fbpx
Wikipedia

Allosaurus

June 27, 2023

Allosaurus (/ˌæləˈsɔːrəs/)[2][3] is an extinct genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period (Kimmeridgian to late Tithonian ages). The name "Allosaurus" means "different lizard", alluding to its unique (at the time of its discovery) concave vertebrae. It is derived from the Greek words ἄλλος (allos) ("different", "strange", or "other") and σαῦρος (sauros) ("lizard" or "reptile"). The first fossil remains that could definitively be ascribed to this genus were described in 1877 by famed paleontologist Othniel Charles Marsh. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles.

Allosaurus
Temporal range: Late Jurassic (Kimmeridgian to Tithonian), 155–145 Ma
A. jimmadseni specimen "Big Al II" (SMA 0005)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: †Allosauridae
Subfamily: †Allosaurinae
Marsh, 1878
Genus: †Allosaurus
Marsh, 1877
Type species
†Allosaurus fragilis
Marsh, 1877
Other species[1]
Synonyms
List

Allosaurus was a large bipedal predator for its time. Its skull was light, robust, and equipped with dozens of sharp, serrated teeth. It averaged 8.5 meters (28 ft) in length for A. fragilis, with the largest specimens estimated as being 9.7 metres (32 ft) long. Relative to the large and powerful legs, its three-fingered hands were small and the body was balanced by a long, muscular tail. It is classified as an allosaurid, a type of carnosaurian theropod dinosaur.

The genus has a very complicated taxonomy and includes at least three 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 known from Portugal. It was known for over half of the 20th century as Antrodemus, but a study of the abundant 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 most abundant large predator of the Morrison Formation, Allosaurus was at the top of the food chain and probably preyed on contemporaneous large herbivorous dinosaurs, with the possibility of hunting other predators. Potential prey included ornithopods, stegosaurids, and sauropods. Some paleontologists interpret Allosaurus as having had cooperative social behavior and hunting in packs, while others believe individuals may have been aggressive toward each other and that congregations of this genus are the result of lone individuals feeding on the same carcasses.

Discovery and history

Early discoveries and research

 
Mounted A. fragilis specimen (AMNH 5753), posed as scavenging an Apatosaurus
 
AMNH 5753 in a Charles R. Knight life restoration

The discovery and early study of Allosaurus is complicated by the multiplicity of names coined during the Bone Wars of the late 19th century. The first described fossil in this history was a bone obtained secondhand by Ferdinand Vandeveer Hayden in 1869. It came from 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.[4] He later decided it deserved its own genus, Antrodemus.[5]

Allosaurus itself is based on 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 Greek words allos/αλλος, meaning "strange" or "different", and sauros/σαυρος, meaning "lizard" or "reptile".[6] It was named 'different lizard' because its vertebrae were different from those of other dinosaurs known at the time of its discovery.[7][8] 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, north of Cañon City.[7] O. C. Marsh and Edward Drinker Cope, who were in scientific competition with each other, 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[9] and Labrosaurus,[10] as well as Cope's Epanterias.[11]

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 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.[12] 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 it in 1903 (several years after Cope had died), it was found to be one of the most complete theropod specimens then known and the skeleton, now cataloged as AMNH 5753, was put on public view in 1908.[13] This is the well-known mount poised over a partial Apatosaurus skeleton as if scavenging it, illustrated as such in a painting 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.[14]

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.[15] For example, Williston pointed out in 1901 that Marsh had never been able to adequately distinguish Allosaurus from Creosaurus.[16] 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 named Antrodemus by Leidy was indistinguishable from those of Allosaurus and that Antrodemus should be the preferred name because, as the older name, it had priority.[17] Antrodemus became the accepted name for this familiar genus for over 50 years, until James Henry 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.[18] "Antrodemus" has been used informally for convenience when distinguishing between the skull Gilmore restored and the composite skull restored by Madsen.[19]

Cleveland-Lloyd discoveries

 
A. fragilis at the Cleveland-Lloyd Dinosaur Quarry museum, Utah

Although sporadic work at what became known as the Cleveland-Lloyd Dinosaur Quarry in Emery County, Utah, had taken place as early as 1927 and the fossil site itself described by William L. Stokes in 1945,[20] major operations did not begin there until 1960. Under a cooperative effort involving nearly 40 institutions, thousands of bones were recovered between 1960 and 1965, led by James Henry Madsen.[18] 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 A. fragilis have been found there, out of at a minimum 73 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, suggesting numerous mutually exclusive explanations for how it may have formed. Suggestions have ranged from animals getting stuck in a bog, becoming trapped in deep mud, falling victim to drought-induced mortality around a waterhole, and getting trapped in a spring-fed pond or seep.[21] Regardless of the actual cause, the great quantity of well-preserved Allosaurus remains has allowed this genus to be known in great detail, making it among the best-known of all theropods. Skeletal remains from the quarry pertain to individuals of almost all ages and sizes, from less than 1 meter (3.3 feet)[22] to 12 meters (39 feet) long, and the disarticulation is an advantage for describing bones usually found fused.[18] Due to being one of Utah's two fossil quarries where numerous Allosaurus specimens have been discovered, Allosaurus was designated as the state fossil of Utah in 1988.[23]

Recent work: 1980s–present

The period since Madsen's monograph has been marked by a great expansion in studies dealing with topics concerning Allosaurus in life (paleobiological and paleoecological topics). Such studies have covered topics including skeletal variation,[24] growth,[25][26] skull construction,[27] hunting methods,[28] the brain,[29] and the possibility of gregarious living and parental care.[30] Reanalysis of old material (particularly of large 'allosaur' specimens),[31][32] new discoveries in Portugal,[33] and several very complete new specimens[34][35][36] have also contributed to the growing knowledge base.

"Big Al" and "Big Al II"

 
"Big Al" at the Museum of the Rockies

In 1991, "Big Al" (MOR 693), a 95% complete, partially articulated specimen of Allosaurus was discovered, measuring about 8 meters (about 26 ft) long. MOR 693 was excavated near Shell, Wyoming, by a joint Museum of the Rockies and University of Wyoming Geological Museum team.[37] This skeleton was discovered by a Swiss team, led by Kirby Siber. Chure and Loewen in 2020 identified the individual as a representative of the species Allosaurus jimmadseni. In 1996, the same team discovered a second Allosaurus, "Big Al II". This specimen, the best preserved skeleton of its kind to date, is also referred to Allosaurus jimmadseni.[1]

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,[37] as it was a subadult estimated at only 87% grown.[38] The specimen was described by Breithaupt in 1996.[35] Nineteen of its bones were broken or showed signs of serious infection, which may have contributed to "Big Al's" death. Pathologic bones included five ribs, five vertebrae, and four bones of the feet. Several of its damaged bones showed signs of osteomyelitis, a severe 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. "Big Al" had an infection on the first phalanx on the third toe that was afflicted by an involucrum. The infection was long-lived, perhaps up to six months.[38][39] “Big Al II” is also known to have multiple injuries.[40]

Species

 
Diagram comparing skulls of the three recognized species; A. fragilis (A), A. jimmadseni (B), A. europaeus (C)

Six species of Allosaurus have been named: A. amplus,[41] A. atrox,[42] A. europaeus,[43] the type species A. fragilis,[44] A. jimmadseni[1][42] and A. lucasi.[45] Among these, 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.[1] However, A. europaeus does not show any unique characters compared to the North American species, so a reevaluation of its validity is required.[46][47]

A. fragilis is the type species and was named by Marsh in 1877.[7] 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.[44] Details of the humerus (upper arm) of A. fragilis have been used as diagnostic among Morrison theropods,[18] but A. jimmadseni indicates that this is no longer the case at the species level.[42]

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.[1][42][48][49] 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.[22]

A. fragilis, A. jimmadseni, 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.[44] 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.[31][50] 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.[51][52] 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.[53] A. europaeus was found in the Kimmeridgian-age Porto Novo Member of the Lourinhã Formation,[43] but it may be the same as A. fragilis.[46]

Allosaurus material from Portugal was first reported in 1999 on the basis of MHNUL/AND.001, a partial skeleton including a quadrate, vertebrae, ribs, gastralia, chevrons, part of the hips, and legs. This specimen was assigned to A. fragilis,[33] but the subsequent discovery of a partial skull and neck (ML 415) near Lourinhã, in the Kimmeridgian-age Porto Novo Member of the Lourinhã Formation, spurred the naming of the new species as A. europaeus by Octávio Mateus and colleagues. The species appeared earlier in the Jurassic than A. fragilis and differs from other species of Allosaurus in cranial details.[43] However, more material may show it to be A. fragilis, as originally described.[46]

The issue of species and potential synonyms is complicated by the type specimen of Allosaurus fragilis (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) submitted a petition to the ICZN to have the name "A. fragilis" officially transferred to the more complete specimen USNM4734 (as a neotype).[54]

Synonyms

 
Holotype material of Creosaurus atrox

Creosaurus, Epanterias, and Labrosaurus are regarded as junior synonyms of Allosaurus.[44] Most of the species that are regarded as synonyms of A. fragilis, or that were misassigned to the genus, are obscure and based on very 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.[55] Later researchers suggested that the bone was pathologic, showing an injury to the living animal,[17] and that part of the unusual form of the rear of the bone was due to plaster reconstruction.[56] It is now regarded as an example of A. fragilis.[44]

 
Cast of synonym "A. atrox" at the South Australian Museum.

In his 1988 book, Predatory Dinosaurs of the World, the freelance artist & author Gregory S. Paul proposed that A. fragilis had tall pointed horns and a slender build compared to a postulated second species A. atrox, as well as not being a different sex due to rarity.[31] 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 that includes a couple of pieces of the skull, portions of nine tail vertebrae, two hip vertebrae, an ilium, and ankle and foot bones.[9] Although the idea of two common Morrison allosaur species was followed in some semi-technical and popular works,[50] the 2000 thesis on Allosauridae noted that Charles Gilmore mistakenly reconstructed USNM 4734 as having a shorter skull than the specimens referred by Paul to atrox, refuting supposed differences between USNM 4734 and putative A. atrox specimens like DINO 2560, AMNH 600, and AMNH 666.[42]

"Allosaurus agilis", seen in Zittel, 1887, and Osborn, 1912, is a typographical error for A. fragilis.[42] "Allosaurus ferox" is a typographical error by Marsh for A. fragilis in a figure caption for the partial skull YPM 1893[57] and YPM 1893 has been treated as a specimen of A fragilis.[44] Likewise, "Labrosaurus fragilis" is a typographical error by Marsh (1896) for Labrosaurus ferox.[56] "A. whitei" is a nomen nudum coined by Pickering in 1996 for the complete Allosaurus specimens that Paul referred to A. atrox.[42]

"Madsenius" was coined by David Lambert in 1990,[58] being based on remains from Dinosaur National Monument assigned to Allosaurus or Creosaurus (a synonym of Allosaurus), and was to be described by paleontologist Robert Bakker as "Madsenius trux".[59] However, "Madsenius" is now seen as yet another synonym of Allosaurus because Bakker's action was predicated upon the false assumption of USNM 4734 being distinct from long-snouted Allosaurus due to errors in Gilmore's 1920 reconstruction of USNM 4734.[60]

"Wyomingraptor" was informally coined by Bakker for allosaurid remains from the Morrison Formation of the Late Jurassic. The remains unearthed are labeled as Allosaurus and are housed in the Tate Geological Museum. However, there has been no official description of the remains and "Wyomingraptor" has been dismissed as a nomen nudum, with the remains referable to Allosaurus.[61][62][60]

Formerly assigned species and fossils

 
Antrodemus valens holotype tail vertebra (above) compared to the same of Allosaurus (below)

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 Arundel Formation of Maryland,[63] although most of the remains were removed by Richard Swann Lull to the new ornithopod species Dryosaurus grandis, except for a tooth.[64] It was transferred to Antrodemus by Oliver Hay in 1902, but Hay later clarified that this was an inexplicable error on his part.[65][66] Gilmore considered the tooth nondiagnostic but transferred it to Dryptosaurus, as D. medius.[17] The referral was not accepted in the most recent review of basal tetanurans, and Allosaurus medius was simply listed as a dubious species of theropod.[44] It may be closely related to Acrocanthosaurus.[67]

Allosaurus valens is a new combination for Antrodemus valens used by Friedrich von Huene in 1932;[42] Antrodemus valens itself may also pertain to Allosaurus fragilis,[44] as Gilmore suggested in 1920.[17]

A. lucaris, another Marsh name, was given to a partial skeleton in 1878.[9] He later decided it warranted its own genus, Labrosaurus,[10] but this has not been accepted, and A. lucaris is also regarded as another specimen of A. fragilis.[44] Allosaurus lucaris, is known mostly from vertebrae, sharing characters with Allosaurus.[68] 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 undiagnostic, and thus A. lucaris was a nomen dubium.[54]

Allosaurus sibiricus was described in 1914 by A. N. Riabinin on the basis of a bone, later identified as a partial fourth metatarsal, from the Early Cretaceous of Buryatia, Russia.[69] It was transferred to Chilantaisaurus in 1990,[70] but is now considered a nomen dubium indeterminate beyond Theropoda.[71]

Allosaurus meriani was a new combination by George Olshevsky for Megalosaurus meriani Greppin, 1870, based on a tooth from the Late Jurassic of Switzerland.[72][73] However, a recent overview of Ceratosaurus included it in Ceratosaurus sp.[56]

Apatodon mirus, based on a scrap of vertebra Marsh first thought to be a mammalian jaw, has been listed as a synonym of Allosaurus fragilis.[74][75] However, it was considered indeterminate beyond Dinosauria by Chure,[42] and Mickey Mortimer believes that the synonymy of Apatodon with Allosaurus was due to correspondence to Ralph Molnar by John McIntosh, whereby the latter reportedly found a paper saying that Othniel Charles Marsh admitted that the Apatodon holotype was actually an allosaurid dorsal vertebra.[76]

A. amplexus was named by Gregory S. Paul for giant Morrison allosaur remains, and included in his conception Saurophagus maximus (later Saurophaganax).[31] A. amplexus was originally coined by Cope in 1878 as the type species of his new genus Epanterias,[11] and is based on what is now AMNH 5767, parts of three vertebrae, a coracoid, and a metatarsal.[77] Following Paul's work, this species has been accepted as a synonym of A. fragilis.[44] A 2010 study by Paul and Kenneth Carpenter, however, indicates that Epanterias is temporally younger than the A. fragilis type specimen, so it is a separate species at minimum.[78]

A. maximus was a new combination by David K. Smith for Chure's Saurophaganax maximus, a taxon created by Chure in 1995 for giant allosaurid remains from the Morrison of Oklahoma. These remains had been known as Saurophagus, but that name was already in use, leading Chure to propose a substitute.[32] 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.[24] This reassignment was rejected in a review of basal tetanurans.[44]

There are also several species left over from the synonymizations of Creosaurus and Labrosaurus with Allosaurus. Creosaurus potens was named by Lull in 1911 for a vertebra from the Early Cretaceous of Maryland.[64] It is now regarded as a dubious theropod.[44] Labrosaurus stechowi, described in 1920 by Janensch based on isolated Ceratosaurus-like teeth from the Tendaguru beds of Tanzania,[79] was listed by Donald F. Glut as a species of Allosaurus,[75] is now considered a dubious ceratosaurian related to Ceratosaurus.[56][80] L. sulcatus, named by Marsh in 1896 for a Morrison theropod tooth,[57] which like L. stechowi is now regarded as a dubious Ceratosaurus-like ceratosaur.[56][80]

 
A. tendagurensis tibia, Naturkunde Museum Berlin

A. tendagurensis was named in 1925 by Werner Janensch for a partial shin (MB.R.3620) found in the Kimmeridgian-age Tendaguru Formation in Mtwara, Tanzania.[81] Although tabulated as a tentatively valid species of Allosaurus in the second edition of the Dinosauria,[44] subsequent studies place it as indeterminate beyond Tetanurae, either a carcharodontosaurian or megalosaurid.[82][83] 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.[84]

Kurzanov 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 to them).[85] They were reclassified as an indeterminate theropod.[71] Also, reports of Allosaurus in Shanxi, China go back to at least 1982.[86] These were interpreted as Torvosaurus remains in 2012.[71]

An astragalus (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 refugium for animals that had gone extinct elsewhere.[87] This identification was challenged by Samuel Welles, who thought it more resembled that of an ornithomimid,[88] but the original authors defended their identification.[89] With fifteen years of new specimens and research to look at, Daniel Chure reexamined the bone and found that it was not Allosaurus, but could represent an allosauroid.[90] Similarly, Yoichi Azuma and Phil Currie, in their description of Fukuiraptor, noted that the bone closely resembled that of their new genus.[91] This specimen is sometimes referred to as "Allosaurus robustus", an informal museum name.[48] It likely belonged to something similar to Australovenator,[92] although one study considered it to belong to an abelisaur.[93]

Description

 
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, slightly sloping tail, and reduced forelimbs. Allosaurus fragilis, the best-known species, had an average length of 8.5 m (28 ft) and mass of 1.7 metric tons (1.9 short tons),[75][94] with the largest definitive Allosaurus specimen (AMNH 680) estimated at 9.7 meters (32 feet) long,[84] with an estimated weight of 2.3–2.7 metric tons (2.5–3.0 short tons).[84][95] In his 1976 monograph on Allosaurus, James H. Madsen mentioned a range of bone sizes which he interpreted to show a maximum length of 12 to 13 m (39 to 43 ft).[18] As with dinosaurs in general, weight estimates are debatable, and since 1980 have ranged between 1.5 metric tons (1.7 short tons), 1 to 4 metric tons (1.1 to 4.4 short tons), and approximately 1 metric ton (1.1 short tons) for modal adult weight (not maximum).[96] John Foster, a specialist on the Morrison Formation, suggests that 1 metric ton (1.1 short tons) is reasonable for large adults of A. fragilis, but that 700 kg (1,500 lb) is a closer estimate for individuals represented by the average-sized thigh bones he has measured.[97] Using the subadult specimen nicknamed "Big Al", since assigned to the species Allosaurus jimmadseni,[1] researchers using computer modelling arrived at a best estimate of 1.5 metric tons (1.7 short tons) for the individual, but by varying parameters they found a range from approximately 1.4 metric tons (1.5 short tons) to approximately 2 metric tons (2.2 short tons).[98] A. europaeus has been measured up to 7 m (23 ft) in length and 1 metric ton (1.1 short tons) in body mass.[94]

 
A. jimmadseni skeletal reconstruction

Several gigantic specimens have been attributed to Allosaurus, but may in fact belong to other genera. The closely related genus Saurophaganax (OMNH 1708) reached perhaps 10.5 m (34 ft) in length,[94] and its single species has sometimes been included in the genus Allosaurus as Allosaurus maximus, though recent studies support it as a separate genus.[42] Another potential specimen of Allosaurus, once assigned to the genus Epanterias (AMNH 5767), may have measured 12.1 meters (40 feet) in length.[84] 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 Saurophaganax.[99]

David K. Smith, examining Allosaurus fossils by quarry, found that the Cleveland-Lloyd Dinosaur Quarry (Utah) specimens are generally smaller than those from Como Bluff (Wyoming) or Brigham Young University's Dry Mesa Quarry (Colorado), but the shapes of the bones themselves did not vary between the sites.[51] 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 gradational, suggesting individual variation was responsible.[24] 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 astragalus, an ankle bone.[52] Kenneth Carpenter, using 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 horns, and the proposed differentiation of A. jimmadseni based on the shape of the jugal.[53] A study published by Motani et al., in 2020 suggests that Allosaurus was also sexually dimorphic in the width of the femur's head against its length.[100]

Skull

 
A. jimmadseni skull with diagram highlighting individual bones

The skull and teeth of Allosaurus were modestly proportioned for a theropod of its size. Paleontologist Gregory S. Paul gives a length of 845 mm (33.3 in) for a skull belonging to an individual he estimates at 7.9 m (26 ft) long.[31] 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 14 and 17 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 14 and 17 teeth, with an average count of 16. The teeth became shorter, narrower, 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.[18] Its skull was light, robust and equipped with dozens of sharp, serrated teeth.

