publisher=NorthWord Press |location=Minocqua, Wisconsin |isbn=1-55971-038-1 |pages=175–176 }}</ref> Vegetation varied from [[river]]-lining forests of [[conifer]]s, [[tree fern]]s, and [[fern]]s, to fern [[savanna]]s with rare trees.<ref name=KC06>{{cite book |last=Carpenter |first=Kenneth |authorlink=Kenneth Carpenter |year=2006 |chapter=Biggest of the big: a critical re-evaluation of the mega-sauropod ''Amphicoelias fragillimus'' |editors=Foster, John R.; and Lucas, Spencer G. (eds.) |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |series=New Mexico Museum of Natural History and Science Bulletin, '''36''' |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque, New Mexico |pages=131–138 |url=https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/Amphicoelias.pdf |format=pdf}}</ref> The Morrison Formation has been a rich fossil hunting ground, holding fossils of [[chlorophyta|green alage]], [[fungi]], [[moss]]es, [[equisetum|horsetails]], ferns, [[cycad]]s, [[ginkgo]]es, and several families of [[conifer]]s. Other fossils discovered include [[bivalve]]s, [[snail]]s, [[actinopterygii|ray-finned fishes]], [[frog]]s, [[salamander]]s, [[turtle]]s, [[sphenodontia|sphenodonts]], [[lizard]]s, terrestrial and aquatic [[crocodylomorpha]]ns, several species of [[pterosaur]], numerous dinosaur species, and early [[mammal]]s such as [[docodonta|docodonts]], [[multituberculata|multituberculates]], [[symmetrodonta|symmetrodonts]], and [[triconodonta|triconodonts]]. Such dinosaurs as the theropods ''Ceratosaurus'', ''[[Ornitholestes]]'', and ''[[Torvosaurus]]'', the [[sauropod]]s ''[[Apatosaurus]]'', ''[[Brachiosaurus]]'', ''[[Camarasaurus]]'', and ''[[Diplodocus]]'', and the [[ornithischia]]ns ''[[Camptosaurus]]'', ''[[Dryosaurus]]'', and ''[[Stegosaurus]]'' are known from the Morrison.<ref name=DJCetal06>{{cite book |last=Chure |first=Daniel J. |coauthors=Litwin, Ron; Hasiotis, Stephen T.; Evanoff, Emmett; and Carpenter, Kenneth |year=2006 |chapter=The fauna and flora of the Morrison Formation: 2006 |editor=Foster, John R.; and Lucas, Spencer G. (eds.) |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |series=New Mexico Museum of Natural History and Science Bulletin, '''36''' |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque, New Mexico |pages=233–248}}</ref> The Late Jurassic formations of Portugal where ''Allosaurus'' is present are interpreted as having been similar to the Morrison but with a stronger [[ocean|marine]] influence. Many of the dinosaurs of the Morrison Formation are the same genera as those seen in Portuguese rocks (mainly ''Allosaurus'', ''Ceratosaurus'', ''Torvosaurus'', and ''Apatosaurus''), or have a close counterpart (''Brachiosaurus'' and ''[[Lusotitan]]'', ''Camptosaurus'' and ''[[Draconyx]]'').<ref name=OM06>{{cite book |last=Mateus |first=Octávio |year=2006 |chapter=Jurassic dinosaurs from the Morrison Formation (USA), the Lourinhã and Alcobaça Formations (Portugal), and the Tendaguru Beds (Tanzania): A comparison |editor=Foster, John R.; and Lucas, Spencer G. (eds.) |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |series=New Mexico Museum of Natural History and Science Bulletin, '''36''' |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque, New Mexico |pages=223–231}}</ref> [[Image:BrushyBasin.JPG|thumb|Outcrop of the Brushy Basin Member of the Morrison Formation, west of Green River, Utah, on the [[Colorado Plateau]].]] ''Allosaurus'' coexisted with fellow large theropods ''Ceratosaurus'' and ''Torvosaurus'' in both the United States and Portugal,<ref name=OM06/> The three appear to have had different [[ecological niche]]s, based on anatomy and the location of fossils. Ceratosaurs and torvosaurs may have preferred to be active around waterways, and had lower, thinner bodies that would have given them an advantage in forest and underbrush terrains, whereas allosaurs were more compact, with longer legs, faster but less maneuverable, and seem to have preferred dry floodplains.