Allosaurus fact file

The name of this animal means different lizard. Marsh was very famous since he also provided the description of Brontosaurus. When Allosaurus wanted to walk, they used two legs. The skull of this animal was very large. Allosaurus balanced the body and head because it had heavy and long tail.

Get facts about Albertosaurus here. Morrison Formation is a famous discovery place of Allosaurus fossils. This formation is situated in western United States. It is characterized with a sedimentary rock. Even though the legs were long, their arms were shorts. Each hand had three fingers. The tip of the finger featured the curved and sharp caw. Can you guess the length of Allosaurus?

In average, it was 28 feet or 8. The weight of Allosaurus was around 2. Allosaurus just like other types of dinosaurs is a meat eater. They were the active predators which hunted for food. They had sharp teeth which could crash the prey at once.

Allosaurus is seen in various popular books, movies, and documentaries. One of them is in the famous book, The Lost World. It was written by Arthur Conan Doyle in The infection was long lived, perhaps up to 6 months. Big Al Two is also known to have multiple injuries.

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. 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 kilograms lbs per year. 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. 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.

However, with the confirmation of medullary tissue indicating gender in a specimen of Tyrannosaurus , it may be possible to ascertain whether or not the Allosaurus in question was indeed female. 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.

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. Conversely, the skull bones appear to have generally grown isometrically, increasing in size without changing in proportion. 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.

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. However, as Gregory Paul noted in , 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.

Another possibility is that it preferred to hunt juveniles instead of fully grown adults. Research in the s and first decade of the 21st century may have found other solutions to this question. Robert T.

Bakker, comparing Allosaurus to Cenozoic sabre-toothed carnivorous mammals, found similar adaptations, such as a reduction of jaw muscles and increase in neck muscles, and the ability to open the jaws extremely wide.

Although Allosaurus did not have sabre teeth, Bakker suggested another mode of attack that would have used such neck and jaw adaptations: the short teeth in effect became small serrations on a saw-like cutting edge running the length of the upper jaw, which would have been driven into prey. This type of jaw would permit slashing attacks against much larger prey, with the goal of weakening the victim. Planet Dinosaur's description of an Allosaurus speculative hunting behaviore towards a Camptosaurus.

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 to 2, N, less than the values for alligators 13, N , lions 4, N , and leopards 2, N , but the skull could withstand nearly 55, N of vertical force against the tooth row. The authors suggested that Allosaurus used its skull like a hatchet against prey, attacking open-mouthed, slashing flesh with its teeth, and tearing it away without splintering bones, unlike Tyrannosaurus , which is thought to have been capable of damaging bones.

They also suggested that the architecture of the skull could have permitted the use of different strategies against different prey; the skull was light enough to allow attacks on smaller and more agile ornithopods, but strong enough for high-impact ambush attacks against larger prey like stegosaurids and sauropods.

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. 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.

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.

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.

This is compatible with other evidence that the forelimbs were strong and capable of restraining prey. Studies done by Stephen Lautenschager et al. 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 79 degree angle.

The findings also indicate that large carnivorous dinosaurs, like modern carnivores, had wider jaw gapes than herbivores. Allosaurus attacking, based on the theories of Bakker and Rayfield et al. A biomechanical study published in 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. In addition, Allosaurus was able to "move its head and neck around relatively rapidly and with considerable control", at the cost of power.

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

A new study on the skull of Allosaurus and how it worked has deemed the hatchet jaw attack unlikely since the animal would be wasting great amounts of energy with each bite. It seems more likely that Allosaurus hunted prey like any typical carnosaur by ripping great chunks of flesh from the animal and letting it bleed to death. It has been speculated since the s that Allosaurus preyed on sauropods and other large dinosaurs by hunting in groups.

Such a depiction is common in semitechnical and popular dinosaur literature. 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.

However, there is actually little evidence of gregarious behavior in theropods, and social interactions with members of the same species would have included antagonistic encounters, as shown by injuries to gastralia 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. The holotype dentary of Labrosaurus ferox , which may have been injured by the bite of another A. Although Allosaurus may have hunted in packs, 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.

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. There is some evidence for cannibalism in Allosaurus , including Allosaurus shed teeth found among rib fragments, possible tooth marks on a shoulder blade, and cannibalized allosaur skeletons among the bones at Bakker's lair sites.

Further publishments have been aired about potential cannibalism of Allosaurus; however the cases are suspected to be scavenging the dead specimens instead of active cannibalism [1]. 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.

In , 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, 3 were found to contain stress fractures.

Of the feet, bones were studied and 17 found to have stress fractures. The stress fractures in the foot bones "were distributed to the proximalphalanges" 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. The left scapula and fibula of an Allosaurus fragilis specimen catalogued as USNM are both pathological, both probably due to healed fractures. The specimen USNM preserved several pathological gastralia which preserve evidence of healed fractures near their middle.

Some of the fractures were poorly healed and "formed pseudoarthroses. 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 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 probably caused by a blow from above". The near end of the first phalanx of the third toe was afflicted by an involucrum.

Other pathologies reported in Allosaurus include: 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. Coossification of vertebral centra near the end of the tail.

Amputation of a chevron and foot bone, both possibly a result of bites. 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. Restoration of Barosaurus rearing to defend itself against a pair of Allosaurus. The Morrison Formation is interpreted as a semiarid environment with distinct wet and dry seasons, and flat floodplains.

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. 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 crocodylomorphans, 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 Apatosaurus , Brachiosaurus , Brontosaurus , Camarasaurus , and Diplodocus , and the ornithischians Camptosaurus , Dryosaurus , and Stegosaurus.

Allosaurus is commonly found at the same sites as Apatosaurus , Camarasaurus , Diplodocus , and Stegosaurus. 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.

Locations in the Morrison Formation yellow where Allosaurus remains have been found. Allosaurus coexisted with fellow large theropods Ceratosaurus and Torvosaurus in both the United States and Portugal. The three appear to have had different ecological niches, based on anatomy and the location of fossils.

Ceratosaurs and torvosaurs may have preferred to be active around waterways, and had lower, thinner bodies that would have given them an advantage in forest and underbrush terrains, whereas allosaurs were more compact, with longer legs, faster but less maneuverable, and seem to have preferred dry floodplains. Ceratosaurus , better known than Torvosaurus , differed noticeably from Allosaurus in functional anatomy by having a taller, narrower skull with large, broad teeth.

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.

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