How giant dinosaurs turned their skulls into weapons

Tyrannosaurus rex had a skull like a sledgehammer. The skulls of spinosaurs and allosaurs, by contrast, worked like blades. A new study shows that giant meat-eating dinosaurs didn’t all crush bones with their skulls like T. rex. Some dinosaurs sliced flesh instead.

Researchers examined bite strength in 18 species of theropod dinosaurs. They found that while T. rex had a skull suited for short, powerful bites, others relied on different strategies.

Despite their massive size, spinosaurs and allosaurs had much weaker bites. They didn’t need to crush prey. They slashed and ripped instead.

“Tyrannosaurs evolved skulls built for strength and crushing bites,” said Andrew Rowe of the University of Bristol. “Other lineages had comparatively weaker but more specialized skulls.”

These findings challenge the idea that all giant predators hunted the same way. Instead, large carnivorous dinosaurs followed separate evolutionary routes.

Two ways to hunt

The researchers used advanced 3D models to test skull biomechanics. Their work reveals two main strategies among giant predators. Tyrannosaurs had strong skulls with high stress tolerance. Others evolved to reduce skull stress instead of increasing power.

The skull of T. rex allowed powerful muscles to deliver bone-crushing bites, even at the cost of stress. By contrast, megalosauroids and allosauroids developed slender skulls that dispersed pressure more evenly. They focused on slicing flesh rather than smashing bone.

These two feeding strategies reflect deep ecological divergence. Tyrannosaurs likely hunted large, armored prey. They needed brute strength. Spinosaurs and allosaurs, on the other hand, went for mobility and flexibility.

Dinosaur skulls and bite strength

The study also tested how skull stress changed with dinosaurs body size. Surprisingly, bigger skulls didn’t always mean more stress. In fact, smaller theropods often experienced more cranial strain. That happened because their skull shapes weren’t built to manage strong bite forces.

The researchers scaled all skulls to the same size to isolate shape effects. Herrerasaurus and Ceratosaurus, both small, showed the highest stress. In contrast, giants like Spinosaurus and Acrocanthosaurus had low stress levels.

T. rex stood out. Despite high stress levels, its skull could manage the pressure. Its anatomy – fused bones, deep jaws, expanded skull rear – helped stabilize the force. This let it crush bones efficiently.

How dinosaurs used their skulls

“I tend to compare Allosaurus to a modern Komodo dragon in terms of feeding style,” Rowe said. “Large tyrannosaur skulls were instead optimized like modern crocodiles with high bite forces that crushed prey.”

Unlike their bone-crushing cousins, allosaurs had wider gapes and more flexible skulls. They likely used a slash-and-tear technique. Spinosaurs, possibly semi-aquatic, had long snouts and narrow skulls. These helped them twist and shake prey, possibly even catching fish.

Even among tyrannosaurs, not all had the same build. Some, like Alioramus, kept slender skulls into adulthood. They may have gone after smaller, faster prey, avoiding direct conflict with bulkier relatives.

Jaw mechanics of large dinosaurs

The researchers also studied jaw mechanics. T. rex and its relatives had jaws that got more stressed with size. But other dinosaurs didn’t follow that trend. Allosaur jaws, for instance, showed a clear pattern of reduced stress as they grew.

The mandible played a key role in feeding. In tyrannosaurs, stress built up in the back of the jaw. In others, like Allosaurus, pressure concentrated near the front. This difference hints at how they bit, held, and processed food.

Interestingly, the study found that mandibles generally experienced more stress than skulls. That makes sense, since jaws deal directly with the prey during feeding.

Skull shape mattered more than size

The research also explored the role of skull shape. Even when scaled to equal size, differences remained. Shape – not just size – affected how much stress the skulls endured. Spinosaurus and Acrocanthosaurus performed well, showing strong but low-stress skulls.

Some medium-sized predators, like Neovenator, had surprisingly high stress levels. Others, like Giganotosaurus, managed stress better, suggesting a more balanced design.

Skull ornamentation didn’t seem to affect stress much. Features like crests or horns, seen in dinosaurs like Dilophosaurus, had little impact on bite mechanics.

Evolution shaped more than looks

These findings show that dinosaur feeding performance was shaped by more than size or skull strength. Tyrannosaurs evolved skulls built for force and domination. Other dinosaurs survived through flexible skulls and specialized feeding. The coexistence of different dinosaurs likely reduced direct competition.

This biomechanical diversity suggests dinosaur ecosystems supported many hunting strategies.

“Carnivorous dinosaurs took very different paths as they evolved into giants in terms of feeding biomechanics and possible behaviors,” said Rowe.

In the end, evolution didn’t choose one right way to hunt. It allowed many. Some dinosaurs crushed bones, and others sliced meat. Their success as apex predators came through diverse biomechanical adaptations.

The study is published in the journal Current Biology.

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