terópodos
Late Jurassic, 150 million years ago
Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah, Wyoming; also Europe (Portugal) and Africa.
2.000Kg
5m
11m
Allosaurus was the great predator of the Jurassic, seventy million years before Tyrannosaurus rex appeared.
It also had a feature that is rarely mentioned: its bite was weaker than a modern lion’s. Its advantage was not jaw strength, but a completely different hunting technique that took palaeontologists a century to understand.
Allosaurus means “different lizard”. The name refers not to its appearance, but to its vertebrae. When Othniel Charles Marsh described it in 1877, he noticed that they were lightened and hollow, unlike those of any other reptile known at the time. This also explains the species name fragilis.
Those spaces were not a weakness. They made the skeleton lighter in an animal that needed to move quickly, the same principle seen in birds today.
Marsh named it during the Bone Wars, his fierce rivalry with Edward Drinker Cope to describe the greatest number of species. The race was a methodological disaster, with duplicate names and fossils dynamited to keep them from a rival, but it also brought many familiar dinosaurs to light.
An adult Allosaurus measured 8.5 to 9.7 metres long and weighed 1.7 to 2.3 tonnes. Palaeontologists use its height at the hips, around 3 metres, because it walked with its body horizontal and its tail extended behind it as a counterweight.
Exceptional individuals reached 11 or 12 metres. They were so large that they were once thought to belong to another genus, but these were isolated cases rather than the norm.
Compared with Tyrannosaurus rex, which reached 12–13 metres and nine tonnes, Allosaurus was smaller and far lighter. That lighter build is central to understanding how it hunted.
This is the surprising part.
In 2001, a team led by Emily Rayfield subjected an Allosaurus skull to finite element analysis, the same technique used to test bridges. The results revealed an unusual combination.
Its bite force was around 3,500 newtons, less than a modern lion’s and a fraction of the 35,000 estimated for T. rex. Yet its skull could withstand loads of up to 55,000 newtons without breaking. It was built to handle fifteen times more force than its own jaw muscles could produce.
The most likely explanation is that Allosaurus did not kill by clamping down, but by striking. It could open its mouth to roughly 80 degrees, then drive the upper jaw down into its prey using its neck muscles and the weight of its head. Sharp, serrated teeth acted like the edge of an axe and opened long, deep wounds.
Against an enormous animal it could not bring down immediately, the strategy made sense. A single killing bite was unnecessary if it could wound the prey and wait.
Its hands also helped: three fingers with curved claws up to 25 centimetres long, probably used to grip the prey’s flank.
Allosaurus shared its ecosystem with Stegosaurus, and fossil evidence shows that they fought.
An Allosaurus tail vertebra has a hole whose shape matches a Stegosaurus tail spike. The wound became infected, and the bone’s reaction shows that the animal survived for some time afterwards.
There are also Stegosaurus back plates with a U-shaped bite matching the snout of Allosaurus.
Two animals, two scars, one encounter. It is one of the few cases in palaeontology where a specific confrontation between two species can be reconstructed. It also explains why Stegosaurus carried that tail: it worked.
Allosaurus hunted or scavenged sauropods as well. Diplodocus bones have been found with its tooth marks.
It was agile for its size. Estimates vary between studies, but usually fall around 30–35 km/h. These figures come from models rather than direct measurement. Even so, it was much quicker than the nine-tonne T. rex, which probably could not run.
Allosaurus had binocular vision. Forward-facing eyes gave it depth perception and helped it judge attack distances.
It also had two bony crests above its eyes. They were too fragile for fighting and probably served for display or recognition. They may also have acted as a shade against the sun.
Allosaurus is the best-known Jurassic theropod, largely because of two discoveries.
The first is the Cleveland-Lloyd Dinosaur Quarry in Utah, which has produced remains from more than 46 Allosaurus individuals. This is puzzling: a normal ecosystem has many more prey animals than predators. The leading explanation is a natural trap, perhaps a mud pit where a herbivore became stuck, attracting carnivores that were then trapped in turn over many years.
