Allosaurus: A Gigantic Predator Known for Flesh Grazing and Potential Cannibalism

Essential Facts

From approximately 157 to 145 million years ago, Allosaurus — a formidable predatory dinosaur — roamed the lands of North America and Europe.

Allosaurus Size

According to the fossil record, this creature was quite prevalent. And let’s not forget its immense size! A mature Allosaurus could reach lengths of 34 feet (10.4 meters), stand 9 feet (2.8 meters) tall at the hip, and weigh up to 3.2 tons (2.9 metric tons).

Even the mightiest predators face challenges. Enter "Big Al," a prime example of this.

Allosaurus Skeleton Discoveries

A young Allosaurus, famously nicknamed "Big Al," once roamed the region now known as north-central Wyoming. Researchers later recovered nearly 95 percent of this carnivorous dinosaur's skeleton.

Upon examining the remains (which could belong to either a male or female), scientists identified at least 19 distinct bone fractures. These injuries affected multiple vertebrae, toe bones, and ribs. Additionally, there were signs of a severe infection in the right foot.

If the discovery of the first "Big Al" intrigued you, the sequel will captivate you even more. Unearthed in a Wyoming quarry in 1991, "Big Al" was followed by the discovery of another Allosaurus skeleton in 1996, aptly named "Big Al 2."

Similar to its predecessor, this specimen showed extensive damage. Numerous bones had been fractured or injured, only to heal over time. However, a hip injury remained unhealed and may have contributed to the demise of "Big Al 2."

Other Allosaurus fossils also reveal evidence of significant injuries. To truly understand these findings, it’s essential to consider the dinosaur’s role and challenges within its ecosystem.

Allosaurus Habitat & Neighbors in the Jurassic

Allosaurus thrived during the Late Jurassic Period, a time when massive herbivorous dinosaurs known as "sauropods" roamed the Earth. Fossils of these sauropods are frequently discovered alongside Allosaurus remains.

At Dinosaur National Monument, located on the Utah-Colorado border, a preserved quarry allows visitors to observe a chaotic mix of fossils that have remained together for approximately 149 million years.

In addition to Allosaurus fossils, this site contains bones of long-necked sauropods like Diplodocus, Camarasaurus, and Apatosaurus. Remains of the spiky-tailed herbivore Stegosaurus are also found here.

These herbivorous dinosaurs were among the many that Allosaurus encountered. Competition for food was fierce, with rivals like the 39-foot (11.9-meter) Torvosaurus and the horned Ceratosaurus, which could exceed 19 feet (6 meters) in length. The latter made a brief appearance in "Jurassic Park III" (2001).

Allosaurus vs T-Rex Bite Force

Allosaurus possessed a relatively weak bite force compared to other dinosaurs. The bite strength of Tyrannosaurus rex, which lived millions of years after Allosaurus, was potentially four times greater.

Allosaurus Skull

Despite its limitations, Allosaurus excelled under stress; scientific models indicate its skull could endure significant physical stress.

In 2013, paleontologist Eric Snively and his team utilized computer simulations to explore how this dinosaur dismantled its prey. Their findings suggest Allosaurus might have acted similarly to a giant falcon during feeding.

The dinosaur's skull was lightweight, and its neck muscles were uniquely structured. Through simulations, Snively and his team demonstrated that Allosaurus could effortlessly strip flesh from carcasses by clamping onto meat with its jaws and pulling its head backward, a behavior mirrored by modern falcons.

Allosaurus Claws

Unlike falcons, which have wings for flight, Allosaurus possessed clawed forelimbs. Kenneth Carpenter, a dinosaur expert, noted in 2002 that these arms allowed Allosaurus to "seize moderately large prey and pull it closer to its body."

Allosaurus Diet

What constituted "moderately large prey" for a voracious Allosaurus? Likely candidates included beaked herbivores such as the 23-foot (7-meter) Camptosaurus or young sauropods.

If Allosaurus preyed on adult sauropods, scientists remain uncertain about its methods. Some Late Jurassic sauropods weighed 24 to 34 times more than the largest Allosaurus, making them formidable targets. Some researchers believe Allosaurus focused on juveniles, sick, or deceased sauropods, avoiding healthy adults altogether.

Alternatively, Allosaurus might have used its jagged teeth to tear flesh from living sauropods in non-lethal attacks. This speculative feeding strategy is referred to as "flesh grazing," a truly fascinating concept.

Bite marks indicate that Stegosaurus was occasionally prey. However, attacking such an armored dinosaur could be risky. One Allosaurus pubic bone bears a significant injury matching the size and shape of a Stegosaurus tail spike, suggesting the predator may have been stabbed in the groin.

Proof of Allosaurus Cannibalism

Another unsettling discovery: Allosaurus is believed to have engaged in cannibalism.

Stephanie Drumheller, a geoscientist at the University of Tennessee, spearheaded a study published in the May 2020 issue of Plos One. The research examined 2,368 fossil bones from a Jurassic quarry in Colorado, revealing that nearly 29 percent displayed bite marks from serrated-toothed carnivorous dinosaurs.

While many of the bite-marked bones belonged to sauropods and other herbivores, some were identified as Allosaurus remains.

Given that Allosaurus is the most frequently found predator at this excavation site, it’s highly plausible that these findings point to cannibalistic tendencies.

Allosaurus Fossils Among Graveyard of Killer Dinosaurs

Any discussion about Allosaurus must include Utah’s enigmatic Cleveland-Lloyd Dinosaur Quarry (CLDQ).

Fossils from 10 different dinosaur species have been unearthed here, including herbivores like Stegosaurus and Apatosaurus. However, an astonishing 66 percent of the bones discovered at the CLDQ belonged to Allosaurus.

In total, the quarry has produced remains from at least 46 Allosaurus skeletons, ranging from juveniles to fully grown adults. All perished in the same location.

The mystery lies in why this is the case. Why is Allosaurus so disproportionately represented at the CLDQ? Over the years, several theories have been proposed to explain this phenomenon.

One possibility is that the CLDQ functioned as a Jurassic predator trap.

This scenario suggests that herbivores became trapped in deep mud or a similar substance, drawing in carnivores that also met their demise. The accumulation of bodies would then lure even more predators, resulting in a disproportionate number of predator remains compared to prey.

However, skeptics argue that the lack of bite marks on the bones found at the quarry undermines this theory.

Another theory suggests the CLDQ might have been the site of a toxic watering hole — or a regular one that eventually dried up, causing dehydrated dinosaurs to perish along its edges. An alternative explanation attributes the mass accumulation of skeletons to flooding.