The skull had a pair of horns above and in front of the eyes. These horns were composed of extensions of the lacrimal bones,[18] and varied in shape and size. There were also lower paired ridges running along the top edges of the nasal bones that led into the horns.[18] The horns were probably covered in a keratin sheath and may have had a variety of functions, including acting as sunshades for the eyes,[18] being used for display, and being used in combat against other members of the same species[31][101] (although they were fragile).[18] There was a ridge along the back of the skull roof for muscle attachment, as is also seen in tyrannosaurids.[31]

Inside the lacrimal bones were depressions that may have held glands, such as salt glands.[12] Within the maxillae were sinuses that were better developed than those of more basal theropods such as Ceratosaurus and Marshosaurus; they may have been related to the sense of smell, perhaps holding something like Jacobson's organs. The roof of the braincase was thin, perhaps to improve thermoregulation for the brain.[18] 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.[102] The braincase and frontals may also have had a joint.[18]

Postcranial skeleton

 
Life restoration of A. fragilis

Allosaurus had nine vertebrae in the neck, 14 in the back, and five in the sacrum supporting the hips.[103] The number of tail vertebrae is unknown and varied with individual size; James Madsen estimated about 50,[18] while Gregory S. Paul considered that to be too many and suggested 45 or less.[31] There were hollow spaces in the neck and anterior back vertebrae.[18] Such spaces, which are also found in modern theropods (that is, the birds), are interpreted as having held air sacs used in respiration.[44] The rib cage was broad, giving it a barrel chest, especially in comparison to less derived theropods like Ceratosaurus.[104] Allosaurus had gastralia (belly ribs), but these are not common findings,[18] and they may have ossified poorly.[31] In one published case, the gastralia show evidence of injury during life.[34] A furcula (wishbone) was also present, but has only been recognized since 1996; in some cases furculae were confused with gastralia.[34][105] The ilium, the main hip bone, was massive, and the 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 characteristic, with females lacking fused bones to make egg-laying easier.[18] This proposal has not attracted further attention, however.

 
Hand and claws of A. fragilis

The forelimbs of Allosaurus were short in comparison to the hindlimbs (only about 35% the length of the hindlimbs in adults)[106] and had three fingers per hand, tipped with large, strongly curved and pointed claws.[18] The arms were powerful,[31] and the forearm was somewhat shorter than the upper arm (1:1.2 ulna/humerus ratio).[17] The wrist had a version of the semilunate carpal[107] also found in more derived theropods like maniraptorans. Of the three fingers, the innermost (or thumb) was the largest,[31] and diverged from the others.[17] The phalangeal formula is 2-3-4-0-0, meaning that the innermost finger (phalange) has two bones, the next has three, and the third finger has four.[108] The legs were not as long or suited for speed as those of tyrannosaurids, and the claws of the toes were less developed and more hoof-like than those of earlier theropods.[31] Each foot had three weight-bearing toes and an inner dewclaw, which Madsen suggested could have been used for grasping in juveniles.[18] There was also what is interpreted as the splint-like remnant of a fifth (outermost) metatarsal, perhaps used as a lever between the Achilles tendon and foot.[109]

Skin

Skin impressions from Allosaurus have been described. One impression, from a juvenile specimen, measures 30 cm² and is associated with the anterior dorsal ribs/pectoral region.[110] The impression show small scales measuring 1–3 mm in diameter. A large skin impression from the "Big Al Two" specimen, associated with the base of the tail, measures 20 cm x 20 cm, and show large scales measuring up to 2 cm in diameter. However it has been noted that these scales are more similar to those of sauropods, and due to the presence of non-theropod remains associated with the tail of "Big Al Two" there is a possibility that this skin impression is not from Allosaurus.[110]

Another Allosaurus fossil feature a skin impression from the mandible, showing scales measuring 1–2 mm in diameter. The same fossil also preserves skin impressions from the ventral side of the neck, showing broad scutes. A small skin impression from an Allosaurus skull has been reported, but never described.[110]

Classification

Allosaurus was an allosaurid, a member of a family of large theropods within the larger group Carnosauria. The family name Allosauridae was created for this genus in 1878 by Othniel Charles Marsh,[9] 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 Gilmore, 1920,[17] von Huene, 1926,[111] Romer, 1956 and 1966,[112][113] Steel, 1970,[114] and Walker, 1964.[115]

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,[116] Acrocanthosaurus, Chilantaisaurus, Compsosuchus, Stokesosaurus, and Szechuanosaurus.[117] Given modern knowledge of theropod diversity and the advent of cladistic study of evolutionary relationships, none of these theropods is now recognized as an allosaurid, although several, like Acrocanthosaurus and Yangchuanosaurus, are members of closely related families.[44]

 
Restored skeleton of Saurophaganax or A. maximus
 
Illustrations showing the skull of A. jimmadseni from the side (A), top (B), and back (C)

Below is a cladogram based on the analysis of Benson et al. in 2010.[118]

Allosauridae is one of four families in Allosauroidea; the other three are Neovenatoridae,[118] Carcharodontosauridae and Sinraptoridae.[44] Allosauridae has at times been proposed as ancestral to the Tyrannosauridae (which would make it paraphyletic), one example being Gregory S. Paul's Predatory Dinosaurs of the World,[119] but this has been rejected, with tyrannosaurids identified as members of a separate branch of theropods, the Coelurosauria.[120] Allosauridae is the smallest of the carnosaur families, with only Saurophaganax and a currently unnamed French allosauroid accepted as possible valid genera besides Allosaurus in the most recent review.[44] Another genus, Epanterias, is a potential valid member, but it and Saurophaganax may turn out to be large examples of Allosaurus.[31] Recent reviews have kept the genus Saurophaganax and included Epanterias with Allosaurus.[96][44]

Paleobiology

Life history

 
Skeletons at different growth stages on display, the Natural History Museum of Utah

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 eggs—crushed eggs from Colorado have been suggested as those of Allosaurus.[75] Based on histological analysis of limb bones, bone deposition appears to stop at around 22 to 28 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 15, with an estimated growth rate of about 150 kilograms (330 lb) per year.[25]

Medullary bone tissue (endosteally derived, ephemeral, mineralization located inside the medulla of the long bones in gravid female birds) has been reported in at least one Allosaurus specimen, a shin bone from the Cleveland-Lloyd Quarry.[121] 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 has been used to establish sex and show it had reached reproductive age. However, other studies have called into question some cases of medullary bone in dinosaurs, including this Allosaurus individual. Data from extant birds suggested that the medullary bone in this Allosaurus individual may have been the result of a bone pathology instead.[122] However, with the confirmation of medullary tissue indicating sex in a specimen of Tyrannosaurus, it may be possible to ascertain whether or not the Allosaurus in question was indeed female.[123]

 
Restoration of a juvenile Allosaurus

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.[26] 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.[124] Conversely, the skull bones appear to have generally grown isometrically, increasing in size without changing in proportion.[53]

Feeding

 
Bitten Stegosaurus plate close-up, showing how well the damage matches the front of an Allosaurus "mouth"

Many paleontologists accept Allosaurus as an active predator of large animals. There is dramatic evidence for allosaur attacks on Stegosaurus, including an Allosaurus tail vertebra with a partially healed puncture wound that fits a Stegosaurus tail spike, and a Stegosaurus neck plate with a U-shaped wound that correlates well with an Allosaurus snout.[125] Sauropods 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.[126] 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.[31] Another possibility is that it preferred to hunt juveniles instead of fully grown adults.[97][50] Research in the 1990s and the first decade of the 21st century may have found other solutions to this question. Robert T. Bakker, comparing Allosaurus to Cenozoic saber-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 saber 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.[28]

 
A. fragilis showing its maximum possible gape, based on Bakker (1998) and Rayfield et al. (2001)

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 8,724 N,[27][127] but the skull could withstand nearly 55,500 N of vertical force against the tooth row.[27] The authors suggested that Allosaurus used its skull like a machete 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.[27] 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.[128] 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.[129] 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.[44] 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.[97] This is compatible with other evidence that the forelimbs were strong and capable of restraining prey.[107] Studies done by Stephen Lautenschager et al. from the University of Bristol also indicate Allosaurus could open its jaws quite wide and sustain considerable muscle force. When compared with Tyrannosaurus and the therizinosaurid Erlikosaurus in the same study, it was found that Allosaurus had a wider gape than either; the animal was capable of opening its jaws to a 92-degree angle at maximum. The findings also indicate that large carnivorous dinosaurs, like modern carnivores, had wider jaw gapes than herbivores.[130][131]

A biomechanical study published in 2013 by Eric Snively and colleagues found that Allosaurus had an unusually low attachment point on the skull for the longissimus capitis superficialis neck muscle compared to other theropods such as Tyrannosaurus. This would have allowed the animal to make rapid and forceful vertical movements with the skull. The authors found that vertical strikes as proposed by Bakker and Rayfield are consistent with the animal's capabilities. They also found that the animal probably processed carcasses by vertical movements in a similar manner to falcons, such as kestrels: the animal could have gripped prey with the skull and feet, then pulled back and up to remove flesh. This differs from the prey-handling envisioned for tyrannosaurids, which probably tore flesh with lateral shakes of the skull, similar to crocodilians.[132] In addition, Allosaurus was able to "move its head and neck around relatively rapidly and with considerable control", at the cost of power.[133]

 
Allosaurus and Stegosaurus skeletons, the Denver Museum of Nature and Science

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 crocodilians. As with crocodilians, this may have been enough to judge prey distance and time attacks.[134] The arms, compared with those of other theropods, were suited for both grasping prey at a distance or clutching it close,[107] and the articulation of the claws suggests that they could have been used to hook things.[17] Finally, the top speed of Allosaurus has been estimated at 30 to 55 kilometers per hour (19 to 34 miles per hour).[135]

A paper on the cranio-dental morphology of Allosaurus and how it worked has deemed the hatchet jaw attack unlikely, reinterpreting the unusually wide gape as an adaptation to allow Allosaurus to deliver a muscle-driven bite to large prey, with the weaker jaw muscles being a trade-off to allow for the widened gape.[136]

Social behavior

 
The holotype dentary of Labrosaurus ferox, which may have been injured by the bite of another A. fragilis

It has been speculated since the 1970s that Allosaurus preyed on sauropods and other large dinosaurs by hunting in groups.[137] Such a depiction is common in semitechnical and popular dinosaur literature.[12][116][50] 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 lairs for their young to eat until they were grown, and prevented other carnivores from scavenging on the food.[30] However, there is actually little evidence of gregarious behavior in theropods,[44] and social interactions with members of the same species would have included antagonistic encounters, as shown by injuries to gastralia[34] 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 or to settle territorial disputes.[138]

Although Allosaurus may have hunted in packs,[139] it has been argued that Allosaurus and other theropods had largely aggressive interactions instead of cooperative interactions with other members of their own species. The study in question noted that cooperative hunting of prey much larger than an individual predator, as is commonly inferred for theropod dinosaurs, is rare among vertebrates in general, and modern diapsid carnivores (including lizards, crocodiles, and birds) rarely cooperate to hunt in such a way. Instead, they are typically territorial and will kill and cannibalize intruders of the same species, and will also do the same to smaller individuals that attempt to eat before they do when aggregated at feeding sites. According to this interpretation, the accumulation of remains of multiple Allosaurus individuals at the same site; e.g., in the Cleveland–Lloyd Quarry, are not due to pack hunting, but to the fact that Allosaurus individuals were drawn together to feed on other disabled or dead allosaurs, and were sometimes killed in the process. 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 crocodiles and Komodo dragons. The same interpretation applies to Bakker's lair sites.[140] There is some evidence for cannibalism in Allosaurus, including Allosaurus shed teeth found among rib fragments, possible tooth marks on a shoulder blade,[141] and cannibalized allosaur skeletons among the bones at Bakker's lair sites.[142]

Brain and senses

 
Endocast (cast of the brain cavity) of Allosaurus

The brain of Allosaurus, as interpreted from spiral CT scanning of an endocast, was more consistent with crocodilian brains than those of the other living archosaurs, birds. The structure of the 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 bulbs were large and seem to have been well suited for detecting odors, although the area for evaluating smells was relatively small.[29]

Paleopathology

 
Mounted A. fragilis skeleton (USNM4734), which has several healed injuries

In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma rather than singular events they are more likely to be caused by the behavior of the animal than other kinds of injury. Stress fractures and tendon avulsions occurring in the forelimb have special behavioral significance since while injuries to the feet could be caused by running or migration, resistant prey items are the most probable source of injuries to the hand. Allosaurus was one of only two theropods examined in the study to exhibit a tendon avulsion, and in both cases the avulsion occurred on the forelimb. When the researchers looked for stress fractures, they found that Allosaurus had a significantly greater number of stress fractures than Albertosaurus, Ornithomimus or Archaeornithomimus. Of the 47 hand bones the researchers studied, three were found to contain stress fractures. Of the feet, 281 bones were studied and 17 were found to have stress fractures. The stress fractures in the foot bones "were distributed to the proximal phalanges" and occurred across all three weight-bearing toes in "statistically indistinguishable" numbers. Since the lower end of the third metatarsal would have contacted the ground first while an allosaur was running, it would have borne the most stress. If the allosaurs' stress fractures were caused by damage accumulating while walking or running this bone should have experience more stress fractures than the others. The lack of such a bias in the examined Allosaurus fossils indicates an origin for the stress fractures from a source other than running. The authors conclude that these fractures occurred during interaction with prey, like an allosaur trying to hold struggling prey with its feet. The abundance of stress fractures and avulsion injuries in Allosaurus provide evidence for "very active" predation-based rather than scavenging diets.[143]

The left scapula and fibula of an Allosaurus fragilis specimen catalogued as USNM 4734 are both pathological, both probably due to healed fractures. The specimen USNM 8367 preserved several pathological gastralia which preserve evidence of healed fractures near their middle. Some of the fractures were poorly healed and "formed pseudoarthroses". A specimen with a fractured rib was recovered from the Cleveland-Lloyd Quarry. Another specimen had fractured ribs and fused vertebrae near the end of the tail. An apparent subadult male Allosaurus fragilis was reported to have extensive pathologies, with a total of fourteen separate injuries. The specimen MOR 693 had pathologies on five ribs, the sixth neck vertebra, the third, eighth, and thirteenth back vertebrae, the second tail vertebra and its chevron, the gastralia right scapula, manual phalanx I left ilium metatarsals III and V, the first phalanx of the third toe and the third phalanx of the second. The ilium had "a large hole...caused by a blow from above". The near end of the first phalanx of the third toe was afflicted by an involucrum.[144]

 
Skeletal restoration of "Big Al II" showing bones with pathologies

Other pathologies reported in Allosaurus include:[122][144]

  • Willow breaks in two ribs
  • Healed fractures in the humerus and radius
  • Distortion of joint surfaces in the foot, possibly due to osteoarthritis or developmental issues
  • Osteopetrosis along the endosteal surface of a tibia.
  • Distortions of the joint surfaces of the tail vertebrae, possibly due to osetoarthritis or developmental issues
  • "[E]xtensive 'neoplastic' ankylosis of caudals", possibly due to physical trauma, as well as the fusion of chevrons to centra
  • Coossification of vertebral centra near the end of the tail
  • Amputation of a chevron and foot bone, both possibly a result of bites
  • "[E]xtensive exostoses" in the first phalanx of the third toe
  • Lesions similar to those caused by osteomyelitis in two scapulae
  • Bone spurs in a premaxilla, ungual, and two metacarpals
  • Exostosis in a pedal phalanx possibly attributable to an infectious disease
  • A metacarpal with a round depressed fracture

Paleoecology

 
Restoration of Barosaurus rearing to defend itself against a pair of A. fragilis

Allosaurus was the most common large theropod in the vast tract of Western American fossil-bearing rock known as the Morrison Formation, accounting for 70 to 75% of theropod specimens,[97] and as such was at the top trophic level of the Morrison food chain.[145] The Morrison Formation is interpreted as a semiarid environment with distinct wet and dry seasons, and flat floodplains.[146] Vegetation varied from river-lining forests of conifers, tree ferns, and ferns (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum.[147]

 
Locations in the Morrison Formation (yellow) where Allosaurus remains have been found

The Morrison Formation has been a rich fossil hunting ground. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, ferns, cycads, ginkgoes, and several families of conifers. Animal fossils discovered include bivalves, snails, ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphs, several species of pterosaur, numerous dinosaur species, and early mammals such as docodonts, multituberculates, symmetrodonts, and triconodonts. Dinosaurs known from the Morrison include the theropods Ceratosaurus, Ornitholestes, Tanycolagreus, and Torvosaurus, the sauropods Haplocanthosaurus, Camarasaurus, Cathetosaurus, Brachiosaurus, Suuwassea, Apatosaurus, Brontosaurus, Barosaurus, Diplodocus, Supersaurus, Amphicoelias, and Maraapunisaurus, and the ornithischians Camptosaurus, Dryosaurus, and Stegosaurus.[148] Allosaurus is commonly found at the same sites as Apatosaurus, Camarasaurus, Diplodocus, and Stegosaurus.[149] The Late Jurassic formations of Portugal where Allosaurus is present are interpreted as having been similar to the Morrison, but with a stronger 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 Stegosaurus), or have a close counterpart (Brachiosaurus and Lusotitan, Camptosaurus and Draconyx).[150]

