Allosaurus
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Allosaurus (pronounced /ˈæl.əʊˌsɔː.ɹəs/),was a large carnivorous dinosaur up to 12 m (39 ft) long. It was named different lizard' because its vertebrae were different from those of all other dinosaurs. The name comes from the Greek allos/αλλος, meaning 'strange' or 'different' and saurus/σαυρος, meaning 'lizard' or 'reptile'. It was the most common large predator in what is now North America, 155 to 145 million years ago, in the Jurassic Period. More scant finds in North America and Austrailia, from the Early Cretaceous look like Allosaurus, albeit a smaller species. It is quite likely that this versatile hunter did indeed survive the mass extinction 144 MYA.
Allosaurus is the official state fossil of Utah, in the United States.
Description
Allosaurus was a typical large theropod, having a massive skull on a short neck, a long tail and reduced forelimbs. Its most distinctive feature was a pair of blunt horns, just above and in front of the eyes. Although short in comparison to the hindlimbs, the forelimbs were massive and bore large, eagle-like claws. The skull showed evidence of being composed of separate modules, which could be moved in relation to one another, allowing large pieces of meat to be swallowed. The skeleton of Allosaurus, like other theropods, displayed bird-like features, such as a 'wishbone' and neck vertebrae hollowed by air sacs. It is thought that Allosaurus might have hunted in packs, allowing it to bring down the large sauropods of the time. Allosaurus was extremely light compared to other dinosaurs its size, which may have allowed it to leap onto its prey (something that one would expect only small dinosaurs could do) without sustaining severe injury.
Finds
Allosaurus is the most common theropod in the vast tract of dinosaur-bearing rock in the American Southwest known as the Morrison Formation. Remains have been recovered in Montana, Wyoming, South Dakota, Colorado, Oklahoma, New Mexico and Utah, in the United States. There have also been finds in Portugal. Allosaurus shared the Jurassic landscape with several other theropods, including Ceratosaurus and the massive Torvosaurus.
A famous fossil bed can be found in the Cleveland Lloyd Dinosaur Quarry in Utah. This fossil bed contains over 10,000 bones, mostly of Allosaurus, intermixed with the remains of other dinosaurs, such as Stegosaurus and Ceratosaurus. It is still a mystery how the remnants of so many animals can be found in one place. The ratio of fossils of carnivorous animals over fossils of plant eaters is normally very small. Findings like these can be explained by pack hunting, although this is difficult to prove. Another possibility is that the Cleveland Lloyd site formed a 'predator trap', similar to the La Brea Tar Pits, that caused large numbers of predators to become mired in an inescapable sediment [link].
\"Big Al\"
One of the more significant finds was the 1991 discovery of "Big Al" (MOR 593), a 95% complete, partially articulated, juvenile specimen that measured 8 meters (26 feet) in length. Nineteen bones were broken or showed signs of infection, which probably contributed to Big Al's death. It was featured in "The Ballad of Big Al", a special programme in the BBC's Walking with Dinosaurs series. The fossils were excavated near Shell, Wyoming by the Museum of the Rockies and the University of Wyoming Geological Museum. This skeleton was initially discovered by a Swiss team, led by Kirby Siber. The same team later excavated a second Allosaurus, "Big Al Two", which is the best preserved skeleton of its kind to date.Classification and history
The first Allosaurus fossil to be described was a 'petrified horse hoof' given to Ferdinand Vandiveer Hayden in 1869, by the natives of Middle Park, near Granby, Colorado. It was actually a caudal vertebra (a tail bone), which Joseph Leidy tentatively assigned first to the Poekilopleuron genus and later to a new genus, Antrodemus. However, it was Othniel Charles Marsh who gave the formal name Allosaurus fragilis to the genus and type species in 1877, based on much better material, including a partial skeleton, from Garden Park, north of Canon City, Colorado.The species epithet fragilis is Latin for 'fragile'. Both refer to lightening features in the vertebrae.
It is unclear how many species of Allosaurus there were. The material from the Cleveland Lloyd Dinosaur Quarry specimen is much smaller and more lightly-built than the huge and robust Allosaurus from Brigham Young University's Dry Mesa Quarry. Fossils resembling Allosaurus have been described from Portugal.
Allosaurid relatives
- Fukuiraptor is an early Cretaceous therapod from Japan thought to be an Allosaurid.
- An allosaurid astragalus (ankle bone) was found at Cape Patterson, Victoria in easrly Cretaceous beds in Southeastern Australia. This is notable as this part of Australia lay within the Antarctic Circle at the time.
Popular Culture
Along with Tyrannosaurus, Allosaurus has come to represent the quintissential carnivorous dinosaur in popular culture. Allosaurus has featured in the following films:
The Lost World (1925 film) (not to be confused with Tyrannosaurus)
The Valley of Gwangi (Gwangi is technically meant to be an Allosaurus but Ray Harryhausen based his model for the creature off a Tyrannosaurus. Harryhausen often confuses the two, stating in a DVD interview "They're both meat eaters, they're both Tyrants... one was just a bit larger than the other.")
Planet of the Dinosaurs
The main hero of Dinosaucers, "Allo", is an evolved Allosaurus.
Arosaurer, a Mecha from the Zoids franchise, is based on an Allosaurus.
Fran Sinclair of Dinosaurs (TV series) is mentioned on the show and a number of merchandise packaging as being an Allosaurus.
An Allosaurus named Santo was the main character of an Age of Reptiles comic, The Hunt. He was pitted against a pack of Ceratosaurus.
There are unsubstantiated rumors across the Internet that an Allosaurus may be featured in the upcoming film Jurassic Park IV.
Calvin in the comic strip Calvin and Hobbes often imagines himself as an Allosaurus in his "dinosaur" fantasies.
It appears in the second and fith episodes of Walking with Dinosaurs, as the main enemy of Diplodocus, in the second episode. One even injures the main character, a female, by taking a deep bite out of her back. A dwarf species appears in the fith episode, as the main predator of Leaellynasaura, killing and eating the leading Leaellynasaura.
The Walking With Dinosaurs special The Ballad Of Big Al chornicles the life of Big Al.
Allosaurus appears in the PlayStation game Dino Crisis 2.
Allosaurus appear in When Dinosaurs Roamed America, killing a Ceratosaurus and feasting on a wounded Apatosaurus.
References
External links
- [Allosaurus]. DinoData.
- [Allosaurus, the story of "Big Al"], from the University of Wyoming Geological Museum in Laramie.
- [Public Pioneer, Utah State Fossil, Allosaurus], from Utah.gov.
- [Allosaurus fragilis], Smithsonian National Museum of Natural History, Department of Paleobiology.
- [List of the many possible Allosaurus species...]
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