<ref name=BB04>{{cite book |last=Bakker |first=Robert T. |coauthors=and Bir, Gary |year=2004 |chapter=Dinosaur crime scene investigations: theropod behavior at Como Bluff, Wyoming, and the evolution of birdness |editor=Currie, Philip J.; Koppelhus, Eva B.; Shugar, Martin A.; and Wright, Joanna L. (eds.) |title=Feathered Dragons: Studies on the Transition from Dinosaurs to Birds |publisher=Indiana University Press |location=Bloomington and Indianapolis |pages=301–342 |isbn=0-253-34373-9}}</ref> ''Ceratosaurus'', better known than ''Torvosaurus'', differed noticeably from ''Allosaurus'' in functional anatomy by having a taller, narrower skull with large, broad teeth.<ref name=DH98/><!--if anyone finds the ref where ''Allosaurus'' was suggested as a female ''Ceratosaurus'', here's a good place to put it for irony--> ''Allosaurus'' was itself a potential food item to other carnivores, as illustrated by an ''Allosaurus'' [[pubis (bone)|pubic foot]] marked by the teeth of another theropod, probably ''Ceratosaurus'' or ''Torvosaurus''. The location of the bone in the body (along the bottom margin of the torso and partially shielded by the legs), and the fact that it was among the most massive in the skeleton, indicates that the ''Allosaurus'' was being scavenged.<ref name=CFJ98>{{cite journal |last=Chure |first=Daniel J. |coauthors=Fiorillo, Anthony R.; and Jacobsen, Aase |year=2000 |title=Prey bone utilization by predatory dinosaurs in the Late Jurassic of North America, with comments on prey bone use by dinosaurs throughout the Mesozoic |journal=Gaia |volume=15 |issue= |pages=227–232 |issn=0871-5424| url=http://www.mnhn.ul.pt/geologia/gaia/17.pdf |format=pdf}}</ref> ==Paleobiology== ===Life history=== The wealth of ''Allosaurus'' fossils, from nearly all ages of individuals, allows scientists to study how the animal grew and how long its lifespan may have been. Remains may reach as far back in the lifespan as [[egg (biology)|eggs]]—crushed eggs from Colorado have been suggested as those of ''Allosaurus''.<ref name=DFG97/> Based on [[Histology|histological]] analysis of limb bones, the upper age limit for ''Allosaurus'' is estimated at 22 to 28&nbsp;years, which is comparable to that of other large theropods like ''[[Tyrannosaurus]]''. From the same analysis, its maximum growth appears to have been at age&nbsp;15, with an estimated growth rate of about 150&nbsp;kilograms (330&nbsp;[[pound (mass)|lb]]) per year.<ref name=PBetal06/> Medullary bone tissue, also found in dinosaurs as diverse as ''[[Tyrannosaurus]]'' and ''[[Tenontosaurus]]'', has been found in at least one ''Allosaurus'' specimen, a [[tibia|shin bone]] from the Cleveland-Lloyd Quarry. Today, this bone tissue is only formed in female birds that are laying eggs, as it is used to supply [[calcium]] to shells. Its presence in the ''Allosaurus'' individual establishes sex and shows she had reached reproductive age. By counting growth lines, it was shown that she was 10&nbsp;years old at death, so sexual maturity in ''Allosaurus'' was attained well before maximum growth and size.<ref name=LW08>{{cite journal |last=Lee |first=Andrew H. |coauthors=and Werning, Sarah |year=2008 |title=Sexual maturity in growing dinosaurs does not fit reptilian growth models |journal=Proceedings of the National Academy of Sciences |volume=105 |issue=2 |pages=582–587 |doi=10.1073/pnas.0708903105 |pmid=18195356}}</ref> The discovery of a juvenile specimen with a nearly complete hindlimb shows that the legs were relatively longer in juveniles, and the lower segments of the leg (shin and foot) were relatively longer than the thigh. These differences suggest that younger ''Allosaurus'' were faster and had different hunting strategies than adults, perhaps chasing small prey as juveniles, then becoming ambush hunters of large prey upon adulthood.<ref name=FC06/> The thigh bone became thicker and wider during growth, and the cross-section less circular, as muscle attachments shifted, muscles became shorter, and the growth of the leg slowed. These changes imply that juvenile legs has less predictable stresses compared with adults, which would have moved with more regular forward progression.