 
Dry season at the Mygatt-Moore Quarry showing Ceratosaurus (center) and Allosaurus fighting over the desiccated carcass of another theropod

Allosaurus coexisted with fellow large theropods Ceratosaurus and Torvosaurus in both the United States and Portugal.[150] The three appear to have had different ecological niches, based on anatomy and the location of fossils. Ceratosaurus and Torvosaurus 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 Allosaurus was more compact, with longer legs, faster but less maneuverable, and seems to have preferred dry floodplains.[142] Ceratosaurus, better known than Torvosaurus, differed noticeably from Allosaurus in functional anatomy by having a taller, narrower skull with large, broad teeth.[19] Allosaurus was itself a potential food item to other carnivores, as illustrated by an Allosaurus 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.[151] A bone assemblage in the Upper Jurassic Mygatt-Moore Quarry preserves an unusually high occurrence of theropod bite marks, most of which can be attributed to Allosaurus and Ceratosaurus, while others could have been made by Saurophaganax or Torvosaurus given the size of the striations. While the position of the bite marks on the herbivorous dinosaurs is consistent with predation or early access to remains, bite marks found on Allosaurus material suggest scavenging, either from the other theropods or from another Allosaurus. The unusually high concentration of theropod bite marks compared to other assemblages could be explained either by a more complete utilization of resources during a dry season by theropods, or by a collecting bias in other localities.[152]