The second is Big Al, discovered near Shell, Wyoming, in 1991. The skeleton is 95% complete, but it became famous for its medical record: nineteen injured bones, including broken ribs, infections and a badly damaged toe bone. It was a subadult that never finished growing and probably died from one of those infections.
Five years later, the same team found Big Al Two nearby, an even better-preserved specimen. Together they have given us one of the clearest individual life stories known for any carnivorous dinosaur.
Not every fossil comes from North America. Remains found around Lourinhã in Portugal have been described as a separate species, Allosaurus europaeus.
Geology explains why. During the Late Jurassic, the North Atlantic was only beginning to open, and the Iberian Peninsula was still connected to North America. The animals on both sides were very similar.
So Allosaurus did live on the Iberian Peninsula, only a few hours from here. Read the full story in which dinosaurs lived in Spain.
It is the comparison everyone makes, but one fact needs to be clear.
They never lived together. Allosaurus lived 155 to 145 million years ago; T. rex lived 68 to 66 million years ago. Around 80 million years separated them, more time than separates T. rex from us.
On paper, T. rex wins easily: it was four times heavier and had a bite ten times stronger. Allosaurus compensated with agility, better arms and a cutting technique instead of crushing. They were two different answers to the same problem, separated by an era.
For more comparisons, see the 10 most dangerous dinosaurs and the strongest dinosaur in history.
There is a life-sized Allosaurus in the park. It stands in the southern area, through the entrance on the right, and is one of the first dinosaurs you encounter.
Look at it with its hunting method in mind. It is not the largest model on the trail, but it shows that Jurassic predators had another way to hunt. A few metres away are Stegosaurus, whose tail left scars on Allosaurus, and Diplodocus, whose bones preserve its tooth marks. A Jurassic confrontation at full scale within twenty metres of trail.
The outdoor route runs among pine trees in Porto Cristo, Mallorca, with more than 100 life-sized dinosaurs from around 40 species. Profiles of them all are available in the dinosaur section.
🎟️Come and see Allosaurus up close. Tickets are available at tickets.dinosaurland.es, with €1 off each ticket bought online. See tickets, prices and booking information for rates and conditions, and dates and opening times for opening days.
Have a young dinosaur fan at home? Download our printable PDF of Allosaurus to colour in.
What does Allosaurus mean?
“Different lizard.” Othniel Charles Marsh chose the name in 1877 because its vertebrae were lightened and hollow, unlike those of other reptiles known at the time.
How big was Allosaurus?
It measured 8.5 to 9.7 metres long and stood about 3 metres tall at the hips, weighing 1.7 to 2.3 tonnes. Exceptional specimens reached 11 or 12 metres.
How fast could Allosaurus run?
Estimates place it at roughly 30–35 km/h, although results vary between models. It was clearly more agile than T. rex, which was probably too heavy to run.
Which had the stronger bite, Allosaurus or T. rex?
What did Allosaurus eat?
Other dinosaurs and carrion. Documented prey includes stegosaurs and sauropods, whose bones preserve its tooth marks.
Who won, Allosaurus or Stegosaurus?
Fossils show that both injured the other. An Allosaurus vertebra was pierced by a Stegosaurus spike, while Stegosaurus plates bear Allosaurus bite marks.
Did Allosaurus and T. rex live together?
No. Around 80 million years separated them: Allosaurus lived in the Late Jurassic and T. rex at the end of the Cretaceous.
Did Allosaurus live on the Iberian Peninsula?
Yes. Fossils from Lourinhã in Portugal have been described as Allosaurus europaeus. Iberia and North America were still connected in the Late Jurassic and shared similar wildlife.
Can you see a life-sized Allosaurus in Mallorca?
Yes. It is at Dinosaurland in Porto Cristo, in the southern area just through the entrance on the right, on a trail with more than 100 dinosaurs.
For decades, Allosaurus was described as a smaller T. rex, an early draft of the final design. It turned out to be the opposite: an animal that solved the same problem in another way, with less force and more technique.
Seventy million years before the king, the Jurassic already had its own. And it carried an axe instead of a nutcracker.
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