<ref name=LCS02>{{cite journal |last=Loewen |first=Mark A. |coauthors=Carrano, Matthew T.; and Sampson, Scott D. |year=2002 |title=Ontogenetic changes in hindlimb musculature and function in the Late Jurassic theropod ''Allosaurus'' |journal=Journal of Vertebrate Paleontology |volume=22 |issue=3, Suppl. |pages=80A }}</ref> ===Feeding=== [[Image:Allosaurus Jaws Steveoc86.jpg|thumb|''Allosaurus'' attacking, based on the theories of Bakker (1998) and Rayfield ''et al.'' (2001).]] Paleontologists accept ''Allosaurus'' as an active predator of large animals. [[Sauropod]]s seem to be likely candidates as both live prey and as objects of [[scavenging]], based on the presence of scrapings on sauropod bones fitting allosaur teeth well and the presence of shed allosaur teeth with sauropod bones.<ref name=FS04>Fastovsky, David E.; and Smith, Joshua B. (2004). "Dinosaur Paleoecology", in ''The Dinosauria'' (2nd). 614–626.</ref> There is dramatic evidence for allosaur attacks on ''Stegosaurus'', including an ''Allosaurus'' tail vertebra with a partially healed puncture wound that fits a ''Stegosaurus'' [[thagomizer|tail spike]], and a ''Stegosaurus'' neck plate with a U-shaped wound that correlates well with an ''Allosaurus'' snout.<ref name=KSMW05>{{cite book |first=Carpenter |last=Kenneth |coauthors=Sanders, Frank; McWhinney, Lorrie A.; and Wood, Lowell |title=The Carnivorous Dinosaurs|year=2005 |chapter=Evidence for predator-prey relationships: Examples for ''Allosaurus'' and ''Stegosaurus'' |editor=Carpenter, Kenneth (ed.)|pages=325&ndash;350 |publisher=Indiana University Press |location=Bloomington and Indianapolis |isbn= 0-253-34539-1 |url=https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/allo-stego.pdf |format=pdf}}</ref> However, as Gregory Paul noted in 1988, ''Allosaurus'' was probably not a predator of fully grown sauropods, unless it hunted in packs, as it had a modestly sized skull and relatively small teeth, and was greatly outweighed by contemporaneous sauropods.<ref name=GSP88/> Another possibility is that it preferred to hunt juveniles instead of fully grown adults.<ref name=LG93/><ref name=JF07/> Research in the 1990s and 2000s may have found other solutions to this question. [[Robert T. Bakker]], comparing ''Allosaurus'' to [[Cenozoic]] sabre-toothed carnivorous mammals, found similar adaptations, such as a reduction of jaw muscles and increase in neck muscles, and the ability to open the jaws extremely wide. Although ''Allosaurus'' did not have sabre teeth, Bakker suggested another mode of attack that would have used such neck and jaw adaptations: the short teeth in effect became small serrations on a [[saw]]-like cutting edge running the length of the upper jaw, which would have been driven into prey. This type of jaw would permit slashing attacks against much larger prey, with the goal of weakening the victim.<ref name=BB98/> [[Image:ROM dinosaurs.jpg|thumb|left|''Allosaurus'' and ''Stegosaurus'' skeletons, Denver Museum of Science and Nature]] Similar conclusions were drawn by another study using [[finite element analysis]] on an ''Allosaurus'' skull. According to their biomechanical analysis, the skull was very strong but had a relatively small bite force. By using jaw muscles only, it could produce a bite force of 805 to 2,148&nbsp;[[Newton|N]], less than the values for [[alligator]]s (13,000&nbsp;N), [[lion]]s (4,167&nbsp;N), and [[leopard]]s (2,268&nbsp;N), but the skull could withstand nearly 55,500&nbsp;N of vertical force against the tooth row. The authors suggested that ''Allosaurus'' used its skull like a hatchet against prey, attacking open-mouthed, slashing flesh with its teeth, and tearing it away without splintering bones, unlike ''Tyrannosaurus'', which is thought to have been capable of damaging bones. They also suggested that the architecture of the skull could have permitted the use of different strategies against different prey; the skull was light enough to allow attacks on smaller and more agile ornithopods, but strong enough for high-impact ambush attacks against larger prey like stegosaurids and sauropods.<ref name=ERetal01/> Their interpretations were challenged by other researchers, who found no modern analogues to a hatchet attack and considered it more likely that the skull was strong to compensate for its open construction when absorbing the stresses from struggling prey.