Allosaurus ‭(‬Different lizard‭)

Short Info

Allosaurus ‭(‬Different lizard‭)

Phonetic : Al-loh-sore-us.

Named By : Othniel Charles Marsh‭ ‬-‭ ‬1877

Diet : Carnivore

Size : Estimated 8.5 meters long, some specimens up to 12 meter long

Type of Dinosaur : Large Theropod

Type Species : A.‭ ‬fragilis‭ (‬type‭), A.‭ ‬europaeus, A. jimmadseni‬

Found in : USA,‭ ‬Portugal,‭ ‬possibly Tanzania

When it Lived : Late Jurassic, 156-144 million years ago

Allosaurus (/,ael@’so:r@sThe Allosaurus (/,ael@’so:r@s) is the genus belonging to the huge carnosaurian theropod dinosaurs, which lived from between 155 and 145 million years in the Late Jurassic epoch (Kimmeridgian to late Tithonian. Names like “Allosaurus” means “different lizard” referring to its distinctive (at the date when it was discovered) cone-shaped vertebrae. The word comes by its original Greek”allos” (allos) (“different different, different”) as well as sauros (sauros) (“lizard common reptile”). The first fossils that could be definitively assigned to this particular genus was discovered in 1877 , by the paleontologist Othniel Charles Marsh. Being one of the first known theropod dinosaurs, it has for a long time been a subject of interest outside of paleontological circles.

Allosaurus was a massive bipedal predator. Its skull was small robust, strong and was equipped with a plethora of sharp serrated teeth. It was 8.5 meters (28 feet) long, but evidence from fragments suggests it may be as high as 12 meters (39 feet). In comparison to the massive and strong hindlimbs, its three-fingered forelimbs were tinier and its body was supported with a lengthy and muscular tail. The allosaurid is classified an ancestor of carnosaurian theropod dinosaur.

The genus is a complex taxonomy that includes three species that are valid, the most popular among them is A. fragilis. The majority of the remains of Allosaurus are out of the North American Morrison Formation, with material as well as material from Portugal. This was known to the public for more than two-thirds in the early 20th century under Antrodemus however a thorough examination of the abundant remains from the Cleveland-Lloyd Dinosaur quarry brought it’s term “Allosaurus” back to prominence and made it one of the most well-known dinosaurs.

As the largest large predator of the Morrison Formation, Allosaurus was at the highest in the food chain possibly preying upon large herbivorous dinosaurs, and possibly other predators. Possible prey include ornithopods sauropods, and stegosaurids. Certain paleontologists believe that Allosaurus was having been a social animal that was cooperative and hunting in groups however others believe that the individuals might have been hostile towards one another, and that the occurrences of this genus were due to lone animals eating identical carcasses.


CM Allosaurus
WehaveaTrex, CC BY-SA 4.0, via Wikimedia Commons

Allosaurus was a common theropod that had a massive skull with a neck that was short with a long, slight sloped tail, and a diminution of forelimbs. Allosaurus fragilis, the most well-known species has an estimated length of 8.5 meters (28 feet) The largest specimen known as the definitive Allosaurus sample (AMNH 680) was estimated to be 9.7 metres (32 feet) longand an approximate weight of 2.3 meters (2.5 shorter tons). In his monograph of 1976 about Allosaurus, James H. Madsen described a range of bone sizes , which was interpreted by him to indicate an average length of 12-13 meters (39 to 43 feet). Similar to dinosaurs generally the weight estimates are disputed and have since 1980 been ranging from 1,500 to 1,300 kilograms (3,300 pounds) between 1,000 and 4,000 kg (2,200 to 8,800 lbs) as well as 1,010 kg (2,230 pounds) for the modal adult weight (not the maximum). John Foster, a specialist in Morrison Formation, a specialist on Morrison Formation, suggests that 1,000 kilograms (2,200 pounds) is a reasonable weight for adults who weigh a lot from A. fragilis however, he believes 700 kilograms (1,500 pounds) is a more accurate estimate for the individuals represented by the average-sized thigh bones that he has observed. Utilizing the subadult specimen known as “Big Al”, since was assigned to the species Allosaurus Jimmadseni, researchers employing computer models came up with an estimation of 1,500 kilograms (3,300 pounds) for the person however, by using different parameters they came up with a range of around 1,400 kilograms (3,100 lbs) up to around 2,000 kg (4,400 pounds).