References

  1. ^ a b c d e f Chure, D.J.; Loewen, M.A. (2020). "Cranial anatomy of Allosaurus jimmadseni, a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America". PeerJ. 8: e7803. doi:10.7717/peerj.7803. PMC 6984342. PMID 32002317.
  2. ^ "Allosaurus". Merriam-Webster Dictionary.
  3. ^ "Allosaurus". Dictionary.com Unabridged (Online). n.d.
  4. ^ Leidy, Joseph (1870). "Remarks on Poicilopleuron valens, Clidastes intermedius, Leiodon proriger, Baptemys wyomingensis, and Emys stevensonianus". Proceedings of the Academy of Natural Sciences of Philadelphia. 22: 3–4.
  5. ^ Leidy, Joseph (1873). "Contribution to the extinct vertebrate fauna of the western territories". Report of the U.S. Geological Survey of the Territories I: 14–358.
  6. ^ Liddell & Scott (1980). Greek–English Lexicon, Abridged Edition. Oxford: Oxford University Press. ISBN 978-0-19-910207-5. OCLC 17396377.
  7. ^ a b c Marsh, Othniel Charles (1877). "Notice of new dinosaurian reptiles from the Jurassic formation". American Journal of Science and Arts. 14 (84): 514–516. Bibcode:1877AmJS...14..514M. doi:10.2475/ajs.s3-14.84.514. S2CID 130488291.
  8. ^ Creisler, Ben (7 July 2003). . Dinosauria On-Line. Archived from the original on 5 January 2010. Retrieved 11 September 2007.
  9. ^ a b c d Marsh, Othniel Charles (1878). "Notice of new dinosaurian reptiles". American Journal of Science and Arts. 15 (87): 241–244. Bibcode:1878AmJS...15..241M. doi:10.2475/ajs.s3-15.87.241. S2CID 131371457.
  10. ^ a b Marsh, Othniel Charles (1879). "Principal characters of American Jurassic dinosaurs. Part II". American Journal of Science. Series 3. 17 (97): 86–92. doi:10.2475/ajs.s3-17.97.86. hdl:2027/hvd.32044107172876. S2CID 219247096.
  11. ^ a b Cope, Edward Drinker (1878). "A new opisthocoelous dinosaur". American Naturalist. 12 (6): 406–408. doi:10.1086/272127.
  12. ^ a b c Norman, David B. (1985). "Carnosaurs". The Illustrated Encyclopedia of Dinosaurs: An Original and Compelling Insight into Life in the Dinosaur Kingdom. New York: Crescent Books. pp. 62–67. ISBN 978-0-517-46890-6.
  13. ^ Norell, Mark A.; Gaffney, Eric S.; Dingus, Lowell (1995). Discovering Dinosaurs in the American Museum of Natural History. New York: Knopf. pp. 112–113. ISBN 978-0-679-43386-6.
  14. ^ Breithaupt, Brent H. (1999). "AMNH 5753: The world's first free-standing theropod skeleton". Journal of Vertebrate Paleontology. 19 (3, Suppl): 33A. doi:10.1080/02724634.1999.10011202.
  15. ^ Williston, Samuel Wendell (1878). "American Jurassic dinosaurs". Transactions of the Kansas Academy of Science. 6: 42–46. doi:10.2307/3623553. JSTOR 3623553.
  16. ^ Williston, Samuel Wendell (1901). "The dinosaurian genus Creosaurus, Marsh". American Journal of Science. Series 4. 11 (62): 111–114. Bibcode:1901AmJS...11..111W. doi:10.2475/ajs.s4-11.62.111.
  17. ^ a b c d e f g h Gilmore, Charles W. (1920). "Osteology of the carnivorous dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus" (PDF). Bulletin of the United States National Museum (110): 1–159. doi:10.5479/si.03629236.110.i. hdl:2027/uiug.30112032536010. Archived (PDF) from the original on 9 October 2022.
  18. ^ a b c d e f g h i j k l m n o p q r Madsen, James H. Jr. (1993) [1976]. Allosaurus fragilis: A Revised Osteology. Utah Geological Survey Bulletin 109 (2nd ed.). Salt Lake City: Utah Geological Survey.
  19. ^ a b Henderson, Donald M. (1998). "Skull and tooth morphology as indicators of niche partitioning in sympatric Morrison Formation theropods". Gaia. 15: 219–266.
  20. ^ Stokes, William L. (1945). "A new quarry for Jurassic dinosaurs". Science. 101 (2614): 115–117. Bibcode:1945Sci...101..115S. doi:10.1126/science.101.2614.115-a. PMID 17799203. S2CID 13589884.
  21. ^ Hunt, Adrian P; Lucas, Spencer G.; Krainer, Karl; Spielmann, Justin (2006). "The taphonomy of the Cleveland-Lloyd Dinosaur Quarry, Upper Jurassic Morrison Formation, Utah: a re-evaluation". In Foster, John R.; Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 57–65.
  22. ^ a b Loewen, Mark A.; Sampson, Scott D.; Carrano, Matthew T.; Chure, Daniel J. (2003). "Morphology, taxonomy, and stratigraphy of Allosaurus from the Upper Jurassic Morrison Formation". Journal of Vertebrate Paleontology. 23 (3): 72A. doi:10.1080/02724634.2003.10010538. S2CID 220410105.
  23. ^ "Utah Symbols – State Fossil". Pioneer: Utah's Online Library, State of Utah. from the original on 8 January 2010. Retrieved 16 June 2010.
  24. ^ a b c Smith, David K. (1998). "A morphometric analysis of Allosaurus". Journal of Vertebrate Paleontology. 18 (1): 126–142. Bibcode:1998JVPal..18..126S. doi:10.1080/02724634.1998.10011039.
  25. ^ a b Bybee, Paul J.; Lee, AH; Lamm, ET (2006). "Sizing the Jurassic theropod dinosaur Allosaurus: Assessing growth strategy and evolution of ontogenetic scaling of limbs". Journal of Morphology. 267 (3): 347–359. doi:10.1002/jmor.10406. PMID 16380967. S2CID 35111050.
  26. ^ a b Foster, John R.; Chure, Daniel J. (2006). "Hindlimb allometry in the Late Jurassic theropod dinosaur Allosaurus, with comments on its abundance and distribution". In Foster, John R.; Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 119–122.
  27. ^ a b c d Rayfield, Emily J.; Norman, DB; Horner, CC; Horner, JR; Smith, PM; Thomason, JJ; Upchurch, P (2001). "Cranial design and function in a large theropod dinosaur". Nature. 409 (6823): 1033–1037. Bibcode:2001Natur.409.1033R. doi:10.1038/35059070. PMID 11234010. S2CID 4396729.
  28. ^ a b Bakker, Robert T. (1998). "Brontosaur killers: Late Jurassic allosaurids as sabre-tooth cat analogues". Gaia. 15: 145–158. ISSN 0871-5424.
  29. ^ a b Rogers, Scott W. (1999). "Allosaurus, crocodiles, and birds: Evolutionary clues from spiral computed tomography of an endocast". The Anatomical Record. 257 (5): 163–173. doi:10.1002/(SICI)1097-0185(19991015)257:5<162::AID-AR5>3.0.CO;2-W. PMID 10597341.
  30. ^ a b Bakker, Robert T. (1997). "Raptor Family values: Allosaur parents brought giant carcasses into their lair to feed their young". In Wolberg, Donald L.; Sump, Edmund; Rosenberg, Gary D. (eds.). Dinofest International, Proceedings of a Symposium Held at Arizona State University. Philadelphia: Academy of Natural Sciences. pp. 51–63. ISBN 978-0-935868-94-4.
  31. ^ a b c d e f g h i j k l m n Paul, Gregory S. (1988). "Genus Allosaurus". Predatory Dinosaurs of the World. New York: Simon & Schuster. pp. 307–313. ISBN 978-0-671-61946-6.
  32. ^ a b Chure, Daniel J. (1995). "A reassessment of the gigantic theropod Saurophagus maximus from the Morrison Formation (Upper Jurassic) of Oklahoma, USA". In Ailing Sun; Yuangqing Wang (eds.). Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers. Beijing: China Ocean Press. pp. 103–106. ISBN 978-7-5027-3898-3.
  33. ^ a b Pérez-Moreno, B.P.; Chure, D. J.; Pires, C.; Marques Da Silva, C.; Dos Santos, V.; Dantas, P.; Povoas, L.; Cachao, M.; Sanz, J. L. (1999). (PDF). Journal of the Geological Society. 156 (3): 449–452. Bibcode:1999JGSoc.156..449P. doi:10.1144/gsjgs.156.3.0449. S2CID 130952546. Archived from the original (PDF) on 25 October 2007.
  34. ^ a b c d Chure, Daniel J. (2000). "Observations on the morphology and pathology of the gastral basket of Allosaurus, based on a new specimen from Dinosaur National Monument". Oryctos. 3: 29–37. ISSN 1290-4805.
  35. ^ a b Breithaupt, Brent (1996). "The discovery of a nearly complete Allosaurus from the Jurassic Morrison Formation, eastern Bighorn Basin, Wyoming". In Brown, C.E.; Kirkwood, S.C.; Miller, T.S. (eds.). Forty-Seventh Annual Field Conference Guidebook. Casper, Wyoming: Wyoming Geological Association. pp. 309–313. OCLC 36004754.
  36. ^ . GeoScience Adventures. 24 July 2007. Archived from the original on 3 December 2007. Retrieved 27 September 2007.
  37. ^ a b Breithaupt, Brent H. . Archived from the original on 7 January 2010. Retrieved 3 October 2007.
  38. ^ a b Hanna, Rebecca R. (2002). "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 of Vertebrate Paleontology. 22 (1): 76–90. doi:10.1671/0272-4634(2002)022[0076:MIAIIA]2.0.CO;2. ISSN 0272-4634. S2CID 85654858.
  39. ^ Wilkin, Jack (24 November 2019). "Review of Pathologies on MOR 693: An Allosaurus from the Late Jurassic of Wyoming and Implications for Understanding Allosaur Immune Systems". PaleorXiv. doi:10.31233/osf.io/f3rh6. S2CID 242466868.
  40. ^ Foth, C.; Evers, S.; Pabst, B.; Mateus, O.; Flisch, A.; Patthey, M.; Rauhut, O. W. M. (2015). "New insights into the lifestyle of Allosaurus (Dinosauria: Theropoda) based on another specimen with multiple pathologies". PeerJ. 3: e824v1. doi:10.7717/peerj.940. PMC 4435507. PMID 26020001.
  41. ^ Galton, Peter M.; Carpenter, Kenneth; Dalman, Sebastian G. (2015). "The holotype pes of the Morrison dinosaur Camptonotus amplus Marsh, 1879 (Upper Jurassic, western USA) – is it Camptosaurus, Sauropoda or Allosaurus?". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 275 (3): 317–335. doi:10.1127/njgpa/2015/0467.
  42. ^ a b c d e f g h i j Chure, Daniel J. (2000). A new species of Allosaurus from the Morrison Formation of Dinosaur National Monument (Utah–Colorado) and a revision of the theropod family Allosauridae. PhD dissertation. Columbia University.
  43. ^ a b c Mateus, Octávio; Walen, Aart; Antunes, Miguel Telles (2006). "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". In Foster, John R.; Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 123–129.
  44. ^ a b c d e f g h i j k l m n o p q r s t Holtz, Thomas R. Jr.; Molnar, Ralph E.; Currie, Philip J. (2004). "Basal Tetanurae". In Weishampel David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 71–110. ISBN 978-0-520-24209-8.
  45. ^ Dalman, Sebastian G. (2014). "Osteology of a large allosauroid theropod from the Upper Jurassic (Tithonian) Morrison Formation of Colorado, USA". Volumina Jurassica. 12 (2): 159–180.
  46. ^ a b c Malafaia, Elisabete; Dantas, Pedro; Ortega, Francisco; Escaso, Fernando (2007). "Nuevos restos de Allosaurus fragilis (Theropoda: Carnosauria) del yacimiento de Andrés (Jurásico Superior; centro-oeste de Portugal)" [New remains of Allosaurus fragilis (Theropoda: Carnosauria) of the Andrés deposit (Upper Jurassic; central-west Portugal)] (PDF). Cantera Paleontológica (in Spanish and English): 255–271. Archived (PDF) from the original on 9 October 2022.
  47. ^ Evers, Serjoscha W.; Foth, Christian; Rauhut, Oliver W.M. (7 February 2020). "Notes on the cheek region of the Late Jurassic theropod dinosaur Allosaurus". PeerJ. 8: e8493. doi:10.7717/peerj.8493. ISSN 2167-8359. PMC 7008823. PMID 32076581.
  48. ^ a b Glut, Donald F. (2003). "Allosaurus". Dinosaurs: The Encyclopedia. 3rd Supplement. Jefferson, North Carolina: McFarland & Co. pp. 221–233. ISBN 978-0-7864-1166-5.
  49. ^ "New species of Allosaurus discovered in Utah". phys.org.
  50. ^ a b c d Lessem, Don; Glut, Donald F. (1993). "Allosaurus". The Dinosaur Society's Dinosaur Encyclopedia. Random House. pp. 19–20. ISBN 978-0-679-41770-5. OCLC 30361459.
  51. ^ a b Smith, David K. (1996). "A discriminant analysis of Allosaurus population using quarries as the operational units". Museum of Northern Arizona Bulletin. 60: 69–72.
  52. ^ a b Smith, David K. (1999). "Patterns of size-related variation within Allosaurus". Journal of Vertebrate Paleontology. 19 (2): 402–403. Bibcode:1999JVPal..19..402S. doi:10.1080/02724634.1999.10011153.
  53. ^ a b c Carpenter, Kenneth (2010). "Variation in a population of Theropoda (Dinosauria): Allosaurus from the Cleveland-Lloyd Quarry (Upper Jurassic), Utah, USA". Paleontological Research. 14 (4): 250–259. doi:10.2517/1342-8144-14.4.250. S2CID 84635714.
  54. ^ a b Paul, Gregory S.; Carpenter, Kenneth (2010). "Allosaurus Marsh, 1877 (Dinosauria, Theropoda): proposed conservation of usage by designation of a neotype for its type species Allosaurus fragilis Marsh, 1877". Bulletin of Zoological Nomenclature. 67 (1): 53–56. doi:10.21805/bzn.v67i1.a7. S2CID 81735811.
  55. ^ Marsh, Othniel Charles (1884). "Principal characters of American Jurassic dinosaurs. Part VIII". American Journal of Science. Series 3. 27 (160): 329–340. Bibcode:1884AmJS...27..329M. doi:10.2475/ajs.s3-27.160.329. S2CID 131076004.
  56. ^ a b c d e Madsen, James H.; Welles, Samuel P. (2000). Ceratosaurus (Dinosauria, Theropoda), a Revised Osteology. Miscellaneous Publication, 00-2. Utah Geological Survey.
  57. ^ a b Marsh, Othniel Charles (1896). "The dinosaurs of North America". United States Geological Survey, 16th Annual Report, 1894–95. 55: 133–244.
  58. ^ "MADSENIUS". dinoruss.com. 27 March 2006. from the original on 27 June 2008. Retrieved 18 December 2020.
  59. ^ Lambert, D. (1990) The Dinosaur Data Book, Facts on File, Oxford, England: 320 pp.
  60. ^ a b "Carnosauria". www.theropoddatabase.com. Retrieved 18 December 2020.
  61. ^ Bakker, 1997. Raptor family values: Allosaur parents brought great carcasses into their lair to feed their young. In Wolberg, Sump and Rosenberg (eds). Dinofest International, Proceedings of a Symposium, Academy of Natural Sciences. 51–63.
  62. ^ . dml.cmnh.org. Archived from the original on 24 June 2021. Retrieved 1 January 2019.
  63. ^ Marsh, Othniel Charles (1888). "Notice of a new genus of Sauropoda and other new dinosaurs from the Potomac Formation". American Journal of Science. Series 3. 35 (205): 89–94. Bibcode:1888AmJS...35...89M. doi:10.2475/ajs.s3-35.205.89. S2CID 130879860.
  64. ^ a b Lull, Richard Swann (1911). "The Reptilia of the Arundel Formation". Maryland Geological Survey: Lower Cretaceous: 173–178.
  65. ^ Hay, Oliver Perry (1902). "Bibliography and catalogue of the fossil vertebrata of North America". Bulletin. doi:10.3133/b179.
  66. ^ Hay, Oliver Perry (1908). "On certain genera and species of carnivorous dinosaurs, with special reference to Ceratosaurus nasicornis Marsh". Proceedings of the United States National Museum. 35 (1648): 351–366. doi:10.5479/si.00963801.35-1648.351. hdl:10088/14046.
  67. ^ "Neotheropoda". The Theropod Database. Retrieved 28 September 2018.
  68. ^ Marsh, O.C. (1878). "Notice of new dinosaurian reptiles" (PDF). American Journal of Science. 15 (87): 241–244. Bibcode:1878AmJS...15..241M. doi:10.2475/ajs.s3-15.87.241. S2CID 131371457. Archived (PDF) from the original on 9 October 2022.
  69. ^ Riabinin, Anatoly Nikolaenvich (1914). "Zamtka o dinozavry ise Zabaykalya". Trudy Geologichyeskago Muszeyah Imeni Petra Velikago Imperatorskoy Academiy Nauk (in Russian). 8 (5): 133–140.
  70. ^ Molnar, Ralph E.; Kurzanov, Sergei M.; Dong Zhiming (1990). "Carnosauria". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (1st ed.). Berkeley: University of California Press. pp. 169–209. ISBN 978-0-520-06727-1.
  71. ^ a b c Carrano, Benson; Sampson (2012). "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 10 (2): 211–300. doi:10.1080/14772019.2011.630927. S2CID 85354215.
  72. ^ Greppin, J.B. (1870). "Description geologique du Jura bernois et de quelques districts adjacents". Beiträge zur Geologischen Karte der Schweiz (in French). 8: 1–357.
  73. ^ Olshevsky, 1978. The archosaurian taxa (excluding the Crocodylia). Mesozoic Meanderings. 1, 1–50.
  74. ^ Olshevsky, G., 1991, A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2, 196 pp
  75. ^ a b c d Glut, Donald F. (1997). "Allosaurus". Dinosaurs: The Encyclopedia. Jefferson, North Carolina: McFarland & Co. pp. 105–117. ISBN 978-0-89950-917-4.
  76. ^ "Apatodonmirus". The Theropod Database. Retrieved 28 September 2018.
  77. ^ Osborn, Henry Fairfield; Mook, Charles C. (1921). "Camarasaurus, Amphicoelias, and other sauropods of Cope". Memoirs of the American Museum of Natural History. New Series. 3 (1): 247–387. Bibcode:1919GSAB...30..379O. doi:10.1130/GSAB-30-379. hdl:2027/mdp.39015042532476.