<ref name=FK02>{{cite journal |last=Frazzetta |first=T.H. |coauthors=and Kardong, Kenneth V. |year=2002 |title=Prey attack by a large theropod dinosaur |journal=Nature |volume=416 |pages=387–388 |doi=10.1038/416387a}}</ref> The original authors noted that ''Allosaurus'' itself has no modern equivalent, that the tooth row is well-suited to such an attack, and that articulations in the skull cited by their detractors as problematic actually helped protect the [[palate]] and lessen stress.<ref name=ERetal02>{{cite journal |last=Rayfield |first=Emily J. |coauthors=Norman, David B.; and Upchurch, Paul |year=2002 |title=Prey attack by a large theropod dinosaur: Response to Frazzetta and Kardong, 2002 |journal=Nature |volume=416 |pages=388 |doi=10.1038/416388a}}</ref> Another possibility for handling large prey is that theropods like ''Allosaurus'' were "flesh grazers" which could take bites of flesh out of living sauropods that were sufficient to sustain the predator so it would not have needed to expend the effort to kill the prey outright. This strategy would also potentially have allowed the prey to recover and be fed upon in a similar way later.<ref name=HMC04/> An additional suggestion notes that ornithopods were the most common available dinosaurian prey, and that allosaurs may have subdued them by using an attack similar to that of modern big cats: grasping the prey with their forelimbs, and then making multiple bites on the throat to crush the trachea.<ref name=JF07/> This is compatible with other evidence that the forelimbs were strong and capable of restraining prey.<ref name=KC02>{{cite journal |last=Carpenter |first=Kenneth |year=2002 |title=Forelimb biomechanics of nonavian theropod dinosaurs in predation |journal=Senckebergiana lethaea |volume=82 |issue=1 |pages=59–76| url=https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/theropod%20forelimb.pdf |format=pdf}}</ref> Other aspects of feeding include the eyes, arms, and legs. The shape of the skull of ''Allosaurus'' limited potential [[binocular vision]] to 20° of width, slightly less than that of modern [[crocodilia]]ns. As with crocodilians, this may have been enough to judge prey distance and time attacks.<ref name=KAS06>{{cite journal |last=Stevens |first=Kent A. |year=2006 |title=Binocular vision in theropod dinosaurs |journal=Journal of Vertebrate Paleontology |volume=26 |issue=2 |pages=321–330 |doi=10.1671/0272-4634(2006)26[321:BVITD]2.0.CO;2 }}</ref> The arms, compared with those of other theropods, were suited for both grasping prey at a distance or clutching it close,<ref name=KC02/> and the articulation of the claws suggests that they could have been used to hook things.<ref name=CWG20/> Finally, the top speed of ''Allosaurus'' has been estimated at 30 to 55&nbsp;kilometers per hour (19 to 34&nbsp;miles per hour).<ref name=PC98>{{cite journal |last=Christiansen |first=Per |year=1998 |title=Strength indicator values of theropod long bones, with comments on limb proportions and cursorial potential |journal=Gaia |volume=15 |issue= |pages=241–255 |url=http://www.mnhn.ul.pt/geologia/gaia/19.pdf |issn=0871-5424 |format=pdf}}</ref> ===Social behavior=== ''Allosaurus'' has long been regarded in the semitechnical and popular literature as an animal that preyed on sauropods and other large dinosaurs by hunting in groups.<ref name=DL83/><ref name=DBN85/><ref name=LG93/> Robert T. Bakker has extended social behavior to parental care, and has interpreted shed allosaur teeth and chewed bones of large prey animals as evidence that adult allosaurs brought food to [[lair]]s for their young to eat until they were grown, and prevented other carnivores from scavenging on the food.<ref name=RTB97/> However, there is actually little evidence of gregarious behavior in theropods,<ref name=HMC04/> and social interactions with members of the same species would have included antagonistic encounters, as shown by injuries to gastralia<ref name=DJC00b/> and bite wounds to skulls (the pathologic lower jaw named ''Labrosaurus ferox'' is one such possible example). Such head-biting may have been a way to establish dominance in a [[pack hunter|pack]] or to settle [[territory (animal)|territorial]] disputes.