Allosaurus: The Apex Predator of the Late Jurassic Period

Allosaurus was one of the largest theropods to have ever existed and inhabited Africa, Europe, and North America about 150 million years ago. The Allosaurus was a genus of the large Carnosaurian dinosaurs, which consists of other theropod dinosaurs.

Allosaurus Key facts

Key FactDetail
Allosaurus pronunciationa-luh-saw-ruhs
Meaning of NameDifferent lizard
Type SpeciesAllosaurus fragilis
When it Lived155.7 to 89.3 MYA
PeriodLate Jurassic
EpochLate/Upper Kimmeridgian to  Early/Lower Turonian
Length28 to 39 ft
Height15 ft at hips
Weight2.5 to 5.0 tons
MobilityMoved on two legs
First Discovery1869 by Ferdinand Vandiveer Hayden
Location of First FindColorado, USA
First Described1877 Othniel Charles Marsh
HolotypeYPM 1930

Allosaurus Origins: Taxonomy, Timeline, and Discovery

The name of this dinosaur is derived from the Greek words ‘allos’ meaning ‘different’, and ‘sauros’ meaning ‘lizard’. It was given this name because, at the time of discovery, the unique shape of the vertebrae were unlike other dinosaurs. This fascinating creature belongs to the Theropod group, a family of bipedal dinosaurs known for their predatory nature. Within this group, it is a part of the Allosauridae family, and its type species is Allosaurus fragilis. There are also several subspecies, including Allosaurus europaeus, Allosaurus jimmadseni, Allosaurus lucasi, Camptonotus amplus, and Labrosaurus sulcatus.

Allosaurus: The Fierce Predator of the Late Jurassic Era
image by Fred Wierum is license under CC BY-SA 4.0

The timeline of the Allosaurus is set in the Late Jurassic period, specifically from the Late Kimmeridgian to the Early/Lower Turonian epoch. This was a time when the Earth was a vastly different place, teeming with a variety of life forms that are now extinct.

The first discovery of Allosaurus remains dates back to 1869 in Colorado, USA. The credit for this significant find goes to American geologist Ferdinand Vandiveer Hayden. However, it wasn’t until 1877 that these fossils were officially described by another American paleontologist, Othniel Charles Marsh. This marked the beginning of our understanding of this fascinating creature.

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Fossil Evidence

The first fossils were discovered in the late 19th century. The initial discovery was made in 1869 by Ferdinand Hayden in the Morrison Formation in Colorado, USA. This formation, a sequence of sedimentary rock, is renowned for its rich dinosaur fossils from the Late Jurassic period. The first specimen, however, was not described until 1877 by paleontologist Othniel Charles Marsh.

image by Loves Art  is license under CC BY 2.5

Later finds have significantly expanded our understanding of this fascinating creature. Allosaurus fossils have been unearthed across a wide geographical range, including Portugal and Japan, indicating that this dinosaur had a broad distribution during the Jurassic period. The number of fossils found is substantial, with over sixty partial to nearly complete skeletons discovered to date. This abundance of fossils has made this one of the best-known dinosaurs.

The fossils found include a variety of types, from individual bones and teeth to nearly complete skeletons. The degree of preservation varies but some specimens are remarkably well-preserved, providing valuable insights into the dinosaur’s anatomy and life history. Notable specimens include “Big Al,” a nearly complete skeleton discovered in Wyoming, and the Cleveland-Lloyd Dinosaur Quarry in Utah, which has yielded a wealth of Allosaurus fossils.

Allosaurus Size and Description

This carnivorous dinosaur was a formidable creature in its time. Its physical characteristics speak volumes about its predatory lifestyle and the harsh environment it inhabited.

Short description of Allosaurus

It was a large theropod dinosaur characterized by a long, narrow skull equipped with dozens of sharp, serrated teeth. Its body was robust and supported by a strong vertebral column. The dinosaur’s forelimbs were relatively short but ended in three sharp claws that were ideal for grasping prey. Its hind limbs were powerful and built for speed, suggesting that this was a fast and agile predator. The long, muscular tail served as a counterbalance and a stabilizer during fast pursuits and sudden turns.

Size and Weight of Type Species

Estimates of size and weight vary, but it was undoubtedly one of the larger predators of its time. The dinosaur typically measured around 28 feet in length, though some specimens suggest individuals could reach up to 39 feet. Its height at the hips was approximately 15 feet. Weight estimates also vary, with some suggesting that it could weigh between 2.5 to 5 tons.

image by Steveoc 86 Marmelad Scott Hartman, [4], Henrique Paes [5]. is license under CC BY-SA 2.5

Allosaurus Games

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The Dinosaur in Detail

This creature embodied a unique blend of power, agility, and adaptability. Its distinctive features set it apart from other dinosaurs and reflect its survival instincts honed over millions of years.

The Allosaurus’ skull was not just a feeding tool but a sophisticated sensory platform. Its large, forward-facing eyes provided excellent binocular vision–a crucial advantage for a predator. The skull was also remarkably light due to numerous openings, reducing the weight without compromising strength.

