About Allosaurus
| Scientific Name (Genus) | Allosaurus |
| Meaning of Name | Different lizard allos (different) [Greek] - sauros (lizard) [Greek] |
| Classification | Saurischia, Theropoda, Allosauridae |
| Total Length | Approx. 9-12m |
| Diet | Carnivorous |
| Period | Late Jurassic (approx. 155-145 million years ago) |
| Species Name | Allosaurus fragilis Allosaurus europaeus Allosaurus jimmadseni Allosaurus tendagurensis |
| Year of Paper Publication | 1877 |
| Genus Name Publication | Marsh, Othniel Charles (1877). Notice of new dinosaurian reptiles from the Jurassic formation. American Journal of Science and Arts, 14, 514-516. |
Apex Predator of the Jurassic
Allosaurus was one of the largest carnivorous dinosaurs of its time, living in North America and Europe during the Late Jurassic. It is estimated to have weighed around 2 tons and was the apex predator of its terrestrial ecosystem. A characteristic feature is the pair of bony crests above its eyes, which varied in shape and size among individuals.
The Morrison Formation in the United States, where many Allosaurus fossils have been found, is thought to have been a savanna-like environment with distinct wet and dry seasons. In this environment, Allosaurus preyed on dinosaurs like Stegosaurus and young sauropods such as Diplodocus.
Thanks to the abundance of fossils, the growth process of Allosaurus is well understood. It had a lifespan of 22 to 28 years, experienced a growth spurt around age 15, and is thought to have been capable of reproduction by age 10.
The Allosauridae family also includes even larger relatives like Saurophaganax, indicating the richness of the Jurassic ecosystem.
The Hatchet Bite
Analysis of the Allosaurus skull has revealed that its bite force was not as strong as that of the later Tyrannosaurus. Therefore, it is thought to have hunted in a unique way, rather than crushing bones like Tyrannosaurus.
This hunting method is called the "hatchet bite." It involved using its strong skull and powerful neck muscles to bring its open upper jaw down on prey like an axe, inflicting deep gashes. It is presumed that this attack was not meant to kill the prey instantly but to cause massive blood loss, weakening it before the final kill.
Analysis of the Allosaurus skull shows that the overlap of its visual fields was about 20 degrees. While this overlap helps in judging distances to prey stereoscopically, it was not as developed as in Tyrannosaurus. However, its depth perception was likely comparable to that of modern crocodiles, which would have been sufficient for hunting.
Due to its lighter weight, it is estimated to have been able to run at top speeds of 30 to 50 km/h, which was a significant advantage in hunting. Its short forelimbs had three sharp claws, which are thought to have been useful for holding down and tearing apart prey.
Allosaurus's Social Behavior and Cannibalism
For a long time, it was thought that Allosaurus hunted cooperatively. However, recent studies suggest that, like modern crocodiles, they may have engaged in fierce competition with each other over prey. Supporting this, Allosaurus fossils have been found with bite marks from the same species and fractures in the abdominal bones, indicating intense conflict.
In 2020, direct evidence of cannibalism among Allosaurus was found in fossils from the Morrison Formation. It seems that to survive in harsh conditions, such as the dry season when prey was scarce, they would even eat their own kind.
"Big Al": Evidence of a Harsh Life
Source: Laws, R. R. (1996). Paleopathological analysis of a sub-adult Allosaurus fragilis (MOR 693) ... Montana State University-Bozeman.
The famous fossil specimen "Big Al" is essential for telling the story of the harsh life of Allosaurus. Discovered in Wyoming, USA, in 1991, this individual was a remarkably well-preserved specimen with 95% of its skeleton intact.
Subsequent research revealed that Big Al had suffered numerous injuries, including fractures and infections. An infection in its right foot, in particular, was severe and is presumed to have made walking difficult.
Furthermore, in 1996, an even better-preserved specimen, "Big Al 2," was discovered. This specimen showed evidence of 19 injuries, including a broken jaw and ribs, and an infection in its tail. These specimens eloquently testify to how full of struggle the life of the Jurassic king was.