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Allosaurus is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period. The name “Allosaurus” means “different lizard”. It is derived from the Greek allos and sauros. The first fossil remains that could definitively be ascribed to this genus were described in 1877 by paleontologist Othniel Charles Marsh. These remains became known as Antrodemus. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles. Indeed, it has been a top feature in several films and documentaries about prehistoric life.

Lived: 163.5 million years ago – 89.3 million years ago (Late Jurassic – Turonian)

Speed: 30 – 55 km/h

Scientific name: Allosaurus (Different lizard)

Scientific classification

  • Kingdom: Animalia
  • Phylum: Chordata
  • Clade: Dinosauria
  • Order: Saurischia
  • Suborder: Theropoda
  • Family: Allosauridae
  • Subfamily: Allosaurinae
  • Genus: Allosaurus


Allosaurus was a carnivore. It lived in the Jurassic period and inhabited Africa, Europe and North America. Its fossils have been found in places such as Utah, Colorado and Texas.


The name Allosaurus is derived from the Greek allos (“different” or “other”) and sauros (“lizard”). It was so-named because its vertebrae were different from any other dinosaur known at the time of its discovery in 1877.

Specifically, some of the vertebrae of Allosaurus fragilis (Latin for “fragile”) were concave on both sides and contained shallow cavities, giving them an hourglass shape — these features reduced the bones’ strength, while making them lighter. The hollow spaces in these neck and anterior back vertebrae are also found in modern birds and believed to have contained air sacs for respiration.


Allosaurus was an allosaurid, a member of a family of large theropods within the larger group Carnosauria. The family name Allosauridae was created for this genus in 1878 by Othniel Charles Marsh, but the term was largely unused until the 1970s in favor of Megalosauridae, another family of large theropods that eventually became a wastebasket taxon.

This, along with the use of Antrodemus for Allosaurus during the same period, is a point that needs to be remembered when searching for information on Allosaurus in publications that predate James Madsen’s 1976 monograph.


The dinosaur was a large bipedal predator. Its skull was large and equipped with dozens of sharp, serrated teeth. It averaged 8.5 m (28 ft) in length, though fragmentary remains suggest it could have reached over 12 m (39 ft).

Habits and habitat

The dino was a bipedal dinosaur, mirroring other advanced theropods. It was obviously ground-dwelling and carnivorous. It is speculated that the Allosaurus hunted ornithischian dinosaurs such as the Stegosaurus.


  • The Dinosaur lived around 150 million years ago in the late Jurassic Period.
  • The name Allosaurus means ‘different lizard’.
  • dinosaur was first described by Othniel Marsh in 1877 and become one of the first well known dinosaurs. Marsh also named and gave the first description of the Apatosaurus (Brontosaurus) in that same year.
  • Most dinosaur fossils have been found in the Morrison Formation, a distinctive band of sedimentary rock found in the western United States.
  • Skull and walked on two legs.
  • Its body and head were balanced by a long and heavy tail.
  • Like the Tyrannosaurs rex, the Allosaurus had short arms. It had three fingers that were each tipped with sharp, curved claws.

Life history

Skeletons at different growth stages on display, Natural History Museum of Utah

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 150 kilograms (330 lb) 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.

Allosaurus images

Also more: Alamosaurus dinosaurs

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