  78. ^ Paul, G.S.; Carpenter, K. (2010). "Case 3506: Allosaurus Marsh, 1877 (Dinosauria, Theropoda): proposed conservation of usage by designation of a neotype for its type species Allosaurus fragilis Marsh, 1877" (PDF). Bulletin of Zoological Nomenclature. 67 (1): 53–56. doi:10.21805/bzn.v67i1.a7. S2CID 81735811.
  79. ^ Janensch, Werner (1920). "Uber Elaphrosaurus bambergi und die Megalosaurier aus den Tendaguru-Schichten Deutsch-Ostafricas". Sitzungsberichte Gesellschaft Naturforschender Freunde Berlin. 8: 225–235.
  80. ^ a b Tykoski, Ronald S.; and Rowe, Timothy. (2004). "Ceratosauria", in The Dinosauria (2nd). 47–70.
  81. ^ Janensch, Werner (1925). "Die Coelurosaurier und Theropoden der Tendaguru-Schichten Deutsch-Ostafrikas". Palaeontographica (in German). 1 (Suppl. 7): 1–99.
  82. ^ Rauhut, Oliver W.M. (2005). "Post-cranial remains of 'coelurosaurs' (Dinosauria, Theropoda) from the Late Jurassic of Tanzania". Geological Magazine. 142 (1): 97–107. Bibcode:2005GeoM..142...97R. doi:10.1017/S0016756804000330. S2CID 131517482.
  83. ^ Rauhut, Oliver W. M. "Theropod dinosaurs from the Late Jurassic of Tendaguru (Tanzania)". Special Papers in Palaeontology. 86: 195–239.
  84. ^ a b c d Mortimer, Mickey (21 July 2003). "And the largest Theropod is..." The Dinosaur Mailing List. from the original on 25 March 2010. Retrieved 8 September 2007.
  85. ^ Kurzanov, Sergei S.; Efimov, Mikhail B.; Gubin, Yuri M. (2003). "New archosaurs from the Jurassic of Siberia and Mongolia". Paleontological Journal. 37 (1): 53–57.
  86. ^ Glut, Donald F. (1982). The New Dinosaur Dictionary. Secaucus, NJ: Citadel Press. p. 44. ISBN 978-0-8065-0782-8.
  87. ^ Molnar, Ralph E.; Flannery, Timothy F.; Rich, Thomas H.V. (1981). "An allosaurid theropod dinosaur from the Early Cretaceous of Victoria, Australia". Alcheringa. 5 (2): 141–146. doi:10.1080/03115518108565427.
  88. ^ Welles, Samuel P. (1983). "Allosaurus (Saurischia, Theropoda) not yet in Australia". Journal of Paleontology. 57 (2): 196.
  89. ^ Molnar, Ralph E.; Flannery, Timothy F.; Rich, Thomas H.V. (1985). "Aussie Allosaurus after all". Journal of Paleontology. 59 (6): 1511–1535.
  90. ^ Chure, Daniel J. (1998). "A reassessment of the Australian Allosaurus and its implications for the Australian refugium concept". Journal of Vertebrate Paleontology. 18 (3, Suppl): 1–94. doi:10.1080/02724634.1998.10011116.
  91. ^ Azuma, Yoichi; Currie, Philip J. (2000). "A new carnosaur (Dinosauria: Theropoda) from the Lower Cretaceous of Japan" (PDF). Journal of Vertebrate Paleontology. 37 (12): 1735–1753. Bibcode:2000CaJES..37.1735A. doi:10.1139/e00-064.
  92. ^ Hocknull, Scott A.; White, Matt A.; Tischler, Travis R.; Cook, Alex G.; Calleja, Naomi D.; Sloan, Trish; Elliott, David A. (2009). Sereno, Paul (ed.). "New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia". PLOS ONE. 4 (7): e6190. Bibcode:2009PLoSO...4.6190H. doi:10.1371/journal.pone.0006190. PMC 2703565. PMID 19584929.
  93. ^ Agnolin, F. L.; Ezcurra, M. D.; Pais, D. F.; Salisbury, S. W. (2010). "A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: Evidence for their Gondwanan affinities" (PDF). Journal of Systematic Palaeontology. 8 (2): 257–300. doi:10.1080/14772011003594870. S2CID 130568551. Archived (PDF) from the original on 9 October 2022.
  94. ^ a b c Paul, Gregory S. (2010). The Princeton Field Guide to Dinosaurs. Princeton University Press. pp. 94–96.
  95. ^ Campione, N. E.; Evans, D. C.; Brown, C. M.; Carrano, M. T. (2014). "Body mass estimation in non‐avian bipeds using a theoretical conversion to quadruped stylopodial proportions". Methods in Ecology and Evolution. 5 (9): 913−923. doi:10.1111/2041-210X.12226. hdl:10088/25281.
  96. ^ a b Foster, John R. (2003). Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. New Mexico Museum of Natural History and Science Bulletin 23. Albuquerque: New Mexico Museum of Natural History and Science. p. 37.
  97. ^ a b c d Foster, John (2007). "Allosaurus fragilis". Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Bloomington, Indiana: Indiana University Press. pp. 170–176. ISBN 978-0-253-34870-8. OCLC 77830875.
  98. ^ Bates, Karl T.; Falkingham, Peter L.; Breithaupt, Brent H.; Hodgetts, David; Sellers, William I.; Manning, Phillip L. (2009). "How big was 'Big Al'? Quantifying the effect of soft tissue and osteological unknowns on mass predictions for Allosaurus (Dinosauria:Theropoda)". Palaeontologia Electronica. 12 (3): unpaginated. from the original on 25 December 2009. Retrieved 13 December 2009.
  99. ^ Foster, John. 2007. Jurassic West: the Dinosaurs of the Morrison Formation and Their World. Bloomington, Indiana:Indiana University Press. p. 117.
  100. ^ Motani, Ryosuke (2021). "Sex estimation from morphology in living animals and dinosaurs". Zoological Journal of the Linnean Society. 192 (4): 1029–1044. doi:10.1093/zoolinnean/zlaa181 – via academic.oup.com.
  101. ^ Molnar, Ralph E. (1977). "Analogies in the evolution of combat and display structures in ornithopods and ungulates". Evolutionary Theory. 3: 165–190.
  102. ^ Paul, Gregory S. (1988). Predatory Dinosaurs of the World. 91 and Figure 4–5 (93).
  103. ^ 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 10 neck and 13 back vertebrae.
  104. ^ Paul, Gregory S. (1988). Predatory Dinosaurs of the World. 277.
  105. ^ Chure, Daniel J.; Madsen, James (1996). "On the presence of furculae in some non-maniraptoran theropods". Journal of Vertebrate Paleontology. 16 (3): 573–577. Bibcode:1996JVPal..16..573C. doi:10.1080/02724634.1996.10011341.
  106. ^ Middleton, Kevin M. (2000). (PDF). Zoological Journal of the Linnean Society. 128 (2): 149–187. doi:10.1006/zjls.1998.0193. Archived from the original (PDF) on 25 October 2007. Retrieved 25 October 2007.
  107. ^ a b c Carpenter, Kenneth (2002). "Forelimb biomechanics of nonavian theropod dinosaurs in predation". Senckenbergiana Lethaea. 82 (1): 59–76. doi:10.1007/BF03043773. S2CID 84702973.
  108. ^ Martin, A.J. (2006). Introduction to the Study of Dinosaurs. Second Edition. Oxford, Blackwell Publishing. 560 pp. ISBN 1-4051-3413-5.
  109. ^ 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.
  110. ^ a b c Hendrickx, Christophe; Bell, Phil R.; Pittman, Michael; Milner, Andrew R. C.; Cuesta, Elena; O'Connor, Jingmai; Loewen, Mark; Currie, Philip J.; Mateus, Octávio; Kaye, Thomas G.; Delcourt, Rafael (June 2022). "Morphology and distribution of scales, dermal ossifications, and other non‐feather integumentary structures in non‐avialan theropod dinosaurs". Biological Reviews. 97 (3): 960–1004. doi:10.1111/brv.12829. ISSN 1464-7931. PMID 34991180. S2CID 245820672.
  111. ^ von Huene, Friedrich (1926). "The carnivorous Saurischia in the Jura and Cretaceous formations, principally in Europe". Revista del Museo de La Plata. 29: 35–167.
  112. ^ Romer, Alfred S. (1956). Osteology of the Reptiles. Chicago: University of Chicago Press. ISBN 978-0-89464-985-1.
  113. ^ Romer, Alfred S. (1966). Vertebrate Paleontology (Third ed.). Chicago: University of Chicago Press. ISBN 978-0-7167-1822-2.
  114. ^ Steel, R. (1970). "Part 14. Saurischia. Handbuch der Paläoherpetologie/Encyclopedia of Paleoherpetology". Gustav Fischer Verlag, Stuttgart: 1–87.
  115. ^ Walker, Alick D. (1964). "Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs". Philosophical Transactions of the Royal Society B. 248 (744): 53–134. Bibcode:1964RSPTB.248...53W. doi:10.1098/rstb.1964.0009. JSTOR 2416617. S2CID 86378219.
  116. ^ a b Lambert, David; the Diagram Group (1983). "Allosaurids". A Field Guide to Dinosaurs. New York: Avon Books. pp. 80–81. ISBN 978-0-380-83519-5.
  117. ^ Lambert, David; the Diagram Group (1990). "Allosaurids". The Dinosaur Data Book. New York: Avon Books. p. 130. ISBN 978-0-380-75896-8.
  118. ^ a b Benson, R.B.J.; Carrano, M.T.; Brusatte, S.L. (2010). "A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic" (PDF). Naturwissenschaften. 97 (1): 71–78. Bibcode:2010NW.....97...71B. doi:10.1007/s00114-009-0614-x. PMID 19826771. S2CID 22646156.
  119. ^ Paul, Gregory S. (1988). "The allosaur-tyrannosaur group", Predatory Dinosaurs of the World. 301–347.
  120. ^ Holtz, Thomas R. Jr. (1994). "The phylogenetic position of the Tyrannosauridae: Implications for theropod systematics". Journal of Paleontology. 68 (5): 1100–1117. Bibcode:1994JPal...68.1100H. doi:10.1017/S0022336000026706. JSTOR 1306180. S2CID 129684676.
  121. ^ Lee, Andrew H.; Werning, S (2008). "Sexual maturity in growing dinosaurs does not fit reptilian growth models". Proceedings of the National Academy of Sciences of the United States of America. 105 (2): 582–587. Bibcode:2008PNAS..105..582L. doi:10.1073/pnas.0708903105. PMC 2206579. PMID 18195356.
  122. ^ a b Chinsamy, A.; Tumarkin-Deratzian, A. (2009). "Pathological Bone Tissues in a Turkey Vulture and a Nonavian Dinosaur: Implications for Interpreting Endosteal Bone and Radial Fibrolamellar Bone in Fossil Dinosaurs". Anat. Rec. 292 (9): 1478–1484. doi:10.1002/ar.20991. PMID 19711479. S2CID 41596233.
  123. ^ . Science Daily. 15 March 2016. Archived from the original on 14 April 2016.
  124. ^ Loewen, Mark A. (2002). "Ontogenetic changes in hindlimb musculature and function in the Late Jurassic theropod Allosaurus". Journal of Vertebrate Paleontology. 22 (3, Suppl): 80A.
  125. ^ Carpenter, Kenneth; Sanders, Frank; McWhinney, Lorrie A.; Wood, Lowell (2005). "Evidence for predator-prey relationships: Examples for Allosaurus and Stegosaurus". In Carpenter, Kenneth (ed.). The Carnivorous Dinosaurs. Bloomington and Indianapolis: Indiana University Press. pp. 325–350. ISBN 978-0-253-34539-4.
  126. ^ Fastovsky, David E.; and Smith, Joshua B. (2004). "Dinosaur Paleoecology", in The Dinosauria (2nd ed.). 614–626.
  127. ^ Bates, K. T.; Falkingham, P.L. (29 February 2012). "Estimating maximum bite performance in Tyrannosaurus rex using multi-body dynamics". Biological Letters. 8 (4): 660–664. doi:10.1098/rsbl.2012.0056. PMC 3391458. PMID 22378742.
  128. ^ Frazzetta, T. H.; Kardong, K. V. (2002). "Prey attack by a large theropod dinosaur". Nature. 416 (6879): 387–388. Bibcode:2002Natur.416..387F. doi:10.1038/416387a. PMID 11919619. S2CID 4388901.
  129. ^ Rayfield, Emily J.; Norman, D. B.; Upchurch, P. (2002). "Prey attack by a large theropod dinosaur: Response to Frazzetta and Kardong, 2002". Nature. 416 (6879): 388. Bibcode:2002Natur.416..388R. doi:10.1038/416388a. S2CID 4392259.
  130. ^ Lautenschlager, Stephan (4 November 2015). "Estimating cranial musculoskeletal constraints in theropod dinosaurs". Royal Society Open Science. 2 (11): 150495. Bibcode:2015RSOS....250495L. doi:10.1098/rsos.150495. PMC 4680622. PMID 26716007.
  131. ^ "Better to eat you with? How dinosaurs' jaws influenced diet". Science Daily. 3 November 2015. from the original on 7 March 2016.
  132. ^ Snively, Eric.; Cotton, John R.; Ridgely, Ryan; Witmer, Lawrence M. (2013). "Multibody dynamics model of head and neck function in Allosaurus (Dinosauria, Theropoda)". Palaeontologia Electronica. 16 (2). doi:10.26879/338.
  133. ^ Ohio University (22 May 2013). "Allosaurus fed more like a falcon than a crocodile: Engineering, anatomy work reveals differences in dinosaur feeding styles". ScienceDaily. Retrieved 22 May 2013.
  134. ^ Stevens, Kent A. (2006). "Binocular vision in theropod dinosaurs". Journal of Vertebrate Paleontology. 26 (2): 321–330. doi:10.1671/0272-4634(2006)26[321:BVITD]2.0.CO;2. ISSN 0272-4634. S2CID 85694979.
  135. ^ Christiansen, Per (1998). "Strength indicator values of theropod long bones, with comments on limb proportions and cursorial potential". Gaia. 15: 241–255. ISSN 0871-5424.
  136. ^ Anton, M.; Sánchez, I.; Salesa, Manuel; Turner, A (2003). "The muscle-powered bite of Allosaurus (Dinosauria; Theropoda): An interpretation of cranio-dental morphology" (PDF). Estudios Geológicos. 59 (5): 313–323. doi:10.3989/egeol.03595-6106. Archived (PDF) from the original on 9 October 2022.
  137. ^ Farlow, James O. (1976). "Speculations about the diet and foraging behavior of large carnivorous dinosaurs". American Midland Naturalist. 95 (1): 186–191. doi:10.2307/2424244. JSTOR 2424244.
  138. ^ Tanke, Darren H. (1998). "Head-biting behavior in theropod dinosaurs: Paleopathological evidence". Gaia (15): 167–184.
  139. ^ Currie, Philip J. (1999). "Theropods". In Farlow, James; Brett-Surman, M.K. (eds.). The Complete Dinosaur. Indiana: Indiana University Press. p. 228. ISBN 978-0-253-21313-6.
  140. ^ Roach, Brian T.; Brinkman, Daniel L. (2007). "A reevaluation of cooperative pack hunting and gregariousness in Deinonychus antirrhopus and other nonavian theropod dinosaurs". Bulletin of the Peabody Museum of Natural History. 48 (1): 103–138. doi:10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2. S2CID 84175628.
  141. ^ Goodchild Drake, Brandon (2004). "A new specimen of Allosaurus from north-central Wyoming". Journal of Vertebrate Paleontology. 24 (3, Suppl): 65A. doi:10.1080/02724634.2004.10010643. S2CID 220415208.
  142. ^ a b Bakker, Robert T.; Bir, Gary (2004). "Dinosaur crime scene investigations: theropod behavior at Como Bluff, Wyoming, and the evolution of birdness". In Currie, Philip J.; Koppelhus, Eva B.; Shugar, Martin A.; Wright, Joanna L. (eds.). Feathered Dragons: Studies on the Transition from Dinosaurs to Birds. Bloomington and Indianapolis: Indiana University Press. pp. 301–342. ISBN 978-0-253-34373-4.
  143. ^ Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331–336.
  144. ^ a b Molnar, R.E. (2001). "Theropod paleopathology: a literature survey". In Tanke, D.H.; Carpenter, K. (eds.). Mesozoic Vertebrate Life. Indiana University Press. pp. 337–363.
  145. ^ Foster, John R. (2003). Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. New Mexico Museum of Natural History and Science Bulletin, 23. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. p. 29.
  146. ^ Russell, Dale A. (1989). An Odyssey in Time: Dinosaurs of North America. Minocqua, Wisconsin: NorthWord Press. pp. 64–70. ISBN 978-1-55971-038-1.
  147. ^ Carpenter, Kenneth (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus". In Foster, John R.; Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 131–138.
  148. ^ Chure, Daniel J.; Litwin, Ron; Hasiotis, Stephen T.; Evanoff, Emmett; Carpenter, Kenneth (2006). "The fauna and flora of the Morrison Formation: 2006". In Foster, John R.; Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 233–248.
  149. ^ Dodson, Peter; Behrensmeyer, A.K.; Bakker, Robert T.; McIntosh, John S. (1980). "Taphonomy and paleoecology of the dinosaur beds of the Jurassic Morrison Formation". Paleobiology. 6 (2): 208–232. doi:10.1017/S0094837300025768.
  150. ^ a b Mateus, Octávio (2006). "Jurassic dinosaurs from the Morrison Formation (USA), the Lourinhã and Alcobaça Formations (Portugal), and the Tendaguru Beds (Tanzania): A comparison". In Foster, John R.; Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 223–231.
  151. ^ Chure, Daniel J. (2000). "Prey bone utilization by predatory dinosaurs in the Late Jurassic of North America, with comments on prey bone use by dinosaurs throughout the Mesozoic". Gaia. 15: 227–232. ISSN 0871-5424.
  152. ^ Drumheller, Stephanie K.; McHugh, Julia B.; Kane, Miriam; Riedel, Anja; D’Amore, Domenic C. (27 May 2020). "High frequencies of theropod bite marks provide evidence for feeding, scavenging, and possible cannibalism in a stressed Late Jurassic ecosystem". PLOS ONE. 15 (5): e0233115. Bibcode:2020PLoSO..1533115D. doi:10.1371/journal.pone.0233115. ISSN 1932-6203. PMC 7252595. PMID 32459808.