<ref name=TC98>{{cite journal |last=Tanke |first=Darren H. |authorlink=Darren Tanke |coauthors=and Currie, Philip J. |year=1998 |title=Head-biting behavior in theropod dinosaurs: paleopathological evidence |journal=Gaia |issue=15 |pages=167–184 |url=http://www.mnhn.ul.pt/geologia/gaia/12.pdf |issn=0871-5424 |format=pdf}}</ref> Although ''Allosaurus'' may have hunted in packs,<ref name=completedino>{{cite book |title=The Complete Dinosaur |url=http://books.google.com/books?id=FOViD-lDPy0C&pg=PA228&dq=Allosaurus+behavior&sig=Qn8lXqq4zQVAt2wB8_yjEalRffI |last=Currie |first=Philip J. |chapter=Theropods |editor=Farlow, James; and Brett-Surman, M.K. (eds.) |year=1999 |publisher=Indiana University Press |location=Indiana |isbn=0253213134 |pages=p. 228 }}</ref> recent research suggests that ''Allosaurus'' and other theropods were like other [[diapsid]]s and had largely aggressive instead of cooperative interactions with other members of their own species. One study noted cooperative hunting of prey much larger than an individual predator, as is commonly inferred for theropod dinosaurs, is rare among [[vertebrate]]s in general, and modern [[diapsida|diapsids]] (including lizards, crocodiles, and birds) very rarely cooperate to hunt in such a way. Many modern diapsid predators are territorial and will kill and [[cannibalism (zoology)|cannibalize]] intruders of the same species, and will also do the same to smaller individuals that attempt to eat before them when aggregated at feeding sites. This suggests that, for example, the Cleveland-Lloyd quarry shows ''Allosaurus'' individuals were drawn together to feed on other disabled or dead allosaurs, and sometimes were killed in the process, thus accumulating. This could explain the high proportion of juvenile and subadult allosaurs present, as juveniles and subadults are disproportionally killed at modern group feeding sites of animals like [[crocodile]]s and [[komodo dragon]]s. The same interpretation applies to Bakker's lair sites.<ref name=RB07>{{cite journal|last=Roach|first=Brian T.|coauthors=and Brinkman, Daniel L. |year=2007 |title=A reevaluation of cooperative pack hunting and gregariousness in ''Deinonychus antirrhopus'' and other nonavian theropod dinosaurs|journal=Bulletin of the Peabody Museum of Natural History |volume=48 |issue=1 |pages=103–138 |doi=10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2}}</ref> There is some evidence for cannibalism in ''Allosaurus'', including ''Allosaurus'' shed teeth found among rib fragments, possible tooth marks on a [[scapula|shoulder blade]],<ref name=BGD04>{{cite journal |last=Goodchild Drake |first=Brandon |year=2004 |title=A new specimen of ''Allosaurus'' from north-central Wyoming |journal=Journal of Vertebrate Paleontology |volume=24 |issue=3, Suppl. |pages=65A }}</ref> and cannibalized allosaur skeletons among the bones at Bakker's lair sites.<ref name=BB04/> ===Brain and senses=== The brain of ''Allosaurus'', as interpreted from spiral [[computed tomography|CT scanning]] of an [[endocranial cast|endocast]], was more consistent with [[crocodilia]]n brains than those of the other living [[archosaur]]s, birds. The structure of the [[vestibular system|vestibular apparatus]] indicates that the skull was held nearly horizontal, as opposed to strongly tipped up or down. The structure of the [[inner ear]] was like that of a crocodilian, and so ''Allosaurus'' probably could have heard lower frequencies best, and would have had trouble with subtle sounds. The [[olfactory bulb]]s were large and seem to have been well suited for detecting odors, although the area for evaluating smells was relatively small.<ref name=SWR99/> ==In popular culture== [[Image:Allosaurus in Baltow 20060916 1500.jpg|thumb|right|''Allosaurus'' model in [[Poland]].]] Along with ''Tyrannosaurus'', ''Allosaurus'' has come to represent the quintessential large, carnivorous dinosaur in popular culture. It is a common dinosaur in museums, due in particular to the excavations at the Cleveland Lloyd Dinosaur Quarry; by 1976, as a result of cooperative operations, 38 museums in eight countries on three continents had Cleveland-Lloyd allosaur material or casts.