The Allosaurus is a large carnivorous dinosaur which lived in the late Jurassic Period. It is one of the most famous and best-studied dinosaurs currently known.
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Allosaurus is one of the most famous and best-studied dinosaurs currently known to science. Its name means "different lizard", alluding to its unique (at the time of its discovery) concave vertebrae. Growing to an average of 8.5 meters (28 feet), nearly 10 meters (33 feet) in the largest specimens and weighing up to two or three tons, it was one of the most formidable and common predators of the late Jurassic 155-145 million years ago. Fossils of Allosaurus have been discovered in North America and Portugal, showcasing how widespread it was. Three species of Allosaurus are considered valid; Allosaurus fragilis, Allosaurus jimmadseni, and Allosaurus europaeus. Allosaurus had two noticeable crests above and in front of its eyes, which were probably for species recognition and attracting mates. Allosaurus is a member of the Carnosauria, a group of large predatory dinosaurs that include the larger and later Giganotosaurus and Carcharodontosaurus, and more recently has been shown to include the Megalosaurs and Spinosaurs.
Like with Tyrannosaurus rex, it was once assumed in the 19th and early 20th centuries that Allosaurus walked in a kangaroo-like posture with a dragging tail, but is now known that the dinosaur walked with its tail straight out behind it and its back level with the ground. Another error made long ago was that it was once thought to be related to Tyrannosaurus, but it is now known that Tyrannosaurus and Allosaurus are from two different families of dinosaurs: Allosaurus is a carnosaur, while Tyrannosaurus is a Coelurosaur, a member of a superfamily of dinosaurs that includes Velociraptor as another notable member.
Allosaurus was first discovered in 1869, and described by the famous paleontologist Edward Drinker Cope. Since his initial description, hundreds of specimens of Allosaurus have been found in the late Jurassic fossil beds of the Morrison Formation, which runs from Colorado into Wyoming, Utah, Montana, Kansas, Texas, New Mexico, Arizona, Idaho, North and South Dakota, Oklahoma, and Nebraska. In Europe, Allosaurus has been found in the Lourinha Formation of Portugal. During the late Jurassic, Portugal was a large island close to North America, close enough to have similar animals. One of the best assortments of specimens of Allosaurus anywhere in the world comes from the Cleveland-LLoyd Quarry in Dinosaur National Monument, where the remains of more than 44 Allosaurus have been unearthed. Initially believed to be a predator trap akin to the La Brea tar pits of California, the quarry is now believed by some to have been a watering hole where dinosaurs may have died and were scavenged by hungry Allosaurus, which themselves may have died of disease and harsh conditions after drinking the stagnant, dirty water. This theory is itself supported by the fact that many of the Allosaurus are juveniles, but cannot yet be completely proven or disproven.
Two of the three species of Allosaurus lived alongside many other famous dinosaurs in the Morrison Formation of North America. There were many herbivores, which consisted of famous animals such as Stegosaurus and is relative Hesperosaurus, the sauropods Brachiosaurus, Diplodocus, Apatosaurus and its close cousin Brontosaurus, Barosaurus, Supersaurus, Amphicoelias, Maraapunisaurus, and Haplocanthosaurus, the ornithopods Dryosaurus, Nanosaurus, Fruitadens and Camptosaurus, and ankylosaurs like Mymoorapelta and Gargoyleosaurus. Carnivores that shared the environment with Allosaurus in America included Ceratosaurus, small coelurosaurs such as Coelurus and Tanycolagreus, the small tyrannosaur Stokesosaurus, Fosterovenator, and the megalosaurs Marshosaurus and Torvosaurus.
Because of the vast numbers of specimens recovered from Allosaurus, much is known about its life history, behavior, and habits. Allosaurus were apparently similar in lifespan to the later Tyrannosaurus rex, living upwards of 30 years. Juveniles grew quite rapidly, reaching adulthood in about 15 years. In at least one specimen, medullary tissue has been found, suggesting the Allosaurus it belonged to was a female, as medullary tissue is only found in pregnant birds and dinosaurs. Little is known about the nesting habits of Allosaurus, but crushed eggshells from Colorado have been attributed to them. Young Allosaurus were apparently faster than adults, and may have hunted smaller, faster prey until they grew to adulthood, when they would focus on larger animals.
The razor-sharp teeth of Allosaurus were best suited for slicing flesh, and biomechanics studies show it was built to take rapid, snapping bites and slice meat rather than crushing bone. Its bite was weaker than a modern lion's, but it could open its jaws more than 90 degrees to take larger bites out of prey. Like sharks, it may have dashed in, taken a bite to wound its victim, and retreated to let its victim weaken from blood loss before attacking again. Similar studies show it also fed like eagles and falcons, using its powerful back and neck to strip meat off bones. Its long arms were also used for wrestling and restraining prey, and the three-fingered hands were tipped with large claws to grip and tear flesh. It is believed to have hunted by ambush, as it was not built for long distance pursuits. Whether or not Allosaurus hunted in groups or cared for its young is still debated. Cannibalism has been recorded in Allosaurus, just as with Tyrannosaurus.
In spite of its fearsome weapons, Allosaurus was not immune to attack itself. Many specimens bear serious injuries from fights with prey or other predators including other Allosaurus, some of which never healed. The most famous specimen, nicknamed "Big Al", possessed broken ribs, broken tail vertebrae, a badly wounded arm, pelvis, shoulder, and worst of all, an infected broken toe that eventually killed the dinosaur because it could no longer hunt. One specimen bears a fatal wound inflicted by a Stegosaurus tail spike, while yet another bears wounds suggested to have been inflicted by a Diplodocus or Brontosaurus tail. One specimen even had a broken and re-healed jaw. Simply put, Allosaurus lived a dangerous life, one shared by many living and extinct predators the world over.
As a result of its fame and the high interest in understanding its life, Allosaurus has appeared many times in movies, television and documentaries. In older public media, it has often been confused with Tyrannosaurus, such as Ray Harryhausen's movie The Valley of Gwangi. One of the reasons for this is because in first years after Tyrannosaurus was discovered in the early 20th century, replicas of Allosaurus bones were used to complete the missing areas of the skeleton. More recent media and scientific discoveries have since corrected this.
Appearances[]
The Timekeeper[]
An Allosaurus attacked 9-Eye when she traveled to the Jurassic period.
Toy Story 3[]
Lotso is seen hugging a brown Allosaurus toy, which was among one of the many toys living in Sunnyside Daycare.
Mickey Mouse[]
A Goofy version of an Allosaurus makes a cameo in "Outta Time".
Penn Zero: Part-Time Hero[]
An Allosaurus served as Penn's steed in "The Old Old West" and "Amber".
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