External links

  •   Media related to Allosaurus at Wikimedia Commons
  • at The Theropod Database
  • Utah State Fossil, Allosaurus 17 June 2010 at the Wayback Machine, from Pioneer: Utah's Online Library
  • and at Scott Hartman's Skeletal Drawing website
  • List of the many possible Allosaurus species... 24 March 2005 at the Wayback Machine
  •   Data related to Allosaurus at Wikispecies
  •   Wikijunior:Dinosaurs/Allosaurus at Wikibooks

June 27, 2023
allosaurus, ɔːr, extinct, genus, large, carnosaurian, theropod, dinosaur, that, lived, million, years, during, late, jurassic, period, kimmeridgian, late, tithonian, ages, name, means, different, lizard, alluding, unique, time, discovery, concave, vertebrae, d. Allosaurus ˌ ae l e ˈ s ɔːr e s 2 3 is an extinct genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period Kimmeridgian to late Tithonian ages The name Allosaurus means different lizard alluding to its unique at the time of its discovery concave vertebrae It is derived from the Greek words ἄllos allos different strange or other and saῦros sauros lizard or reptile The first fossil remains that could definitively be ascribed to this genus were described in 1877 by famed paleontologist Othniel Charles Marsh As one of the first well known theropod dinosaurs it has long attracted attention outside of paleontological circles AllosaurusTemporal range Late Jurassic Kimmeridgian to Tithonian 155 145 Ma PreꞒ Ꞓ O S D C P T J K Pg NA jimmadseni specimen Big Al II SMA 0005 Scientific classificationKingdom AnimaliaPhylum ChordataClade DinosauriaClade SaurischiaClade TheropodaFamily AllosauridaeSubfamily AllosaurinaeMarsh 1878Genus AllosaurusMarsh 1877Type species Allosaurus fragilisMarsh 1877Other species 1 A europaeus Mateus et al 2006 A jimmadseni Chure amp Loewen 2020 A maximus Chure 1995SynonymsList Antrodemus Leidy 1870Apatodon Marsh 1878Creosaurus Marsh 1878Epanterias Cope 1878Labrosaurus Marsh 1879 Madsenius Bakker 1990 Wyomingraptor Bakker 1997Allosaurus was a large bipedal predator for its time Its skull was light robust and equipped with dozens of sharp serrated teeth It averaged 8 5 meters 28 ft in length for A fragilis with the largest specimens estimated as being 9 7 metres 32 ft long Relative to the large and powerful legs its three fingered hands were small and the body was balanced by a long muscular tail It is classified as an allosaurid a type of carnosaurian theropod dinosaur The genus has a very complicated taxonomy and includes at least three 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 known from Portugal It was known for over half of the 20th century as Antrodemus but a study of the abundant 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 most abundant large predator of the Morrison Formation Allosaurus was at the top of the food chain and probably preyed on contemporaneous large herbivorous dinosaurs with the possibility of hunting other predators Potential prey included ornithopods stegosaurids and sauropods Some paleontologists interpret Allosaurus as having had cooperative social behavior and hunting in packs while others believe individuals may have been aggressive toward each other and that congregations of this genus are the result of lone individuals feeding on the same carcasses Contents 1 Discovery and history 1 1 Early discoveries and research 1 2 Cleveland Lloyd discoveries 1 3 Recent work 1980s present 1 3 1 Big Al and Big Al II 1 4 Species 1 5 Synonyms 1 6 Formerly assigned species and fossils 2 Description 2 1 Skull 2 2 Postcranial skeleton 2 3 Skin 3 Classification 4 Paleobiology 4 1 Life history 4 2 Feeding 4 3 Social behavior 4 4 Brain and senses 4 5 Paleopathology 5 Paleoecology 6 References 7 External linksDiscovery and history EditEarly discoveries and research Edit Mounted A fragilis specimen AMNH 5753 posed as scavenging an Apatosaurus AMNH 5753 in a Charles R Knight life restoration The discovery and early study of Allosaurus is complicated by the multiplicity of names coined during the Bone Wars of the late 19th century The first described fossil in this history was a bone obtained secondhand by Ferdinand Vandeveer Hayden in 1869 It came from 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 4 He later decided it deserved its own genus Antrodemus 5 Allosaurus itself is based on 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 Greek words allos allos meaning strange or different and sauros sayros meaning lizard or reptile 6 It was named different lizard because its vertebrae were different from those of other dinosaurs known at the time of its discovery 7 8 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 north of Canon City 7 O C Marsh and Edward Drinker Cope who were in scientific competition with each other 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 9 and Labrosaurus 10 as well as Cope s Epanterias 11 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 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 12 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 it in 1903 several years after Cope had died it was found to be one of the most complete theropod specimens then known and the skeleton now cataloged as AMNH 5753 was put on public view in 1908 13 This is the well known mount poised over a partial Apatosaurus skeleton as if scavenging it illustrated as such in a painting 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 14 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 15 For example Williston pointed out in 1901 that Marsh had never been able to adequately distinguish Allosaurus from Creosaurus 16 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 named Antrodemus by Leidy was indistinguishable from those of Allosaurus and that Antrodemus should be the preferred name because as the older name it had priority 17 Antrodemus became the accepted name for this familiar genus for over 50 years until James Henry 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 18 Antrodemus has been used informally for convenience when distinguishing between the skull Gilmore restored and the composite skull restored by Madsen 19 Cleveland Lloyd discoveries Edit A fragilis at the Cleveland Lloyd Dinosaur Quarry museum Utah Although sporadic work at what became known as the Cleveland Lloyd Dinosaur Quarry in Emery County Utah had taken place as early as 1927 and the fossil site itself described by William L Stokes in 1945 20 major operations did not begin there until 1960 Under a cooperative effort involving nearly 40 institutions thousands of bones were recovered between 1960 and 1965 led by James Henry Madsen 18 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 A fragilis have been found there out of at a minimum 73 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 suggesting numerous mutually exclusive explanations for how it may have formed Suggestions have ranged from animals getting stuck in a bog becoming trapped in deep mud falling victim to drought induced mortality around a waterhole and getting trapped in a spring fed pond or seep 21 Regardless of the actual cause the great quantity of well preserved Allosaurus remains has allowed this genus to be known in great detail making it among the best known of all theropods Skeletal remains from the quarry pertain to individuals of almost all ages and sizes from less than 1 meter 3 3 feet 22 to 12 meters 39 feet long and the disarticulation is an advantage for describing bones usually found fused 18 Due to being one of Utah s two fossil quarries where numerous Allosaurus specimens have been discovered Allosaurus was designated as the state fossil of Utah in 1988 23 Recent work 1980s present Edit The period since Madsen s monograph has been marked by a great expansion in studies dealing with topics concerning Allosaurus in life paleobiological and paleoecological topics Such studies have covered topics including skeletal variation 24 growth 25 26 skull construction 27 hunting methods 28 the brain 29 and the possibility of gregarious living and parental care 30 Reanalysis of old material particularly of large allosaur specimens 31 32 new discoveries in Portugal 33 and several very complete new specimens 34 35 36 have also contributed to the growing knowledge base Big Al and Big Al II Edit Big Al at the Museum of the Rockies In 1991 Big Al MOR 693 a 95 complete partially articulated specimen of Allosaurus was discovered measuring about 8 meters about 26 ft long MOR 693 was excavated near Shell Wyoming by a joint Museum of the Rockies and University of Wyoming Geological Museum team 37 This skeleton was discovered by a Swiss team led by Kirby Siber Chure and Loewen in 2020 identified the individual as a representative of the species Allosaurus jimmadseni In 1996 the same team discovered a second Allosaurus Big Al II This specimen the best preserved skeleton of its kind to date is also referred to Allosaurus jimmadseni 1 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 37 as it was a subadult estimated at only 87 grown 38 The specimen was described by Breithaupt in 1996 35 Nineteen of its bones were broken or showed signs of serious infection which may have contributed to Big Al s death Pathologic bones included five ribs five vertebrae and four bones of the feet Several of its damaged bones showed signs of osteomyelitis a severe 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 Big Al had an infection on the first phalanx on the third toe that was afflicted by an involucrum The infection was long lived perhaps up to six months 38 39 Big Al II is also known to have multiple injuries 40 Species Edit Diagram comparing skulls of the three recognized species A fragilis A A jimmadseni B A europaeus C Six species of Allosaurus have been named A amplus 41 A atrox 42 A europaeus 43 the type species A fragilis 44 A jimmadseni 1 42 and A lucasi 45 Among these 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 1 However A europaeus does not show any unique characters compared to the North American species so a reevaluation of its validity is required 46 47 A fragilis is the type species and was named by Marsh in 1877 7 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 44 Details of the humerus upper arm of A fragilis have been used as diagnostic among Morrison theropods 18 but A jimmadseni indicates that this is no longer the case at the species level 42 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 1 42 48 49 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 22 A fragilis A jimmadseni 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 44 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 31 50 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 51 52 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 53 A europaeus was found in the Kimmeridgian age Porto Novo Member of the Lourinha Formation 43 but it may be the same as A fragilis 46 Allosaurus material from Portugal was first reported in 1999 on the basis of MHNUL AND 001 a partial skeleton including a quadrate vertebrae ribs gastralia chevrons part of the hips and legs This specimen was assigned to A fragilis 33 but the subsequent discovery of a partial skull and neck ML 415 near Lourinha in the Kimmeridgian age Porto Novo Member of the Lourinha Formation spurred the naming of the new species as A europaeus by Octavio Mateus and colleagues The species appeared earlier in the Jurassic than A fragilis and differs from other species of Allosaurus in cranial details 43 However more material may show it to be A fragilis as originally described 46 The issue of species and potential synonyms is complicated by the type specimen of Allosaurus fragilis 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 submitted a petition to the ICZN to have the name A fragilis officially transferred to the more complete specimen USNM4734 as a neotype 54 Synonyms Edit Holotype material of Creosaurus atrox Creosaurus Epanterias and Labrosaurus are regarded as junior synonyms of Allosaurus 44 Most of the species that are regarded as synonyms of A fragilis or that were misassigned to the genus are obscure and based on very 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 55 Later researchers suggested that the bone was pathologic showing an injury to the living animal 17 and that part of the unusual form of the rear of the bone was due to plaster reconstruction 56 It is now regarded as an example of A fragilis 44 Cast of synonym A atrox at the South Australian Museum In his 1988 book Predatory Dinosaurs of the World the freelance artist amp author Gregory S Paul proposed that A fragilis had tall pointed horns and a slender build compared to a postulated second species A atrox as well as not being a different sex due to rarity 31 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 that includes a couple of pieces of the skull portions of nine tail vertebrae two hip vertebrae an ilium and ankle and foot bones 9 Although the idea of two common Morrison allosaur species was followed in some semi technical and popular works 50 the 2000 thesis on Allosauridae noted that Charles Gilmore mistakenly reconstructed USNM 4734 as having a shorter skull than the specimens referred by Paul to atrox refuting supposed differences between USNM 4734 and putative A atrox specimens like DINO 2560 AMNH 600 and AMNH 666 42 Allosaurus agilis seen in Zittel 1887 and Osborn 1912 is a typographical error for A fragilis 42 Allosaurus ferox is a typographical error by Marsh for A fragilis in a figure caption for the partial skull YPM 1893 57 and YPM 1893 has been treated as a specimen of A fragilis 44 Likewise Labrosaurus fragilis is a typographical error by Marsh 1896 for Labrosaurus ferox 56 A whitei is a nomen nudum coined by Pickering in 1996 for the complete Allosaurus specimens that Paul referred to A atrox 42 Madsenius was coined by David Lambert in 1990 58 being based on remains from Dinosaur National Monument assigned to Allosaurus or Creosaurus a synonym of Allosaurus and was to be described by paleontologist Robert Bakker as Madsenius trux 59 However Madsenius is now seen as yet another synonym of Allosaurus because Bakker s action was predicated upon the false assumption of USNM 4734 being distinct from long snouted Allosaurus due to errors in Gilmore s 1920 reconstruction of USNM 4734 60 Wyomingraptor was informally coined by Bakker for allosaurid remains from the Morrison Formation of the Late Jurassic The remains unearthed are labeled as Allosaurus and are housed in the Tate Geological Museum However there has been no official description of the remains and Wyomingraptor has been dismissed as a nomen nudum with the remains referable to Allosaurus 61 62 60 Formerly assigned species and fossils Edit Antrodemus valens holotype tail vertebra above compared to the same of Allosaurus below 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 Arundel Formation of Maryland 63 although most of the remains were removed by Richard Swann Lull to the new ornithopod species Dryosaurus grandis except for a tooth 64 It was transferred to Antrodemus by Oliver Hay in 1902 but Hay later clarified that this was an inexplicable error on his part 65 66 Gilmore considered the tooth nondiagnostic but transferred it to Dryptosaurus as D medius 17 The referral was not accepted in the most recent review of basal tetanurans and Allosaurus medius was simply listed as a dubious species of theropod 44 It may be closely related to Acrocanthosaurus 67 Allosaurus valens is a new combination for Antrodemus valens used by Friedrich von Huene in 1932 42 Antrodemus valens itself may also pertain to Allosaurus fragilis 44 as Gilmore suggested in 1920 17 A lucaris another Marsh name was given to a partial skeleton in 1878 9 He later decided it warranted its own genus Labrosaurus 10 but this has not been accepted and A lucaris is also regarded as another specimen of A fragilis 44 Allosaurus lucaris is known mostly from vertebrae sharing characters with Allosaurus 68 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 undiagnostic and thus A lucaris was a nomen dubium 54 Allosaurus sibiricus was described in 1914 by A N Riabinin on the basis of a bone later identified as a partial fourth metatarsal from the Early Cretaceous of Buryatia Russia 69 It was transferred to Chilantaisaurus in 1990 70 but is now considered a nomen dubium indeterminate beyond Theropoda 71 Allosaurus meriani was a new combination by George Olshevsky for Megalosaurus meriani Greppin 1870 based on a tooth from the Late Jurassic of Switzerland 72 73 However a recent overview of Ceratosaurus included it in Ceratosaurus sp 56 Apatodon mirus based on a scrap of vertebra Marsh first thought to be a mammalian jaw has been listed as a synonym of Allosaurus fragilis 74 75 However it was considered indeterminate beyond Dinosauria by Chure 42 and Mickey Mortimer believes that the synonymy of Apatodon with Allosaurus was due to correspondence to Ralph Molnar by John McIntosh whereby the latter reportedly found a paper saying that Othniel Charles Marsh admitted that the Apatodon holotype was actually an allosaurid dorsal vertebra 76 A amplexus was named by Gregory S Paul for giant Morrison allosaur remains and included in his conception Saurophagus maximus later Saurophaganax 31 A amplexus was originally coined by Cope in 1878 as the type species of his new genus Epanterias 11 and is based on what is now AMNH 5767 parts of three vertebrae a coracoid and a metatarsal 77 Following Paul s work this species has been accepted as a synonym of A fragilis 44 A 2010 study by Paul and Kenneth Carpenter however indicates that Epanterias is temporally younger than the A fragilis type specimen so it is a separate species at minimum 78 A maximus was a new combination by David K Smith for Chure s Saurophaganax maximus a taxon created by Chure in 1995 for giant allosaurid remains from the Morrison of Oklahoma These remains had been known as Saurophagus but that name was already in use leading Chure to propose a substitute 32 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 24 This reassignment was rejected in a review of basal tetanurans 44 There are also several species left over from the synonymizations of Creosaurus and Labrosaurus with Allosaurus Creosaurus potens was named by Lull in 1911 for a vertebra from the Early Cretaceous of Maryland 64 It is now regarded as a dubious theropod 44 Labrosaurus stechowi described in 1920 by Janensch based on isolated Ceratosaurus like teeth from the Tendaguru beds of Tanzania 79 was listed by Donald F Glut as a species of Allosaurus 75 is now considered a dubious ceratosaurian related to Ceratosaurus 56 80 L sulcatus named by Marsh in 1896 for a Morrison theropod tooth 57 which like L stechowi is now regarded as a dubious Ceratosaurus like ceratosaur 56 80 A tendagurensis tibia Naturkunde Museum Berlin A tendagurensis was named in 1925 by Werner Janensch for a partial shin MB R 3620 found in the Kimmeridgian age Tendaguru Formation in Mtwara Tanzania 81 Although tabulated as a tentatively valid species of Allosaurus in the second edition of the Dinosauria 44 subsequent studies place it as indeterminate beyond Tetanurae either a carcharodontosaurian or megalosaurid 82 83 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 84 Kurzanov 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 to them 85 They were reclassified as an indeterminate theropod 71 Also reports of Allosaurus in Shanxi China go back to at least 1982 86 These were interpreted as Torvosaurus remains in 2012 71 An astragalus 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 refugium for animals that had gone extinct elsewhere 87 This identification was challenged by Samuel Welles who thought it more resembled that of an ornithomimid 88 but the original authors defended their identification 89 With fifteen years of new specimens and research to look at Daniel Chure reexamined the bone and found that it was not Allosaurus but could represent an allosauroid 90 Similarly Yoichi Azuma and Phil Currie in their description of Fukuiraptor noted that the bone closely resembled that of their new genus 91 This specimen is sometimes referred to as Allosaurus robustus an informal museum name 48 It likely belonged to something similar to Australovenator 92 although one study considered it to belong to an abelisaur 93 Description Edit 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 slightly sloping tail and reduced forelimbs Allosaurus fragilis the best known species had an average length of 8 5 m 28 ft and mass of 1 7 metric tons 1 9 short tons 75 94 with the largest definitive Allosaurus specimen AMNH 680 estimated at 9 7 meters 32 feet long 84 with an estimated weight of 2 3 2 7 metric tons 2 5 3 0 short tons 84 95 In his 1976 monograph on Allosaurus James H Madsen mentioned a range of bone sizes which he interpreted to show a maximum length of 12 to 13 m 39 to 43 ft 18 As with dinosaurs in general weight estimates are debatable and since 1980 have ranged between 1 5 metric tons 1 7 short tons 1 to 4 metric tons 1 1 to 4 4 short tons and approximately 1 metric ton 1 1 short tons for modal adult weight not maximum 96 John Foster a specialist on the Morrison Formation suggests that 1 metric ton 1 1 short tons is reasonable for large adults of A fragilis but that 700 kg 1 500 lb is a closer estimate for individuals represented by the average sized thigh bones he has measured 97 Using the subadult specimen nicknamed Big Al since assigned to the species Allosaurus jimmadseni 1 researchers using computer modelling arrived at a best estimate of 1 5 metric tons 1 7 short tons for the individual but by varying parameters they found a range from approximately 1 4 metric tons 1 5 short tons to approximately 2 metric tons 2 2 short tons 98 A europaeus has been measured up to 7 m 23 ft in length and 1 metric ton 1 1 short tons in body mass 94 A jimmadseni skeletal reconstruction Several gigantic specimens have been attributed to Allosaurus but may in fact belong to other genera The closely related genus Saurophaganax OMNH 1708 reached perhaps 10 5 m 34 ft in length 94 and its single species has sometimes been included in the genus Allosaurus as Allosaurus maximus though recent studies support it as a separate genus 42 Another potential specimen of Allosaurus once assigned to the genus Epanterias AMNH 5767 may have measured 12 1 meters 40 feet in length 84 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 Saurophaganax 99 David K Smith examining Allosaurus fossils by quarry found that the Cleveland Lloyd Dinosaur Quarry Utah specimens are generally smaller than those from Como Bluff Wyoming or Brigham Young University s Dry Mesa Quarry Colorado but the shapes of the bones themselves did not vary between the sites 51 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 gradational suggesting individual variation was responsible 24 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 astragalus an ankle bone 52 Kenneth Carpenter using 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 horns and the proposed differentiation of A jimmadseni based on the shape of the jugal 53 A study published by Motani et al in 2020 suggests that Allosaurus was also sexually dimorphic in the width of the femur s head against its length 100 Skull Edit A jimmadseni skull with diagram highlighting individual bones The skull and teeth of Allosaurus were modestly proportioned for a theropod of its size Paleontologist Gregory S Paul gives a length of 845 mm 33 3 in for a skull belonging to an individual he estimates at 7 9 m 26 ft long 31 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 14 and 17 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 14 and 17 teeth with an average count of 16 The teeth became shorter narrower 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 18 Its skull was light robust and equipped with dozens of sharp serrated teeth The skull had a pair of horns above and in front of the eyes These horns were composed of extensions of the lacrimal bones 18 and varied in shape and size There were also lower paired ridges running along the top edges of the nasal bones that led into the horns 18 The horns were probably covered in a keratin sheath and may have had a variety of functions including acting as sunshades for the eyes 18 being used for display and being used in combat against other members of the same species 31 101 although they were fragile 18 There was a ridge along the back of the skull roof for muscle attachment as is also seen in tyrannosaurids 31 Inside the lacrimal bones were depressions that may have held glands such as salt glands 12 Within the maxillae were sinuses that were better developed than those of more basal theropods such as Ceratosaurus and Marshosaurus they may have been related to the sense of smell perhaps holding something like Jacobson s organs The roof of the braincase was thin perhaps to improve thermoregulation for the brain 18 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 102 The braincase and frontals may also have had a joint 18 Postcranial skeleton Edit Life restoration of A fragilis Allosaurus had nine vertebrae in the neck 14 in the back and five in the sacrum supporting the hips 103 The number of tail vertebrae is unknown and varied with individual size James Madsen estimated about 50 18 while Gregory S Paul considered that to be too many and suggested 45 or less 31 There were hollow spaces in the neck and anterior back vertebrae 18 Such spaces which are also found in modern theropods that is the birds are interpreted as having held air sacs used in respiration 44 The rib cage