<ref name=JM76/> ''Allosaurus'' is the official [[state fossil]] of Utah.<ref name=statefossil>{{cite web |url=http://pioneer.utah.gov/utah_on_the_web/utah_symbols/fossil.html |title=Utah Symbols – State Fossil |accessdate=2007-09-30|publisher=State of Utah }}</ref> ''Allosaurus'' has been depicted in popular culture since the early years of the 20th century. It is top predator in both [[Arthur Conan Doyle]]'s 1912 novel, ''[[The Lost World (Arthur Conan Doyle)|The Lost World]]'', and the [[The Lost World (1925 film)|1925 film adaptation]], the first full-length motion picture to feature dinosaurs (it is not to be confused with ''Tyrannosaurus'', which also appears in the film).<ref name=GBS97>{{cite book |last=Glut |first=Donald F. |coauthors= Brett-Surman, Michael K.|year=1997 |editor=Farlow, James; and Brett-Surman, Michael K. (eds.) |chapter=Dinosaurs and the media |title=The Complete Dinosaur |publisher=Indiana University Press |location=Bloomington and Indianapolis |pages=675–706 |isbn=0-253-33349-0}}</ref> It later became the starring dinosaur of the 1956 film ''[[The Beast of Hollow Mountain]]'',<ref name=DL90>Lambert, ''Dinosaur Data Book'', p. 299.</ref> and the 1969 film ''[[The Valley of Gwangi]]'', two [[genre]] combinations of living dinosaurs with [[Western (genre)|Westerns]]. In ''The Valley of Gwangi'', Gwangi is billed as an ''Allosaurus'', although [[Ray Harryhausen]] based his model for the creature on Charles R. Knight's depiction of a ''Tyrannosaurus''. Harryhausen sometimes confuses the two, stating in a DVD interview "They're both meat eaters, they're both tyrants... one was just a bit larger than the other."<ref>''Return to the Valley'', a documentary on the Region 1 ''Valley of Gwangi'' DVD.</ref> In nonfictional presentations, ''Allosaurus'' appears in the second and fifth episodes of the [[BBC]] television series ''[[Walking with Dinosaurs]]'', and the ''Walking with Dinosaurs'' special ''[[The Ballad of Big Al]]'' chronicles the life of the ''Allosaurus'' specimen nicknamed "Big Al". ==References== {{reflist|colwidth=35em}} ==External links== {{portalpar|Dinosaurs}} {{Commons|Allosaurus}} {{Wikibooks|Wikijunior Dinosaurs/Allosaurus}} * [http://www.uwyo.edu/GeoMuseum/tour/allosaurus.asp ''Allosaurus'', the story of "Big Al"], from the University of Wyoming Geological Museum in Laramie. * [http://web.archive.org/web/20060716101519/http://students.washington.edu/eoraptor/Carnosauria.htm#Allosaurusfragilis Specimens, discussion, and references pertaining to ''Allosaurus''] at The Theropod Database. * [http://www.dinodata.org/index.php?option=com_content&task=view&id=6029&Itemid=67 ''Allosaurus''] at DinoData. * [http://pioneer.utah.gov/utah_on_the_web/utah_symbols/fossil.html Public Pioneer, Utah State Fossil, ''Allosaurus''], from Utah.gov. * [http://skeletaldrawing.com/psgallery/images/allosaurus.jpg Restoration of MOR 693 ("Big Al")] and [http://skeletaldrawing.com/psgallery/pages/allosaurdeepmuscle.html and muscle and organ restoration] at Scott Hartman's Skeletal Drawing website. * [http://dml.cmnh.org/1995Nov/msg00278.html List of the many possible ''Allosaurus'' species...] {{Featured article}} [[Category:Carnosaurs]] [[Category:Dinosaurs of Europe]] [[Category:Jurassic dinosaurs]] [[Category:Dinosaurs of North America]] [[Category:Symbols of Utah]] [[Category:Morrison fauna]] [[ar:ألوصور]] [[bg:Алозаври]] [[ca:Al·losaure]] [[cs:Allosaurus]] [[da:Allosaurus]] [[de:Allosaurus]] [[el:Αλλόσαυρος]] [[es:Allosaurus]] [[eo:Alosaŭro]] [[fr:Allosaurus]] [[hr:Alosaur]] [[it:Allosaurus]] [[he:אלוזאור]] [[la:Allosaurus]] [[lv:Allozaurs]] [[lt:Alozauras]] [[hu:Allosaurus]] [[ms:Allosaurus]] [[nl:Allosaurus]] [[ja:アロサウルス]] [[no:Allosaurus]] [[pl:Allozaur]] [[pt:Alossauro]] [[ro:Allosaurus]] [[ru:Аллозавр]] [[simple:Allosaurus]] [[sk:Allosaurus]] [[sr:Алосаур]] [[fi:Allosaurus]] [[sv:Allosaurus]] [[vi:Allosaurus]] [[tr:Allosaurus]] [[zh:異特龍]]