One of The Fiercest Hunters of the Late Jurassic Period

Species Introduction

Allosaurus, or as its name translates in Greek, "Different Lizard", is a decently large reptilian theropod belonging to the Allosauridae genus. This fierce carnivore walked the earth in the late Jurassic period around 154 and 144 million years ago when the evolution of dinosaurian life was at its peak. One of the most-famous and easily-identifiable dinosaurs in our society, it was equally a common predator in its time.
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Physical Appearance

Allosaurus was a powerful flesh-eating reptile that sported a bulky body and heavy bones. According to most paleontologists, it measured an approximate 12m in length and its height ranging from 8 to 12 meters. Its average weight was calculated to be an astonishing total of 1.5 tons, depending on the specimen. A biped, it walked on two legs and could reach impressive speeds of 30-55km per hour that remained unaffected by its considerably light build.

The fierce reptile also sported irregular vertebrae (hence the name "different lizard") and an S-shaped neck. Such anatomy gave it the advantage of a powerful attack.

Despite of its monstrous, clawed back legs, Allosaurus had short, three fingered forearms with sharp claws, usually the length of some 15cm.

The reptile's skull measured 90cm with small, bony knobs over reach eye that formed ridges on top of its head.

A Formidable Hunter

This savage killing machine reigned supreme over medium-sized sauropods like Diplodocus, Camarasaurus and the occasional Stegosaurus and large sauropods like Apatosaurus (usually sick or injured specimens) for a good reason.

Each of its monstrous jaws were equipped with sharp, serrated teeth measuring 5cm, used to tear apart the flesh of their prey, allowing it to savagely rip apart such petty herbivores who, despite their keen senses and efficient perception, couldn't stand a chance against its predatory capabilities.

However, despite some controversy, recent paleontological studies show that Allosaurus' bite was surprisingly weak and has shown to be less powerful than that of a lion's, despite the significant size difference.

If it wasn't a powerful bite, what did make Allosaurus such an elite hunter?

Researchers have instead discovered a far more effective method this apex predator used to send its prey to their doom. Advantaged by its intellect, the reptilian monster approached its victims with the element of surprise.

The witty Allosaurus, sometimes hunting in groups of 2 or 3, would frequently stalk its prey from afar and execute a stealthy sneak attack. This is as its skull possessed the ability to withstand a force 15 times greater than its bite and therefore allowed the treacherous beast to forcefully drive its top jaw into its pitiful prey like an axe.

Such a well-planned method of offence resulted in shock and fatal blood loss, guaranteeing a brutal takedown and a chance to feed off of even the toughest Stegosaurus.

In fact, in a paper published in 2005 titled 'The Carnivorous Dinosaur' described evidence of an epic battle between the two species as palaeontologists have uncovered an Allosaurus tail vertebra bearing puncture in the shape of a stegosaurus tail spike.

Additionally, an Allosaur pelvic-bone was found with a deadly stab wound, likely received from its powerful-tailed opponent was also unearthed.

Brutal, stealthy and intelligent (a trait common among theropods), it is no wonder this savage reptile is nicknamed "The Lion of the Jurassic".

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Living Conditions: The Late Jurassic Period

140 millions of years ago, dinosaurs dominated the earth and the supercontinent Pangea split into two major continents: Laurasia and Gondwana. The motion of tectonic plates caused the eruption of many underwater volcanoes and led to rising water levels.

The frequency and variation in reptilian life has hit its highest point when Allosaurus roamed the earth. From large plant-eaters that fed on lush ferns and vegetation such as the palm-like cycads and bennettitaleans, to vertebrates like pterosaurs taking the skies with the appearance of some of the first birds, this prehistoric era was full of variety.

The shift of tectonic plates and the creation of wide expanses of shallow 'oceans' equally promoted a warm and humid environment where both terrestrial and marine life thrived in large coral reefs and dense forests.

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The Evidence?

One of the earliest fossils discovered by human beings, the first Allosaur remains were discovered in Colorado in 1877 and named by Othniel Charles Marsh who claimed that the unearthed fragments belonged to other distinctly similar species that, over time, turned out to be those of the newly-discovered Allosaurus. Marsh also coined the term

'Different Lizard' when picking a name for the prehistoric creature.

Another fossil find dated back to 1879 when a far more complete skeleton was uncovered at the Jurassic locality of Como Bluff, Wyoming (North America) by F.F. Hubbell.

Upon examination in 1903, Hubbell's discovery turned out to be one of the best-preserved theropod remains ever found.

Nonetheless, the most significant specimen was uncovered in 1991 with the combined efforts of the researchers from the Museum of the Rockies and those of the University of Wyoming Geological Museum. An almost perfectly intact skeleton was found in the state of Wyoming, near Shell, and was nicknamed "Big Al" by the team. This was followed by another advantageous find in 1996 by the same team and was dubbed "Big Al two".

Allosaurus were common and ever so diverse so many remains have long been stated to belong to other species, leading to many palaeontologists having to re-evaluate their original fossils and conclude that they all belonged to variations of the same species.

Several include: Antrodemus,‭ ‬Creosaurus and Labrosaurus, who are all grouped under the term 'Allosaurus'.

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According to fossil evidence, Allosaurus mostly inhabited prehistoric USA and ranked as one of the primary predators of the Jurassic in various regions of central North-America where Allosaurus population was high. Less frequent discoveries of fragmentary material also occurred further abroad but cannot be considered entirely valid due to a lack of evidence.

Nevertheless, remains of a dinosaur quite reminiscent to the Allosaur were discovered in Portugal and are referred to as A.‭ ‬europaeus and another group of palaeontologists in the North-east of Thailand have come across fossilised bones that may not identify as entirely valid.

Sources Used:

"DK Find Out! | Prehistoric Life: Allosaurus." DK Find Out! 2016 Dorling Kindersley Limited, 2016. Web. 10 Mar. 2016.

"BBC Nature: Prehistoric Life- Allosaurus."Http:// BBC UK, Oct. 2014. Web. 16 Mar. 2015. <>.

"Allosaurus." Dinosaurs and Barbarians. Word Press, 12 Nov. 2013. Web. 10 Mar. 2016. <>.

Castro, By Joseph. "Allosaurus: Facts About the 'Different Lizard'"LiveScience. TechMedia Network, 15 Mar. 2016. Web. 10 Mar. 2016.


Dave Smith. "Theropod Dinosaurs." Theropod Dinosaurs., n.d. Web. 20 Mar. 2016. <>

Waggoner, Ben. "The Jurassic Period." University of California- Museum of Paleontology, 2012. Web. 19 Mar. 2016.

"Allosaurus." N.p., 2010. Web. 16 Mar. 2016. <>.