Allosaurus facts for kids

Kids Encyclopedia Facts
Replica of Allosaurus skull (San Diego Natural History Museum).
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Allosauridae
Genus: Allosaurus
Marsh, 1877
The skeletal mount of Allosaurus, posed as scavenging an Apatosaurus.
Allosaurus in a Charles R. Knight life restoration.

Allosaurus was a large theropod dinosaur from the Jurassic period, a predatory carnivore. It was one of the largest predators of its time.

Allosaurus averaged 8.5 metres (28 ft) in length, though some remains suggest it could reach over 12 meters (39 ft). Its three-fingered forelimbs were smaller than its large hind legs, and the body was balanced by a long, heavy tail. It weighed up to 1.4 tons (3086 lbs).

It is the most common large predator found in the Morrison Formation of North America. This formation was laid down 155 to 145 million years ago, in the Jurassic.

Allosaurus was at the top of the food chain. It preyed on large herbivorous dinosaurs and perhaps even other predators (e.g. Ceratosaurus). Their prey included ornithopods, stegosaurs, and sauropods.

Allosaurus had cooperative behavior, and hunted in packs.

Groups have been found together in the fossil record. This might be evidence of pack behavior, or just the result of lone individuals feeding on the same carcass.

Remains of many individuals have been found, including some which are almost complete. Over sixty individuals from one species have been found.

What did it look like?

The Allosaurus was a large carnivorous dinosaur that walked on two legs and had two arms on the front of its body. Their skin was green or brown with fading red stripes on their back. This dinosaur could grow to be 12 meters long (39 feet) 5 meters tall (16.5 feet) and weigh up to about 1.4 tons (3086 lbs)! This dinosaur had a very long head, 90 cm (3 ft), with many 5 to 10 cm teeth. The Allosaurus did not look like the other dinosaurs that existed at that time. Because of this, the word Allosaurus means "different lizard".

The Allosaurus is in the theropod (meaning "beast foot") family. Allosaurus had two arms. Its arms were longer than those of the T.Rex with large wicked claws. Allosaurus was bipedal.

Allosaurus had 2 crests above its eyes which may have been used for mating display.

What did they eat?

DMSN dinosaurs
Allosaurus and Stegosaurus skeletons, Denver Museum of Nature and Science

Allosaurus were carnivorous dinosaurs and ate about 60 pounds a day. Allosaurus hunted in small groups which allowed them to take down even the largest prey. In the same way as raptors would, only slightly smaller groups. They even ate the gigantic Apatosaurus (which used to be called Brontosaurus) even though the Apatosaurus was more than three times the size of an Allosaurus. The Allosaurus was also likely to have hunted Stegosaurus, sauropods and ornithopods.

Young baby Allosaurus might have eaten insects like dragonflies and centipedes, and other small animals. When about two years old, Allosaurus might have eaten small dinosaurs (Othnielia, Dryosaurs and so on).

Allosaurs competed for food with ceratosaurs when they first arrived but may have eventually driven the ceratosaurs to extinction. Allosaurus's teeth were thin and serrated not made to puncture bone but to strip bits of meat off a carcase. Often Allosaurus left pieces of meat on the bone that other predators like Ornithelestes would scavenge.

The shape of the Allosaurus skull limited binocular vision to 20° of width, slightly less than that of modern crocodilians. As with crocodiles, this may have been enough to judge prey distance and time attacks. The similar width of their field of view suggests that allosaurs, like modern crocodiles, were ambush hunters.

Finally, the top speed of Allosaurus has been estimated at 30 to 55 kilometers per hour (19 to 34 miles per hour).

When did they live?

Like all dinosaurs, Allosaurus lived in the Mesozoic era. Mezo means middle so Allosaurus lived in the middle era. They lived in that era's late Jurassic period, between about 154 and 115 million years ago.

How were they discovered?

Allosaurus SDNHM

The first fossil of an Allosaurus to be discovered was found in the USA state of Colorado, in 1869. At first, the people who found it thought it was a petrified horse hoof instead of a dinosaur bone. In 1991 a complete Allosaurus skeleton was discovered. This Allosaurus was named "Big Al". When scientists looked at the skeleton they discovered that "Big Al" was actually an Allosaurus teenager. They also discovered that this young Allosaurus was about 8 meters (26 feet) long! "Big Al" was made famous by a TV programme called The Ballad of Big Al also called Walking with Dinosaurs: Allosaurus. This program showed what Big Al's life could have been like. They are also one of the most common dinosaurs in museums from the Jurassic time period.

Cleveland-Lloyd discoveries

The fossil site known as the Cleveland-Lloyd Dinosaur Quarry in Emery County, Utah was known in 1927, but major operations did not begin there until 1960. An effort from nearly 40 institutions got thousands of bones between 1960 and 1965. The quarry is notable for the many Allosaurus remains, the condition of the specimens, and our ignorance of its ancient origin. It is estimated that the remains of at least 46 A. fragilis have been found there, out of at least 73 dinosaurs. The fossils found there are disarticulated (separate) and well-mixed.

Suggestions as to how it arose include animals getting stuck in a bog, to becoming trapped in deep mud, to falling victim to drought-induced mortality around a waterhole, to getting trapped in a spring-fed pond or seep. Regardless of the cause, the great quantity of well-preserved Allosaurus remains means the animal is one of the best-known theropods. Individuals of almost all ages and sizes are found, from less than 1 meter (3.3 ft) to 12 meters (39 ft) long.

In popular culture

Allosaurus in Baltow 20060916 1500
Allosaurus model in Bałtów, Poland.

Allosaurus, like Tyrannosaurus, has come to represent the quintessential large, carnivorous dinosaur in popular culture.

Allosaurus is the official state dinosaur of Utah, in the United States.

It is a common dinosaur in museums. A number of museums cooperated in excavations at the Cleveland Lloyd Dinosaur Quarry. By 1976, museums in eight countries on three continents had Cleveland-Lloyd allosaur material or casts. Allosaurus is the official 'state fossil' of Utah.

Allosaurus is top predator in both Arthur Conan Doyle's 1912 novel, The Lost World, and its 1925 film adaptation, the first full-length motion picture to feature dinosaurs.

Allosaurus was used as the starring dinosaur of the 1956 film The Beast of Hollow Mountain, and the 1969 film The Valley of Gwangi. Gwangi is billed as an Allosaurus, though Ray Harryhausen based his model for the creature on Charles R. Knight's depiction of a Tyrannosaurus. Allosaurus appeared in the second episode of the 1999 BBC television series Walking with Dinosaurs and the follow-up special The Ballad of Big Al, which speculated on the life of the 'Big Al' specimen, as revealed by the numerous injuries and pathologies in its skeleton.

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Allosaurus Facts for Kids. Kiddle Encyclopedia.