Allosaurus

Allosauridae

Living between 156 and 145 million years ago, Allosaurus were the largest carnivores of the Jurassic and lived at a time that allowed them to spread across the world. Almost every continent has had a dinosaur identified as an Allosaurus at some time (many of these though are no longer valid, yet are still considered to be closely related to the Allosaurus).

Like many of the more famous dinosaurs, the Allosaurus also became its own family name, meaning an Allosaurus is an allosaurid from the allosauridae family (simply put, a Crocodile is a crocodilian, but not all crocodilians are Crocodiles !), and as the number of new discoveries has grown over the years, so has the family of allosaurids. Like many species, several dinosaur remains have been described as Allosaurus . However several of these have recently been removed and placed in the allosaurid family (meaning they are still closely related to Allosaurus but they are not actually an Allosaurus ) or have found themselves in another family all together. The following is a list of the names Allosaurus has either been called or have been misidentified as:

Allosaurus Atrox (was actually a Creosaur) A. Ferox , A.Medius (was a Dryptosaur), A. Meriani (a Ceratosaur), and A. Sibiricus (possibly a Therizinosaur). A. lucaris A. Sibiricus, ANTRODEMUS Valens, CAMPTONOTUS amplus, CAMPTOSAURUS amplus, CHILANTAISAURUS, C. maortuensis, C. Sibiricus, C. tashuikouensis,   CREOSAURUS atrox, EPANTERIAS amplexus, HYPSIRHOPHUS), KATSUYAMASAURUS  LABROSAURUS, L. ferox  LAELAPS trihedrodon, LOURINHANOSAURUS, L. antunesi,  MADSENIUS", MEGALOSAURUS oweni  NEOVENATOR,  N. salerii,   PIATNITZKYSAURUS,  P. floresi, POEKILOPLEURON valens, SAUROPHAGANAX maximus, SAUROPHAGUS, SZECHUANOSAURUS,  S. campi,  S. yandonensis, S. zigongensis, VALDORAPTOR, V. oweni, WAKINOSAURUS, W. satoi and WYOMINGRAPTOR . " 

In fact there are only three valid species of Allosaurus at this time: Allosaurus fragilis, A. maximus and A. jimmadseni.

Thanks to large finds in North America , a lot is known about Allosaurus (44 individuals were dug out of a pit that resembles the bone beds at the bottom of the Le Brae tar pits). These finds have given us a window into the world of the Allosaurus.

They lived hard and active lives, and none more so then the Allosaurus dubbed Big Al. Al's skeleton shows a body that lived a hard, stressful life! The skeleton shows no more then 19 deformities on its body that were caused by disease and injury (the museum has a display full of bones that show evidence of injury and disease), with the majority showing signs of healing. These injuries show that Allosaurus lived a life that would never have allowed many of them to achieve old age (Al himself was a sub-adult when he died).

Another find in Wyoming shows an allosaur-nesting site filled with adult and young allosaur remains. The site also contains many herbivorous dinosaur bones that show teeth marks from both adult and young Allosaurus. Conspicuous is the absence of juvenile allosaur remains in this area. This seems to point at the young being kept in or near the nest until a certain age when they were possibly driven off so that the family could protect and care for a new batch of chicks (possibly protecting the chicks from jealous attacks from the juveniles themselves). These juveniles could form bands or packs that would roam the land, hunting and scavenging and generally avoiding large adult groups until they grew to full maturity.

The Allosaurus itself was a strange animal. Often called a Morphodite, it seemed to be an animal whose features did not suit any of the roles it took. When compared to other carnivores, an Allosaurus had small teeth, a weak lower jaw and would not have possessed binocular vision (important for depth perception). The lower jaw of the Allosaur might have been weaker because of the effective tool the top jaw had evolved into. The major pray of the Jurassic where the large sauropod dinosaurs like Brachiosaurus, and it has long been disputed that a three tonne Allosaur would have difficulty killing a 50 to 80 tonne giant like a sauropod. But if the allosaur hunted in packs like lions, they could amplify their strength by increasing their numbers. One allosaur would be no match for a Brachiosaur; but ten Allosaurus , working in a team, could make an extremely effective weapon.

Walking with dinosaurs. tm and many other palaeontologists have claimed that there was an Allosaur living in Australia during the cretaceous albeit a smaller version that has been dubbed a Polar allosaur. But what really are the chances of this? Likely none. For starters all of this is based on a single anklebone that could have belonged to any number of carnosaurs. Australia was also a long way from North America where most true allosaur remains are found, but there is a neighbour that might fit the bill. Australia , and Victoria in particular where the anklebone was found was connected to Antarctica throughout the Mesozoic. And a recent find in Antarctica might be our ‘ Allosaurus' . Crylophosaurus was a large Jurassic carnivore that roamed Antarctica, and was in easy striking distance of Australia . Though a Jurassic dinosaur, its is more likely that this crest-headed carnivore survived around Victoria well into the cretaceous then a dinosaur that never even lived in the area!

 

All images and articles copyright © National Dinosaur Museum.


© 2005-9 National Dinosaur Museum
Website best viewed in Mozilla Firefox or Microsoft Internet Explorer