Many massive specimens have been linked to Allosaurus but could actually belong to different genera. The closely similar Genus Saurophaganax (OMNH 1708) may have reached 10.9 meters (36 feet) in length. its species alone has occasionally been classified within the group known as Allosaurus to be called Allosaurus maximus, however recent research suggests it is an individual species of genus. Another possible Allosaurus specimen was once designated to the Genus Epanterias (AMNH 567) could have been 12.1 metres (40 feet) in length. Another recent find is a fragment of a Skeleton found in the Peterson Quarry located in the Morrison rocks in New Mexico; this large allosaurid is likely to be another member of Saurophaganax.

David K. Smith, studying Allosaurus fossils in quarrying and found it that Cleveland-Lloyd Dinosaur Quarry (Utah) samples are typically smaller than those of Como Bluff (Wyoming) or Brigham Young University’s Dry Mesa Quarry (Colorado) However, the forms of the bones did not differ between locations. Another study conducted by Smith included Garden Park (Colorado) and Dinosaur National Monument (Utah) specimens did not provide any reason for the existence of multiple species based upon skull variations; this was the most frequent and gradual, suggesting that individual variation was the cause. The study of size-related variation also found no significant variations, however it was evident that the Dry Mesa material tended to form a clump because of the astragalus, which is an ankle bone. Kenneth Carpenter, using skull components from the Cleveland-Lloyd Site has found a wide variety of individuals, challenging the previous distinctions between species due to such factors like the shape of horns, as well as the proposed distinction of A. Jimmadseni on the basis of its shape. Jugal. A study by Motani and co. in the year 2020, suggests the possibility that Allosaurus could also be sexually diverse.

The early discovery and study of Allosaurus is complicated by the multitude of names that were coined in the Bone Wars of the late 19th century. The first fossil that was described in this story was a second-hand bone collected from Ferdinand Vandeveer Hayden in 1869. It was discovered in Middle Park, near Granby, Colorado, probably from Morrison Formation rocks. Locals have identified these fossils to be “petrified horse hoofs”. Hayden sent the piece for examination by Joseph Leidy, who identified it as a portion from a vertebra at the end of its tail and then classified it into the European dinosaur Genus Poekilopleuron as Poicilopleuron valens. Then, he decided that it was worthy of its own genus: Antrodemus.

Allosaurus is actually an adaptation of YPM 1930, which is a tiny collection of bones that were fragmentary, including the vertebrae of three vertebrae. the rib teeth, an toe bone, and, for future discussions an humerus shaft on the left (upper arm). Othniel Charles Marsh was the one who gave the remains the formal name of Allosaurus fragilis in 1877. Allosaurus is derived directly from Greek allos/allos which means “strange” or “different” and sauros/sauros meaning “lizard” or “reptile”. It was named “different lizard because its vertebrae were distinct from the vertebrae of other dinosaurs discovered in the period of discovery. The epithet of the species fragilis is Latin meaning “fragile”, referring to characteristics of the vertebrae that lighten. The bones were retrieved from the Morrison Formation of Garden Park located to the north in Canon City. Marsh along with Edward Drinker Cope, who were competing in the field of science with one another they came up with numerous other genera that were that were based on similar material , which would later be included into the classification of Allosaurus. They include Marsh’s Creosaurus and Labrosaurus and Cope’s Epanterias.

In their rush, Cope and Marsh did not always pursue their discoveries (or in the case of those made by subordinates). For instance, after the discovery made by Benjamin Mudge of the type specimen of Allosaurus in Colorado, Marsh elected to concentrate his work on Wyoming and when work was resumed in Garden Park in 1883, M. P. Felch discovered an nearly complete Allosaurus as well as a few skeletons that were partially preserved. Additionally one of Cope’s collectors, H. F. Hubbell discovered a fossil within the Como Bluff area of Wyoming in 1879. However, he did not acknowledge its fullness or its completeness, and Cope did not take it out of the box. After unpacking it at the end of the year 1903 (several times after Cope had passed away) it was found to be among the most complete of theropod specimens ever discovered, and in 1908 the skeleton which is now categorized by the name of AMNH 5753, came in the public domain. It’s the famous mount positioned over an incomplete Apatosaurus skull, as if to scavenge it, and illustrated in this manner by Charles R. Knight. Though it is notable as the first mount that is freestanding of an theropod dinosaur and frequently depicted and photographed however, it was never scientifically described.