was broad giving it a barrel chest especially in comparison to less derived theropods like Ceratosaurus 104 Allosaurus had gastralia belly ribs but these are not common findings 18 and they may have ossified poorly 31 In one published case the gastralia show evidence of injury during life 34 A furcula wishbone was also present but has only been recognized since 1996 in some cases furculae were confused with gastralia 34 105 The ilium the main hip bone was massive and the 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 characteristic with females lacking fused bones to make egg laying easier 18 This proposal has not attracted further attention however Hand and claws of A fragilis The forelimbs of Allosaurus were short in comparison to the hindlimbs only about 35 the length of the hindlimbs in adults 106 and had three fingers per hand tipped with large strongly curved and pointed claws 18 The arms were powerful 31 and the forearm was somewhat shorter than the upper arm 1 1 2 ulna humerus ratio 17 The wrist had a version of the semilunate carpal 107 also found in more derived theropods like maniraptorans Of the three fingers the innermost or thumb was the largest 31 and diverged from the others 17 The phalangeal formula is 2 3 4 0 0 meaning that the innermost finger phalange has two bones the next has three and the third finger has four 108 The legs were not as long or suited for speed as those of tyrannosaurids and the claws of the toes were less developed and more hoof like than those of earlier theropods 31 Each foot had three weight bearing toes and an inner dewclaw which Madsen suggested could have been used for grasping in juveniles 18 There was also what is interpreted as the splint like remnant of a fifth outermost metatarsal perhaps used as a lever between the Achilles tendon and foot 109 Skin Edit Skin impressions from Allosaurus have been described One impression from a juvenile specimen measures 30 cm and is associated with the anterior dorsal ribs pectoral region 110 The impression show small scales measuring 1 3 mm in diameter A large skin impression from the Big Al Two specimen associated with the base of the tail measures 20 cm x 20 cm and show large scales measuring up to 2 cm in diameter However it has been noted that these scales are more similar to those of sauropods and due to the presence of non theropod remains associated with the tail of Big Al Two there is a possibility that this skin impression is not from Allosaurus 110 Another Allosaurus fossil feature a skin impression from the mandible showing scales measuring 1 2 mm in diameter The same fossil also preserves skin impressions from the ventral side of the neck showing broad scutes A small skin impression from an Allosaurus skull has been reported but never described 110 Classification EditAllosaurus was an allosaurid a member of a family of large theropods within the larger group Carnosauria The family name Allosauridae was created for this genus in 1878 by Othniel Charles Marsh 9 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 Gilmore 1920 17 von Huene 1926 111 Romer 1956 and 1966 112 113 Steel 1970 114 and Walker 1964 115 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 116 Acrocanthosaurus Chilantaisaurus Compsosuchus Stokesosaurus and Szechuanosaurus 117 Given modern knowledge of theropod diversity and the advent of cladistic study of evolutionary relationships none of these theropods is now recognized as an allosaurid although several like Acrocanthosaurus and Yangchuanosaurus are members of closely related families 44 Restored skeleton of Saurophaganax or A maximus Illustrations showing the skull of A jimmadseni from the side A top B and back C Below is a cladogram based on the analysis of Benson et al in 2010 118 Allosauroidea SinraptoridaeAllosaurus Neovenator FukuiraptorMegaraptor EocarchariaAcrocanthosaurusShaochilong TyrannotitanCarcharodontosaurus Giganotosaurus Mapusaurus Allosauridae is one of four families in Allosauroidea the other three are Neovenatoridae 118 Carcharodontosauridae and Sinraptoridae 44 Allosauridae has at times been proposed as ancestral to the Tyrannosauridae which would make it paraphyletic one example being Gregory S Paul s Predatory Dinosaurs of the World 119 but this has been rejected with tyrannosaurids identified as members of a separate branch of theropods the Coelurosauria 120 Allosauridae is the smallest of the carnosaur families with only Saurophaganax and a currently unnamed French allosauroid accepted as possible valid genera besides Allosaurus in the most recent review 44 Another genus Epanterias is a potential valid member but it and Saurophaganax may turn out to be large examples of Allosaurus 31 Recent reviews have kept the genus Saurophaganax and included Epanterias with Allosaurus 96 44 Paleobiology EditLife history Edit Skeletons at different growth stages on display the Natural History Museum of Utah 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 eggs crushed eggs from Colorado have been suggested as those of Allosaurus 75 Based on histological analysis of limb bones bone deposition appears to stop at around 22 to 28 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 15 with an estimated growth rate of about 150 kilograms 330 lb per year 25 Medullary bone tissue endosteally derived ephemeral mineralization located inside the medulla of the long bones in gravid female birds has been reported in at least one Allosaurus specimen a shin bone from the Cleveland Lloyd Quarry 121 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 has been used to establish sex and show it had reached reproductive age However other studies have called into question some cases of medullary bone in dinosaurs including this Allosaurus individual Data from extant birds suggested that the medullary bone in this Allosaurus individual may have been the result of a bone pathology instead 122 However with the confirmation of medullary tissue indicating sex in a specimen of Tyrannosaurus it may be possible to ascertain whether or not the Allosaurus in question was indeed female 123 Restoration of a juvenile Allosaurus 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 26 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 124 Conversely the skull bones appear to have generally grown isometrically increasing in size without changing in proportion 53 Feeding Edit Bitten Stegosaurus plate close up showing how well the damage matches the front of an Allosaurus mouth Many paleontologists accept Allosaurus as an active predator of large animals There is dramatic evidence for allosaur attacks on Stegosaurus including an Allosaurus tail vertebra with a partially healed puncture wound that fits a Stegosaurus tail spike and a Stegosaurus neck plate with a U shaped wound that correlates well with an Allosaurus snout 125 Sauropods 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 126 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 31 Another possibility is that it preferred to hunt juveniles instead of fully grown adults 97 50 Research in the 1990s and the first decade of the 21st century may have found other solutions to this question Robert T Bakker comparing Allosaurus to Cenozoic saber 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 saber 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 28 A fragilis showing its maximum possible gape based on Bakker 1998 and Rayfield et al 2001 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 8 724 N 27 127 but the skull could withstand nearly 55 500 N of vertical force against the tooth row 27 The authors suggested that Allosaurus used its skull like a machete 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 27 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 128 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 129 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 44 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 97 This is compatible with other evidence that the forelimbs were strong and capable of restraining prey 107 Studies done by Stephen Lautenschager et al from the University of Bristol also indicate Allosaurus could open its jaws quite wide and sustain considerable muscle force When compared with Tyrannosaurus and the therizinosaurid Erlikosaurus in the same study it was found that Allosaurus had a wider gape than either the animal was capable of opening its jaws to a 92 degree angle at maximum The findings also indicate that large carnivorous dinosaurs like modern carnivores had wider jaw gapes than herbivores 130 131 A biomechanical study published in 2013 by Eric Snively and colleagues found that Allosaurus had an unusually low attachment point on the skull for the longissimus capitis superficialis neck muscle compared to other theropods such as Tyrannosaurus This would have allowed the animal to make rapid and forceful vertical movements with the skull The authors found that vertical strikes as proposed by Bakker and Rayfield are consistent with the animal s capabilities They also found that the animal probably processed carcasses by vertical movements in a similar manner to falcons such as kestrels the animal could have gripped prey with the skull and feet then pulled back and up to remove flesh This differs from the prey handling envisioned for tyrannosaurids which probably tore flesh with lateral shakes of the skull similar to crocodilians 132 In addition Allosaurus was able to move its head and neck around relatively rapidly and with considerable control at the cost of power 133 Allosaurus and Stegosaurus skeletons the Denver Museum of Nature and Science 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 crocodilians As with crocodilians this may have been enough to judge prey distance and time attacks 134 The arms compared with those of other theropods were suited for both grasping prey at a distance or clutching it close 107 and the articulation of the claws suggests that they could have been used to hook things 17 Finally the top speed of Allosaurus has been estimated at 30 to 55 kilometers per hour 19 to 34 miles per hour 135 A paper on the cranio dental morphology of Allosaurus and how it worked has deemed the hatchet jaw attack unlikely reinterpreting the unusually wide gape as an adaptation to allow Allosaurus to deliver a muscle driven bite to large prey with the weaker jaw muscles being a trade off to allow for the widened gape 136 Social behavior Edit The holotype dentary of Labrosaurus ferox which may have been injured by the bite of another A fragilis It has been speculated since the 1970s that Allosaurus preyed on sauropods and other large dinosaurs by hunting in groups 137 Such a depiction is common in semitechnical and popular dinosaur literature 12 116 50 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 lairs for their young to eat until they were grown and prevented other carnivores from scavenging on the food 30 However there is actually little evidence of gregarious behavior in theropods 44 and social interactions with members of the same species would have included antagonistic encounters as shown by injuries to gastralia 34 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 or to settle territorial disputes 138 Although Allosaurus may have hunted in packs 139 it has been argued that Allosaurus and other theropods had largely aggressive interactions instead of cooperative interactions with other members of their own species The study in question noted that cooperative hunting of prey much larger than an individual predator as is commonly inferred for theropod dinosaurs is rare among vertebrates in general and modern diapsid carnivores including lizards crocodiles and birds rarely cooperate to hunt in such a way Instead they are typically territorial and will kill and cannibalize intruders of the same species and will also do the same to smaller individuals that attempt to eat before they do when aggregated at feeding sites According to this interpretation the accumulation of remains of multiple Allosaurus individuals at the same site e g in the Cleveland Lloyd Quarry are not due to pack hunting but to the fact that Allosaurus individuals were drawn together to feed on other disabled or dead allosaurs and were sometimes killed in the process 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 crocodiles and Komodo dragons The same interpretation applies to Bakker s lair sites 140 There is some evidence for cannibalism in Allosaurus including Allosaurus shed teeth found among rib fragments possible tooth marks on a shoulder blade 141 and cannibalized allosaur skeletons among the bones at Bakker s lair sites 142 Brain and senses Edit Endocast cast of the brain cavity of Allosaurus The brain of Allosaurus as interpreted from spiral CT scanning of an endocast was more consistent with crocodilian brains than those of the other living archosaurs birds The structure of the 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 bulbs were large and seem to have been well suited for detecting odors although the area for evaluating smells was relatively small 29 Paleopathology Edit Mounted A fragilis skeleton USNM4734 which has several healed injuries In 2001 Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior Since stress fractures are caused by repeated trauma rather than singular events they are more likely to be caused by the behavior of the animal than other kinds of injury Stress fractures and tendon avulsions occurring in the forelimb have special behavioral significance since while injuries to the feet could be caused by running or migration resistant prey items are the most probable source of injuries to the hand Allosaurus was one of only two theropods examined in the study to exhibit a tendon avulsion and in both cases the avulsion occurred on the forelimb When the researchers looked for stress fractures they found that Allosaurus had a significantly greater number of stress fractures than Albertosaurus Ornithomimus or Archaeornithomimus Of the 47 hand bones the researchers studied three were found to contain stress fractures Of the feet 281 bones were studied and 17 were found to have stress fractures The stress fractures in the foot bones were distributed to the proximal phalanges and occurred across all three weight bearing toes in statistically indistinguishable numbers Since the lower end of the third metatarsal would have contacted the ground first while an allosaur was running it would have borne the most stress If the allosaurs stress fractures were caused by damage accumulating while walking or running this bone should have experience more stress fractures than the others The lack of such a bias in the examined Allosaurus fossils indicates an origin for the stress fractures from a source other than running The authors conclude that these fractures occurred during interaction with prey like an allosaur trying to hold struggling prey with its feet The abundance of stress fractures and avulsion injuries in Allosaurus provide evidence for very active predation based rather than scavenging diets 143 The left scapula and fibula of an Allosaurus fragilis specimen catalogued as USNM 4734 are both pathological both probably due to healed fractures The specimen USNM 8367 preserved several pathological gastralia which preserve evidence of healed fractures near their middle Some of the fractures were poorly healed and formed pseudoarthroses A specimen with a fractured rib was recovered from the Cleveland Lloyd Quarry Another specimen had fractured ribs and fused vertebrae near the end of the tail An apparent subadult male Allosaurus fragilis was reported to have extensive pathologies with a total of fourteen separate injuries The specimen MOR 693 had pathologies on five ribs the sixth neck vertebra the third eighth and thirteenth back vertebrae the second tail vertebra and its chevron the gastralia right scapula manual phalanx I left ilium metatarsals III and V the first phalanx of the third toe and the third phalanx of the second The ilium had a large hole caused by a blow from above The near end of the first phalanx of the third toe was afflicted by an involucrum 144 Skeletal restoration of Big Al II showing bones with pathologies Other pathologies reported in Allosaurus include 122 144 Willow breaks in two ribs Healed fractures in the humerus and radius Distortion of joint surfaces in the foot possibly due to osteoarthritis or developmental issues Osteopetrosis along the endosteal surface of a tibia Distortions of the joint surfaces of the tail vertebrae possibly due to osetoarthritis or developmental issues E xtensive neoplastic ankylosis of caudals possibly due to physical trauma as well as the fusion of chevrons to centra Coossification of vertebral centra near the end of the tail Amputation of a chevron and foot bone both possibly a result of bites E xtensive exostoses in the first phalanx of the third toe Lesions similar to those caused by osteomyelitis in two scapulae Bone spurs in a premaxilla ungual and two metacarpals Exostosis in a pedal phalanx possibly attributable to an infectious disease A metacarpal with a round depressed fracturePaleoecology Edit Restoration of Barosaurus rearing to defend itself against a pair of A fragilis Allosaurus was the most common large theropod in the vast tract of Western American fossil bearing rock known as the Morrison Formation accounting for 70 to 75 of theropod specimens 97 and as such was at the top trophic level of the Morrison food chain 145 The Morrison Formation is interpreted as a semiarid environment with distinct wet and dry seasons and flat floodplains 146 Vegetation varied from river lining forests of conifers tree ferns and ferns gallery forests to fern savannas with occasional trees such as the Araucaria like conifer Brachyphyllum 147 Locations in the Morrison Formation yellow where Allosaurus remains have been found The Morrison Formation has been a rich fossil hunting ground The flora of the period has been revealed by fossils of green algae fungi mosses horsetails ferns cycads ginkgoes and several families of conifers Animal fossils discovered include bivalves snails ray finned fishes frogs salamanders turtles sphenodonts lizards terrestrial and aquatic crocodylomorphs several species of pterosaur numerous dinosaur species and early mammals such as docodonts multituberculates symmetrodonts and triconodonts Dinosaurs known from the Morrison include the theropods Ceratosaurus Ornitholestes Tanycolagreus and Torvosaurus the sauropods Haplocanthosaurus Camarasaurus Cathetosaurus Brachiosaurus Suuwassea Apatosaurus Brontosaurus Barosaurus Diplodocus Supersaurus Amphicoelias and Maraapunisaurus and the ornithischians Camptosaurus Dryosaurus and Stegosaurus 148 Allosaurus is commonly found at the same sites as Apatosaurus Camarasaurus Diplodocus and Stegosaurus 149 The Late Jurassic formations of Portugal where Allosaurus is present are interpreted as having been similar to the Morrison but with a stronger 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 Stegosaurus or have a close counterpart Brachiosaurus and Lusotitan Camptosaurus and Draconyx 150 Dry season at the Mygatt Moore Quarry showing Ceratosaurus center and Allosaurus fighting over the desiccated carcass of another theropod Allosaurus coexisted with fellow large theropods Ceratosaurus and Torvosaurus in both the United States and Portugal 150 The three appear to have had different ecological niches based on anatomy and the location of fossils Ceratosaurus and Torvosaurus 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 Allosaurus was more compact with longer legs faster but less maneuverable and seems to have preferred dry floodplains 142 Ceratosaurus better known than Torvosaurus differed noticeably from Allosaurus in functional anatomy by having a taller narrower skull with large broad teeth 19 Allosaurus was itself a potential food item to other carnivores as illustrated by an Allosaurus 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 151 A bone assemblage in the Upper Jurassic Mygatt Moore Quarry preserves an unusually high occurrence of theropod bite marks most of which can be attributed to Allosaurus and Ceratosaurus while others could have been made by Saurophaganax or Torvosaurus given the size of the striations While the position of the bite marks on the herbivorous dinosaurs is consistent with predation or early access to remains bite marks found on Allosaurus material suggest scavenging either from the other theropods or from another Allosaurus The unusually high concentration of theropod bite marks compared to other assemblages could be explained either by a more complete utilization of resources during a dry season by theropods or by a collecting bias in other localities 152 References Edit a b c d e f Chure D J Loewen M A 2020 Cranial anatomy of Allosaurus jimmadseni a new species from the lower part of the Morrison Formation Upper Jurassic of Western North America PeerJ 8 e7803 doi 10 7717 peerj 7803 PMC 6984342 PMID 32002317 Allosaurus Merriam Webster Dictionary Allosaurus Dictionary com Unabridged Online n d Leidy Joseph 1870 Remarks on Poicilopleuron valens Clidastes intermedius Leiodon proriger Baptemys wyomingensis and Emys stevensonianus Proceedings of the Academy of Natural Sciences of Philadelphia 22 3 4 Leidy Joseph 1873 Contribution to the extinct vertebrate fauna of the western territories Report of the U S Geological Survey of the Territories I 14 358 Liddell amp Scott 1980 Greek English Lexicon Abridged Edition Oxford Oxford University Press ISBN 978 0 19 910207 5 OCLC 17396377 a b c Marsh Othniel Charles 1877 Notice of new dinosaurian reptiles from the Jurassic formation American Journal of Science and Arts 14 84 514 516 Bibcode 1877AmJS 14 514M doi 10 2475 ajs s3 14 84 514 S2CID 130488291 Creisler Ben 7 July 2003 Dinosauria Translation and Pronunciation Guide A Dinosauria On Line Archived from the original on 5 January 2010 Retrieved 11 September 2007 a b c d Marsh Othniel Charles 1878 Notice of new dinosaurian reptiles American Journal of Science and Arts 15 87 241 244 Bibcode 1878AmJS 15 241M doi 10 2475 ajs s3 15 87 241 S2CID 131371457 a b Marsh Othniel Charles 1879 Principal characters of American Jurassic dinosaurs Part II American Journal of Science Series 3 17 97 86 92 doi 10 2475 ajs s3 17 97 86 hdl 2027 hvd 32044107172876 S2CID 219247096 a b Cope Edward Drinker 1878 A new opisthocoelous dinosaur American Naturalist 12 6 406 408 doi 10 1086 272127 a b c Norman David B 1985 Carnosaurs The Illustrated Encyclopedia of Dinosaurs An Original and Compelling Insight into Life in the Dinosaur Kingdom New York Crescent Books pp 62 67 ISBN 978 0 517 46890 6 Norell Mark A Gaffney Eric S Dingus Lowell 1995 Discovering Dinosaurs in the American Museum of Natural History New York Knopf pp 112 113 ISBN 978 0 679 43386 6 Breithaupt Brent H 1999 AMNH 5753 The world s first free standing theropod skeleton Journal of Vertebrate Paleontology 19 3 Suppl 33A doi 10 1080 02724634 1999 10011202 Williston Samuel Wendell 1878 American Jurassic dinosaurs Transactions of the Kansas Academy of Science 6 42 46 doi 10 2307 3623553 JSTOR 3623553 Williston Samuel Wendell 1901 The dinosaurian genus Creosaurus Marsh American Journal of Science Series 4 11 62 111 114 Bibcode 1901AmJS 11 111W doi 10 2475 ajs s4 11 62 111 a b c d e f g h Gilmore Charles W 1920 Osteology of the carnivorous dinosauria in the United States National Museum with special reference to the genera Antrodemus Allosaurus and Ceratosaurus PDF Bulletin of the United States National Museum 110 1 159 doi 10 5479 si 03629236 110 i hdl 2027 uiug 30112032536010 Archived PDF from the original on 9 October 2022 a b c d e f g h i j k l m n o p q r Madsen James H Jr 1993 1976 Allosaurus fragilis A Revised Osteology Utah Geological Survey Bulletin 109 2nd ed Salt Lake City Utah Geological Survey a b Henderson Donald M 1998 Skull and tooth morphology as indicators of niche partitioning in sympatric Morrison Formation theropods Gaia 15 219 266 Stokes William L 1945 A new quarry for Jurassic dinosaurs Science 101 2614 115 117 Bibcode 1945Sci 101 115S doi 10 1126 science 101 2614 115 a PMID 17799203 S2CID 13589884 Hunt Adrian P Lucas Spencer G Krainer Karl Spielmann Justin 2006 The taphonomy of the Cleveland Lloyd Dinosaur Quarry Upper Jurassic Morrison Formation Utah a re evaluation In Foster John R Lucas Spencer G eds Paleontology and Geology of the Upper Jurassic Morrison Formation New Mexico Museum of Natural History and Science Bulletin 36 Albuquerque New Mexico New Mexico Museum of Natural History and Science pp 57 65 a b Loewen Mark A Sampson Scott D Carrano Matthew T Chure Daniel J 2003 Morphology taxonomy and stratigraphy of Allosaurus from the Upper Jurassic Morrison Formation Journal of Vertebrate Paleontology 23 3 72A doi 10 1080 02724634 2003 10010538 S2CID 220410105 Utah Symbols State Fossil Pioneer Utah s Online Library State of Utah Archived from the original on 8 January 2010 Retrieved 16 June 2010 a b c Smith David K 1998 A morphometric analysis of Allosaurus Journal of Vertebrate Paleontology 18 1 126 142 Bibcode 1998JVPal 18 126S doi 10 1080 02724634 1998 10011039 a b Bybee Paul J Lee AH Lamm ET 2006 Sizing the Jurassic theropod dinosaur Allosaurus Assessing growth strategy and evolution of ontogenetic scaling of limbs Journal of Morphology 267 3 347 359 doi 10 1002 jmor 10406 PMID 16380967 S2CID 35111050 a b Foster John R Chure Daniel J 2006 Hindlimb allometry in the Late Jurassic theropod dinosaur Allosaurus with comments on its abundance and distribution In Foster John R