The dinosaur’s forelimbs, though shorter than its hind limbs, were incredibly strong and ended in three sharp claws. These claws were likely used to grasp prey and may have been employed in predatory behavior like raking and slashing.

Notable specimens, such as “Big Al,” have contributed significantly to our understanding of Allosaurus. “Big Al,” in particular, has provided insights into the dinosaur’s growth patterns, health issues, and possible behavior. The specimen exhibits numerous injuries, suggesting a life filled with violent encounters and hardships.

The Allosaurus in its Natural Habitat and Environment

The Allosaurus was a creature of its environment, shaped by and in turn shaping the world around it. It lived during the Late Jurassic period, a time when the earth was a vastly different place than it is today. Found across a wide range, this predator would have stalked across a paleocontinent known as Laurasia–made up of modern North America and Asia. 

The Late Jurassic was characterized by warm, humid climates and vast coniferous forests, fern prairies, and lush river valleys. As a top predator, our dinosaur would have been a key player in these ecosystems, influencing the distribution and behavior of other animals. Its diet primarily consisted of large herbivorous dinosaurs, indicating that it likely frequented areas where these prey animals congregated, such as watering holes and feeding grounds.

This was a bipedal dinosaur, moving primarily on its two powerful hind limbs. This locomotion style, combined with its large size, suggests that Allosaurus was likely a pursuit predator, chasing down its prey over short distances. Its social behavior is still a matter of debate among scientists, with some suggesting that it may have been a solitary hunter while others propose that it may have hunted in packs.

The dinosaur’s senses, including its keen vision and possibly acute sense of smell, would have been crucial for finding prey and avoiding danger. Its large, sharp teeth and powerful jaws suggest that it was capable of delivering devastating bites, making it a formidable predator.

Interesting Points about Allosaurus

  • This is one of the best-known dinosaurs due to the abundance of its fossils. This has allowed scientists to gain a detailed understanding of its anatomy, growth, and possible behavior.
  • The dinosaur’s name, Allosaurus, means “different lizard,” reflecting its unique skeletal features that set it apart from other dinosaurs known at the time of its discovery.
  • It was a top predator in its ecosystem, preying on large herbivorous dinosaurs. Some fossils even show evidence of Allosaurus bites on other dinosaurs, providing direct evidence of its predatory behavior.
  • The dinosaur’s forelimbs, while shorter than its hind limbs, were incredibly strong and ended in three sharp claws. These claws may have been used in predatory behavior like raking and slashing.
  • Notable specimens, such as “Big Al,” have provided valuable insights into the life history of Allosaurus. “Big Al,” in particular, shows evidence of numerous injuries, suggesting a life filled with violent encounters and hardships.

Contemporary Dinosaurs

In the grand theater of the Jurassic period, the Allosaurus, a creature of formidable presence, shared its world with a diverse cast of Laurasian dinosaurs. Among these were the Stegosaurus, Apatosaurus, Diplodocus, and Camarasaurus. These herbivores would have needed adaptations in order to survive amongst our dangerous predator, the Allosaurus.

The Stegosaurus, with its iconic plates and spikes, was considerably smaller than the Allosaurus, yet it was far from defenseless. One can imagine the Allosaurus cautiously navigating around a Stegosaurus, respecting the reach of its thagomizer–the array of spikes on its tail. This interaction paints a picture of a world where size was not the only determinant of survival, but also the ability to defend oneself.

The Apatosaurus and Diplodocus, giants of the Jurassic period, presented a different kind of challenge. The Apatosaurus, with its massive size and strength, may have deterred the Allosaurus despite the predator’s formidable hunting skills. The Diplodocus hadits long, whip-like tail, which could have been a formidable defensive weapon keeping the Allosaurus at bay. These interactions hint at a complex dynamic where the Allosaurus had to weigh the risks and rewards of hunting such large prey.

The Camarasaurus, though not as large as the Diplodocus or Apatosaurus, had a robust build and likely traveled in herds to provide safety in numbers. This social behavior could have presented a challenge for the Allosaurus, forcing it to strategize and perhaps target younger or weaker members of the herd.

In this vibrant ecosystem, the Allosaurus, Stegosaurus, Apatosaurus, Diplodocus, and Camarasaurus coexisted. The Allosaurus, as the apex predator, was a central figure in this narrative. Its interactions with its contemporaries, whether as a hunter or competitor, shaped the dynamics of this prehistoric world. Through this lens, we gain a deeper understanding of this dinosaur and the world it inhabited.

Featured Image Credit: Fred WierumCC BY-SA 4.0, via Wikimedia Commons


“Please note that the information in this article is based on various sources, drawing on scientific research, fossil evidence, and expert analysis. We aim to provide a comprehensive and accurate overview of the dinosaurs, but please be aware that our understanding of dinosaurs and their world is constantly evolving as new discoveries are made.”

Article last fact checked: Joey Arboleda, 06-09-2023