The plethora of names used in the early days made it difficult to conduct further research, and the problem exacerbated by the concise descriptions given in the works of Marsh as well as Cope. In the early days some authors like Samuel Wendell Williston suggested that numerous names had been created. For instance, Williston pointed out in 1901 that Marsh was unable to discern between Allosaurus and Creosaurus. One of the most significant early attempts to clarify the confusing issue was made by Charles W. Gilmore in 1920. He concluded that the vertebra in which we have the tail called Antrodemus by Leidy was not distinguishable from the tail vertebra of Allosaurus and that Antrodemus should be the name of choice since, being the more prestigious name, it had precedence. Antrodemus was adopted as the standard name for this genus that was well-known for more than 50 years till James Madsen published on the Cleveland-Lloyd fossils and found that Allosaurus should be used since Antrodemus was constructed from materials that had weak diagnostic characteristics and information about the locality (for example, the exact geological origin of the single bone of the Antrodemus was derived from is not known). “Antrodemus” has been used to make it easier to distinguish among the skulls of Gilmore has restored as well as the skull composite which was made by Madsen.

Allosaurus atrox Cleveland-Lloyd Quarry
James St. John, CC BY 2.0, via Wikimedia Commons

While sporadic activities on what would later be known as Cleveland-Lloyd Dinosaur Quarry located in Emery County, Utah, was in place in 1927 and the site was mentioned in the work of William L. Stokes in 1945, significant work were not completed until 1960. Through a collaborative effort that involved more than 40 institutions hundreds of bones were found between 1960 between 1960 and 1965. The quarry is noted because of the high proportion in Allosaurus bones, as well as the state of the fossils as well as the absence of any scientific understanding as to the process that led to it being. The majority of bones belong the massive Theropod Allosaurus fragilis (it is believed there are the remains of 46 A. fragilis are found in the quarry from the minimum 73 dinosaurs) The fossils that have been found are well-mixed and disarticulated. More than a dozen research papers have been published about the taphonomy at the site, indicating a variety of distinct explanations of how it came to be. There are a variety of theories, from animals becoming stuck in a bog getting stuck in deep mud to being a victim of the effects of drought around the waterhole, or being stuck in a pond that is fed by a spring or leakage. No matter the cause the abundance of preserved Allosaurus remains enabled this genus to become well-known in depth which makes it one of the most well-known theropods. The remains of the quarry belong to people from all sizes and ages of less than 1 meters (3.3 feet) to 12 meters (39 feet) in length. Furthermore, the disarticulation provides an advantage in describing bones that are commonly together. Because it is one of the two fossil quarries in Utah in which numerous Allosaurus fossils have been found, Allosaurus was designated as the state fossil of Utah in 1988.

In the year 1991, “Big Al” (MOR 693) was a 95 100% complete, partially articulated piece of Allosaurus was found. It measured around eight meters (about 26 feet) long. MOR 693 was found close to Shell, Wyoming, by an unison Museum of the Rockies and University of Wyoming Geological Museum team. The skeleton was discovered by an Swiss team led by Kirby Siber. Chure and Loewen in the year 2020 identified the specimen as an exemplar for the species Allosaurus Jimmadseni. In 1996 the same team found another Allosaurus, “Big Al II”. This is the best preserved skeleton up to now, is called Allosaurus Jimmadseni.

The completeness, conservation, and importance to science of this skeleton has given “Big Al” its name The specimen itself was smaller than the norm for Allosaurus fragilis and was considered a subadult to be only 87% mature. The specimen was first described by Breithaupt in the year 1996. 19 of the bones were fractured or displayed evidence of infection. This could have been a factor in “Big Al’s” death. The pathologic bones comprised five vertebrae, five ribs and four bones of the feet. A number of fractured bones were exhibiting osteomyelitis. which is a bone-related infection. The main issue for the animal living in the wild was an trauma and infection in the foot of the right which likely affected the movement of the foot and could have predisposed the opposite foot to injury as a result of the change in walking. Al was suffering from an infection of the phalanx of the third toe. It was caused due to an involucrum. The infection lasted for a long time possibly as long as six months. Big Al Two is also well-known to have numerous injuries.

Source: Wikipedia