Lucas Spencer G eds Paleontology and Geology of the Upper Jurassic Morrison Formation New Mexico Museum of Natural History and Science Bulletin 36 Albuquerque New Mexico New Mexico Museum of Natural History and Science pp 119 122 a b c d Rayfield Emily J Norman DB Horner CC Horner JR Smith PM Thomason JJ Upchurch P 2001 Cranial design and function in a large theropod dinosaur Nature 409 6823 1033 1037 Bibcode 2001Natur 409 1033R doi 10 1038 35059070 PMID 11234010 S2CID 4396729 a b Bakker Robert T 1998 Brontosaur killers Late Jurassic allosaurids as sabre tooth cat analogues Gaia 15 145 158 ISSN 0871 5424 a b Rogers Scott W 1999 Allosaurus crocodiles and birds Evolutionary clues from spiral computed tomography of an endocast The Anatomical Record 257 5 163 173 doi 10 1002 SICI 1097 0185 19991015 257 5 lt 162 AID AR5 gt 3 0 CO 2 W PMID 10597341 a b Bakker Robert T 1997 Raptor Family values Allosaur parents brought giant carcasses into their lair to feed their young In Wolberg Donald L Sump Edmund Rosenberg Gary D eds Dinofest International Proceedings of a Symposium Held at Arizona State University Philadelphia Academy of Natural Sciences pp 51 63 ISBN 978 0 935868 94 4 a b c d e f g h i j k l m n Paul Gregory S 1988 Genus Allosaurus Predatory Dinosaurs of the World New York Simon amp Schuster pp 307 313 ISBN 978 0 671 61946 6 a b Chure Daniel J 1995 A reassessment of the gigantic theropod Saurophagus maximus from the Morrison Formation Upper Jurassic of Oklahoma USA In Ailing Sun Yuangqing Wang eds Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota Short Papers Beijing China Ocean Press pp 103 106 ISBN 978 7 5027 3898 3 a b Perez Moreno B P Chure D J Pires C Marques Da Silva C Dos Santos V Dantas P Povoas L Cachao M Sanz J L 1999 On the presence of Allosaurus fragilis Theropoda Carnosauria in the Upper Jurassic of Portugal First evidence of an intercontinental dinosaur species PDF Journal of the Geological Society 156 3 449 452 Bibcode 1999JGSoc 156 449P doi 10 1144 gsjgs 156 3 0449 S2CID 130952546 Archived from the original PDF on 25 October 2007 a b c d Chure Daniel J 2000 Observations on the morphology and pathology of the gastral basket of Allosaurus based on a new specimen from Dinosaur National Monument Oryctos 3 29 37 ISSN 1290 4805 a b Breithaupt Brent 1996 The discovery of a nearly complete Allosaurus from the Jurassic Morrison Formation eastern Bighorn Basin Wyoming In Brown C E Kirkwood S C Miller T S eds Forty Seventh Annual Field Conference Guidebook Casper Wyoming Wyoming Geological Association pp 309 313 OCLC 36004754 Howe Dinosaur Quarry Wyoming s Jurassic Treasure GeoScience Adventures 24 July 2007 Archived from the original on 3 December 2007 Retrieved 27 September 2007 a b Breithaupt Brent H The case of Big Al the Allosaurus a study in paleodetective partnerships Archived from the original on 7 January 2010 Retrieved 3 October 2007 a b Hanna Rebecca R 2002 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 of Vertebrate Paleontology 22 1 76 90 doi 10 1671 0272 4634 2002 022 0076 MIAIIA 2 0 CO 2 ISSN 0272 4634 S2CID 85654858 Wilkin Jack 24 November 2019 Review of Pathologies on MOR 693 An Allosaurus from the Late Jurassic of Wyoming and Implications for Understanding Allosaur Immune Systems PaleorXiv doi 10 31233 osf io f3rh6 S2CID 242466868 Foth C Evers S Pabst B Mateus O Flisch A Patthey M Rauhut O W M 2015 New insights into the lifestyle of Allosaurus Dinosauria Theropoda based on another specimen with multiple pathologies PeerJ 3 e824v1 doi 10 7717 peerj 940 PMC 4435507 PMID 26020001 Galton Peter M Carpenter Kenneth Dalman Sebastian G 2015 The holotype pes of the Morrison dinosaur Camptonotus amplus Marsh 1879 Upper Jurassic western USA is it Camptosaurus Sauropoda or Allosaurus Neues Jahrbuch fur Geologie und Palaontologie Abhandlungen 275 3 317 335 doi 10 1127 njgpa 2015 0467 a b c d e f g h i j Chure Daniel J 2000 A new species ofAllosaurusfrom the Morrison Formation of Dinosaur National Monument Utah Colorado and a revision of the theropod family Allosauridae PhD dissertation Columbia University a b c Mateus Octavio Walen Aart Antunes Miguel Telles 2006 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 In Foster John R Lucas Spencer G eds Paleontology and Geology of the Upper Jurassic Morrison Formation New Mexico Museum of Natural History and Science Bulletin 36 Albuquerque New Mexico New Mexico Museum of Natural History and Science pp 123 129 a b c d e f g h i j k l m n o p q r s t Holtz Thomas R Jr Molnar Ralph E Currie Philip J 2004 Basal Tetanurae In Weishampel David B Dodson Peter Osmolska Halszka eds The Dinosauria 2nd ed Berkeley University of California Press pp 71 110 ISBN 978 0 520 24209 8 Dalman Sebastian G 2014 Osteology of a large allosauroid theropod from the Upper Jurassic Tithonian Morrison Formation of Colorado USA Volumina Jurassica 12 2 159 180 a b c Malafaia Elisabete Dantas Pedro Ortega Francisco Escaso Fernando 2007 Nuevos restos de Allosaurus fragilis Theropoda Carnosauria del yacimiento de Andres Jurasico Superior centro oeste de Portugal New remains of Allosaurus fragilis Theropoda Carnosauria of the Andres deposit Upper Jurassic central west Portugal PDF Cantera Paleontologica in Spanish and English 255 271 Archived PDF from the original on 9 October 2022 Evers Serjoscha W Foth Christian Rauhut Oliver W M 7 February 2020 Notes on the cheek region of the Late Jurassic theropod dinosaur Allosaurus PeerJ 8 e8493 doi 10 7717 peerj 8493 ISSN 2167 8359 PMC 7008823 PMID 32076581 a b Glut Donald F 2003 Allosaurus Dinosaurs The Encyclopedia 3rd Supplement Jefferson North Carolina McFarland amp Co pp 221 233 ISBN 978 0 7864 1166 5 New species of Allosaurus discovered in Utah phys org a b c d Lessem Don Glut Donald F 1993 Allosaurus The Dinosaur Society s Dinosaur Encyclopedia Random House pp 19 20 ISBN 978 0 679 41770 5 OCLC 30361459 a b Smith David K 1996 A discriminant analysis of Allosaurus population using quarries as the operational units Museum of Northern Arizona Bulletin 60 69 72 a b Smith David K 1999 Patterns of size related variation within Allosaurus Journal of Vertebrate Paleontology 19 2 402 403 Bibcode 1999JVPal 19 402S doi 10 1080 02724634 1999 10011153 a b c Carpenter Kenneth 2010 Variation in a population of Theropoda Dinosauria Allosaurus from the Cleveland Lloyd Quarry Upper Jurassic Utah USA Paleontological Research 14 4 250 259 doi 10 2517 1342 8144 14 4 250 S2CID 84635714 a b Paul Gregory S Carpenter Kenneth 2010 Allosaurus Marsh 1877 Dinosauria Theropoda proposed conservation of usage by designation of a neotype for its type species Allosaurus fragilis Marsh 1877 Bulletin of Zoological Nomenclature 67 1 53 56 doi 10 21805 bzn v67i1 a7 S2CID 81735811 Marsh Othniel Charles 1884 Principal characters of American Jurassic dinosaurs Part VIII American Journal of Science Series 3 27 160 329 340 Bibcode 1884AmJS 27 329M doi 10 2475 ajs s3 27 160 329 S2CID 131076004 a b c d e Madsen James H Welles Samuel P 2000 Ceratosaurus Dinosauria Theropoda a Revised Osteology Miscellaneous Publication 00 2 Utah Geological Survey a b Marsh Othniel Charles 1896 The dinosaurs of North America United States Geological Survey 16th Annual Report 1894 95 55 133 244 MADSENIUS dinoruss com 27 March 2006 Archived from the original on 27 June 2008 Retrieved 18 December 2020 Lambert D 1990 The Dinosaur Data Book Facts on File Oxford England 320 pp a b Carnosauria www theropoddatabase com Retrieved 18 December 2020 Bakker 1997 Raptor family values Allosaur parents brought great carcasses into their lair to feed their young In Wolberg Sump and Rosenberg eds Dinofest International Proceedings of a Symposium Academy of Natural Sciences 51 63 Re Raptor question dml cmnh org Archived from the original on 24 June 2021 Retrieved 1 January 2019 Marsh Othniel Charles 1888 Notice of a new genus of Sauropoda and other new dinosaurs from the Potomac Formation American Journal of Science Series 3 35 205 89 94 Bibcode 1888AmJS 35 89M doi 10 2475 ajs s3 35 205 89 S2CID 130879860 a b Lull Richard Swann 1911 The Reptilia of the Arundel Formation Maryland Geological Survey Lower Cretaceous 173 178 Hay Oliver Perry 1902 Bibliography and catalogue of the fossil vertebrata of North America Bulletin doi 10 3133 b179 Hay Oliver Perry 1908 On certain genera and species of carnivorous dinosaurs with special reference to Ceratosaurus nasicornis Marsh Proceedings of the United States National Museum 35 1648 351 366 doi 10 5479 si 00963801 35 1648 351 hdl 10088 14046 Neotheropoda The Theropod Database Retrieved 28 September 2018 Marsh O C 1878 Notice of new dinosaurian reptiles PDF American Journal of Science 15 87 241 244 Bibcode 1878AmJS 15 241M doi 10 2475 ajs s3 15 87 241 S2CID 131371457 Archived PDF from the original on 9 October 2022 Riabinin Anatoly Nikolaenvich 1914 Zamtka o dinozavry ise Zabaykalya Trudy Geologichyeskago Muszeyah Imeni Petra Velikago Imperatorskoy Academiy Nauk in Russian 8 5 133 140 Molnar Ralph E Kurzanov Sergei M Dong Zhiming 1990 Carnosauria In Weishampel David B Dodson Peter Osmolska Halszka eds The Dinosauria 1st ed Berkeley University of California Press pp 169 209 ISBN 978 0 520 06727 1 a b c Carrano Benson Sampson 2012 The phylogeny of Tetanurae Dinosauria Theropoda Journal of Systematic Palaeontology 10 2 211 300 doi 10 1080 14772019 2011 630927 S2CID 85354215 Greppin J B 1870 Description geologique du Jura bernois et de quelques districts adjacents Beitrage zur Geologischen Karte der Schweiz in French 8 1 357 Olshevsky 1978 The archosaurian taxa excluding the Crocodylia Mesozoic Meanderings 1 1 50 Olshevsky G 1991 A revision of the parainfraclass Archosauria Cope 1869 excluding the advanced Crocodylia Mesozoic Meanderings 2 196 pp a b c d Glut Donald F 1997 Allosaurus Dinosaurs The Encyclopedia Jefferson North Carolina McFarland amp Co pp 105 117 ISBN 978 0 89950 917 4 Apatodonmirus The Theropod Database Retrieved 28 September 2018 Osborn Henry Fairfield Mook Charles C 1921 Camarasaurus Amphicoelias and other sauropods of Cope Memoirs of the American Museum of Natural History New Series 3 1 247 387 Bibcode 1919GSAB 30 379O doi 10 1130 GSAB 30 379 hdl 2027 mdp 39015042532476 Paul G S Carpenter K 2010 Case 3506 Allosaurus Marsh 1877 Dinosauria Theropoda proposed conservation of usage by designation of a neotype for its type species Allosaurus fragilis Marsh 1877 PDF Bulletin of Zoological Nomenclature 67 1 53 56 doi 10 21805 bzn v67i1 a7 S2CID 81735811 Janensch Werner 1920 Uber Elaphrosaurus bambergi und die Megalosaurier aus den Tendaguru Schichten Deutsch Ostafricas Sitzungsberichte Gesellschaft Naturforschender Freunde Berlin 8 225 235 a b Tykoski Ronald S and Rowe Timothy 2004 Ceratosauria in The Dinosauria 2nd 47 70 Janensch Werner 1925 Die Coelurosaurier und Theropoden der Tendaguru Schichten Deutsch Ostafrikas Palaeontographica in German 1 Suppl 7 1 99 Rauhut Oliver W M 2005 Post cranial remains of coelurosaurs Dinosauria Theropoda from the Late Jurassic of Tanzania Geological Magazine 142 1 97 107 Bibcode 2005GeoM 142 97R doi 10 1017 S0016756804000330 S2CID 131517482 Rauhut Oliver W M Theropod dinosaurs from the Late Jurassic of Tendaguru Tanzania Special Papers in Palaeontology 86 195 239 a b c d Mortimer Mickey 21 July 2003 And the largest Theropod is The Dinosaur Mailing List Archived from the original on 25 March 2010 Retrieved 8 September 2007 Kurzanov Sergei S Efimov Mikhail B Gubin Yuri M 2003 New archosaurs from the Jurassic of Siberia and Mongolia Paleontological Journal 37 1 53 57 Glut Donald F 1982 The New Dinosaur Dictionary Secaucus NJ Citadel Press p 44 ISBN 978 0 8065 0782 8 Molnar Ralph E Flannery Timothy F Rich Thomas H V 1981 An allosaurid theropod dinosaur from the Early Cretaceous of Victoria Australia Alcheringa 5 2 141 146 doi 10 1080 03115518108565427 Welles Samuel P 1983 Allosaurus Saurischia Theropoda not yet in Australia Journal of Paleontology 57 2 196 Molnar Ralph E Flannery Timothy F Rich Thomas H V 1985 Aussie Allosaurus after all Journal of Paleontology 59 6 1511 1535 Chure Daniel J 1998 A reassessment of the Australian Allosaurus and its implications for the Australian refugium concept Journal of Vertebrate Paleontology 18 3 Suppl 1 94 doi 10 1080 02724634 1998 10011116 Azuma Yoichi Currie Philip J 2000 A new carnosaur Dinosauria Theropoda from the Lower Cretaceous of Japan PDF Journal of Vertebrate Paleontology 37 12 1735 1753 Bibcode 2000CaJES 37 1735A doi 10 1139 e00 064 Hocknull Scott A White Matt A Tischler Travis R Cook Alex G Calleja Naomi D Sloan Trish Elliott David A 2009 Sereno Paul ed New Mid Cretaceous Latest Albian Dinosaurs from Winton Queensland Australia PLOS ONE 4 7 e6190 Bibcode 2009PLoSO 4 6190H doi 10 1371 journal pone 0006190 PMC 2703565 PMID 19584929 Agnolin F L Ezcurra M D Pais D F Salisbury S W 2010 A reappraisal of the Cretaceous non avian dinosaur faunas from Australia and New Zealand Evidence for their Gondwanan affinities PDF Journal of Systematic Palaeontology 8 2 257 300 doi 10 1080 14772011003594870 S2CID 130568551 Archived PDF from the original on 9 October 2022 a b c Paul Gregory S 2010 The Princeton Field Guide to Dinosaurs Princeton University Press pp 94 96 Campione N E Evans D C Brown C M Carrano M T 2014 Body mass estimation in non avian bipeds using a theoretical conversion to quadruped stylopodial proportions Methods in Ecology and Evolution 5 9 913 923 doi 10 1111 2041 210X 12226 hdl 10088 25281 a b Foster John R 2003 Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation Upper Jurassic Rocky Mountain Region U S A New Mexico Museum of Natural History and Science Bulletin 23 Albuquerque New Mexico Museum of Natural History and Science p 37 a b c d Foster John 2007 Allosaurus fragilis Jurassic West The Dinosaurs of the Morrison Formation and Their World Bloomington Indiana Indiana University Press pp 170 176 ISBN 978 0 253 34870 8 OCLC 77830875 Bates Karl T Falkingham Peter L Breithaupt Brent H Hodgetts David Sellers William I Manning Phillip L 2009 How big was Big Al Quantifying the effect of soft tissue and osteological unknowns on mass predictions for Allosaurus Dinosauria Theropoda Palaeontologia Electronica 12 3 unpaginated Archived from the original on 25 December 2009 Retrieved 13 December 2009 Foster John 2007 Jurassic West the Dinosaurs of the Morrison Formation and Their World Bloomington Indiana Indiana University Press p 117 Motani Ryosuke 2021 Sex estimation from morphology in living animals and dinosaurs Zoological Journal of the Linnean Society 192 4 1029 1044 doi 10 1093 zoolinnean zlaa181 via academic oup com Molnar Ralph E 1977 Analogies in the evolution of combat and display structures in ornithopods and ungulates Evolutionary Theory 3 165 190 Paul Gregory S 1988 Predatory Dinosaurs of the World 91 and Figure 4 5 93 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 10 neck and 13 back vertebrae Paul Gregory S 1988 Predatory Dinosaurs of the World 277 Chure Daniel J Madsen James 1996 On the presence of furculae in some non maniraptoran theropods Journal of Vertebrate Paleontology 16 3 573 577 Bibcode 1996JVPal 16 573C doi 10 1080 02724634 1996 10011341 Middleton Kevin M 2000 Theropod forelimb design and evolution PDF Zoological Journal of the Linnean Society 128 2 149 187 doi 10 1006 zjls 1998 0193 Archived from the original PDF on 25 October 2007 Retrieved 25 October 2007 a b c Carpenter Kenneth 2002 Forelimb biomechanics of nonavian theropod dinosaurs in predation Senckenbergiana Lethaea 82 1 59 76 doi 10 1007 BF03043773 S2CID 84702973 Martin A J 2006 Introduction to the Study of Dinosaurs Second Edition Oxford Blackwell Publishing 560 pp ISBN 1 4051 3413 5 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 a b c Hendrickx Christophe Bell Phil R Pittman Michael Milner Andrew R C Cuesta Elena O Connor Jingmai Loewen Mark Currie Philip J Mateus Octavio Kaye Thomas G Delcourt Rafael June 2022 Morphology and distribution of scales dermal ossifications and other non feather integumentary structures in non avialan theropod dinosaurs Biological Reviews 97 3 960 1004 doi 10 1111 brv 12829 ISSN 1464 7931 PMID 34991180 S2CID 245820672 von Huene Friedrich 1926 The carnivorous Saurischia in the Jura and Cretaceous formations principally in Europe Revista del Museo de La Plata 29 35 167 Romer Alfred S 1956 Osteology of the Reptiles Chicago University of Chicago Press ISBN 978 0 89464 985 1 Romer Alfred S 1966 Vertebrate Paleontology Third ed Chicago University of Chicago Press ISBN 978 0 7167 1822 2 Steel R 1970 Part 14 Saurischia Handbuch der Palaoherpetologie Encyclopedia of Paleoherpetology Gustav Fischer Verlag Stuttgart 1 87 Walker Alick D 1964 Triassic reptiles from the Elgin area Ornithosuchus and the origin of carnosaurs Philosophical Transactions of the Royal Society B 248 744 53 134 Bibcode 1964RSPTB 248 53W doi 10 1098 rstb 1964 0009 JSTOR 2416617 S2CID 86378219 a b Lambert David the Diagram Group 1983 Allosaurids A Field Guide to Dinosaurs New York Avon Books pp 80 81 ISBN 978 0 380 83519 5 Lambert David the Diagram Group 1990 Allosaurids The Dinosaur Data Book New York Avon Books p 130 ISBN 978 0 380 75896 8 a b Benson R B J Carrano M T Brusatte S L 2010 A new clade of archaic large bodied predatory dinosaurs Theropoda Allosauroidea that survived to the latest Mesozoic PDF Naturwissenschaften 97 1 71 78 Bibcode 2010NW 97 71B doi 10 1007 s00114 009 0614 x PMID 19826771 S2CID 22646156 Paul Gregory S 1988 The allosaur tyrannosaur group Predatory Dinosaurs of the World 301 347 Holtz Thomas R Jr 1994 The phylogenetic position of the Tyrannosauridae Implications for theropod systematics Journal of Paleontology 68 5 1100 1117 Bibcode 1994JPal 68 1100H doi 10 1017 S0022336000026706 JSTOR 1306180 S2CID 129684676 Lee Andrew H Werning S 2008 Sexual maturity in growing dinosaurs does not fit reptilian growth models Proceedings of the National Academy of Sciences of the United States of America 105 2 582 587 Bibcode 2008PNAS 105 582L doi 10 1073 pnas 0708903105 PMC 2206579 PMID 18195356 a b Chinsamy A Tumarkin Deratzian A 2009 Pathological Bone Tissues in a Turkey Vulture and a Nonavian Dinosaur Implications for Interpreting Endosteal Bone and Radial Fibrolamellar Bone in Fossil Dinosaurs Anat Rec 292 9 1478 1484 doi 10 1002 ar 20991 PMID 19711479 S2CID 41596233 Pregnant T rex could aid in dino sex typing Science Daily 15 March 2016 Archived from the original on 14 April 2016 Loewen Mark A 2002 Ontogenetic changes in hindlimb musculature and function in the Late Jurassic theropod Allosaurus Journal of Vertebrate Paleontology 22 3 Suppl 80A Carpenter Kenneth Sanders Frank McWhinney Lorrie A Wood Lowell 2005 Evidence for predator prey relationships Examples for Allosaurus and Stegosaurus In Carpenter Kenneth ed The Carnivorous Dinosaurs Bloomington and Indianapolis Indiana University Press pp 325 350 ISBN 978 0 253 34539 4 Fastovsky David E and Smith Joshua B 2004 Dinosaur Paleoecology in The Dinosauria 2nd ed 614 626 Bates K T Falkingham P L 29 February 2012 Estimating maximum bite performance in Tyrannosaurus rex using multi body dynamics Biological Letters 8 4 660 664 doi 10 1098 rsbl 2012 0056 PMC 3391458 PMID 22378742 Frazzetta T H Kardong K V 2002 Prey attack by a large theropod dinosaur Nature 416 6879 387 388 Bibcode 2002Natur 416 387F doi 10 1038 416387a PMID 11919619 S2CID 4388901 Rayfield Emily J Norman D B Upchurch P 2002 Prey attack by a large theropod dinosaur Response to Frazzetta and Kardong 2002 Nature 416 6879 388 Bibcode 2002Natur 416 388R doi 10 1038 416388a S2CID 4392259 Lautenschlager Stephan 4 November 2015 Estimating cranial musculoskeletal constraints in theropod dinosaurs Royal Society Open Science 2 11 150495 Bibcode 2015RSOS 250495L doi 10 1098 rsos 150495 PMC 4680622 PMID 26716007 Better to eat you with How dinosaurs jaws influenced diet Science Daily 3 November 2015 Archived from the original on 7 March 2016 Snively Eric Cotton John R Ridgely Ryan Witmer Lawrence M 2013 Multibody dynamics model of head and neck function in Allosaurus Dinosauria Theropoda Palaeontologia Electronica 16 2 doi 10 26879 338 Ohio University 22 May 2013 Allosaurus fed more like a falcon than a crocodile Engineering anatomy work reveals differences in dinosaur feeding styles ScienceDaily Retrieved 22 May 2013 Stevens Kent A 2006 Binocular vision in theropod dinosaurs Journal of Vertebrate Paleontology 26 2 321 330 doi 10 1671 0272 4634 2006 26 321 BVITD 2 0 CO 2 ISSN 0272 4634 S2CID 85694979 Christiansen Per 1998 Strength indicator values of theropod long bones with comments on limb proportions and cursorial potential Gaia 15 241 255 ISSN 0871 5424 Anton M Sanchez I Salesa Manuel Turner A 2003 The muscle powered bite of Allosaurus Dinosauria Theropoda An interpretation of cranio dental morphology PDF Estudios Geologicos 59 5 313 323 doi 10 3989 egeol 03595 6106 Archived PDF from the original on 9 October 2022 Farlow James O 1976 Speculations about the diet and foraging behavior of large carnivorous dinosaurs American Midland Naturalist 95 1 186 191 doi 10 2307 2424244 JSTOR 2424244 Tanke Darren H 1998 Head biting behavior in theropod dinosaurs Paleopathological evidence Gaia 15 167 184 Currie Philip J 1999 Theropods In Farlow James Brett Surman M K eds The Complete Dinosaur Indiana Indiana University Press p 228 ISBN 978 0 253 21313 6 Roach Brian T Brinkman Daniel L 2007 A reevaluation of cooperative pack hunting and gregariousness in Deinonychus antirrhopus and other nonavian theropod dinosaurs Bulletin of the Peabody Museum of Natural History 48 1 103 138 doi 10 3374 0079 032X 2007 48 103 AROCPH 2 0 CO 2 S2CID 84175628 Goodchild Drake Brandon 2004 A new specimen of Allosaurus from north central Wyoming Journal of Vertebrate Paleontology 24 3 Suppl 65A doi 10 1080 02724634 2004 10010643 S2CID 220415208 a b Bakker Robert T Bir Gary 2004 Dinosaur crime scene investigations theropod behavior at Como Bluff Wyoming and the evolution of birdness In Currie Philip J Koppelhus Eva B Shugar Martin A Wright Joanna L eds Feathered Dragons Studies on the Transition from Dinosaurs to Birds Bloomington and Indianapolis Indiana University Press pp 301 342 ISBN 978 0 253 34373 4 Rothschild B Tanke D H and Ford T L 2001 Theropod stress fractures and tendon avulsions as a clue to activity In Mesozoic Vertebrate Life edited by Tanke D H and Carpenter K Indiana University Press p 331 336 a b Molnar R E 2001 Theropod paleopathology a literature survey In Tanke D H Carpenter K eds Mesozoic Vertebrate Life Indiana University Press pp 337 363 Foster John R 2003 Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation Upper Jurassic Rocky Mountain Region U S A New Mexico Museum of Natural History and Science Bulletin 23 Albuquerque New Mexico New Mexico Museum of Natural History and Science p 29 Russell Dale A 1989 An Odyssey in Time Dinosaurs of North America Minocqua Wisconsin NorthWord Press pp 64 70 ISBN 978 1 55971 038 1 Carpenter Kenneth 2006 Biggest of the big a critical re evaluation of the mega sauropod Amphicoelias fragillimus In Foster John R Lucas Spencer G eds Paleontology and Geology of the Upper Jurassic Morrison Formation New Mexico Museum of Natural History and Science Bulletin 36 Albuquerque New Mexico New Mexico Museum of Natural History and Science pp 131 138 Chure Daniel J Litwin Ron Hasiotis Stephen T Evanoff Emmett Carpenter Kenneth 2006 The fauna and flora of the Morrison Formation 2006 In Foster John R Lucas Spencer G eds Paleontology and Geology of the Upper Jurassic Morrison Formation New Mexico Museum of Natural History and Science Bulletin 36 Albuquerque New Mexico New Mexico Museum of Natural History and Science pp 233 248 Dodson Peter Behrensmeyer A K Bakker Robert T McIntosh John S 1980 Taphonomy and paleoecology of the dinosaur beds of the Jurassic Morrison Formation Paleobiology 6 2 208 232 doi 10 1017 S0094837300025768 a b Mateus Octavio 2006 Jurassic dinosaurs from the Morrison Formation USA the Lourinha and Alcobaca Formations Portugal and the Tendaguru Beds Tanzania A comparison In Foster John R Lucas Spencer G eds Paleontology and Geology of the Upper Jurassic Morrison Formation New Mexico Museum of Natural History and Science Bulletin 36 Albuquerque New Mexico New Mexico Museum of Natural History and Science pp 223 231 Chure Daniel J 2000 Prey bone utilization by predatory dinosaurs in the Late Jurassic of North America with comments on prey bone use by dinosaurs throughout the Mesozoic Gaia 15 227 232 ISSN 0871 5424 Drumheller Stephanie K McHugh Julia B Kane Miriam Riedel Anja D Amore Domenic C 27 May 2020 High frequencies of theropod bite marks provide evidence for feeding scavenging and possible cannibalism in a stressed Late Jurassic ecosystem PLOS ONE 15 5 e0233115 Bibcode 2020PLoSO 1533115D doi 10 1371 journal pone 0233115 ISSN 1932 6203 PMC 7252595 PMID 32459808 External links Edit Media related to Allosaurus at Wikimedia Commons Specimens discussion and references pertaining to Allosaurus fragilis at The Theropod Database Utah State Fossil Allosaurus Archived 17 June 2010 at the Wayback Machine from Pioneer Utah s Online Library Restoration of MOR 693 Big Al and muscle and organ restoration at Scott Hartman s Skeletal Drawing website List of the many possible Allosaurus species Archived 24 March 2005 at the Wayback Machine Data related to Allosaurus at Wikispecies Wikijunior Dinosaurs Allosaurus at Wikibooks Retrieved from https en wikipedia org w index php title Allosaurus amp oldid 1160745962, wikipedia, wiki, book, books, library,

article

, read, download, free, free download, mp3, video, mp4, 3gp, jpg, jpeg, gif, png, picture, music, song, movie, book, game, games.