Not all giant predatory dinosaurs used their jaws for strong, bone-crushing bites according to a new study. Don’t get me wrong, you still wouldn’t want to be bitten by any of these ancient killers.
Tyrannosaurus rex attacking two Struthiomimus. Credit: Mohamad Haghani / Stocktrek Images / Getty Images Plus.
Tyrannosaurus rex was a 12m-long, 8-tonne carnivore. It is the archetypal massive meat-eating dinosaur and is rightfully known as the “King of the Dinosaurs”. Its 1.8m skull could easily have swallowed a human whole (thank goodness for the 66 million years of evolution separating our species from them). Their massive jaws were the business end of the world’s most powerful ever bite.
T. rex had a bite force of up to 60,000 Newtons. For comparison, lions have a bite force of about 1,300–2,000 N.
Many other large predatory dinosaurs lived during the “Age of Dinosaurs”. New research published in Cell Biology shows that they used their jaws in very different ways.
“Carnivorous dinosaurs took very different paths as they evolved into giants in terms of feeding biomechanics and possible behaviours,” says senior author Andrew Rowe of the University of Bristol, UK.
“Tyrannosaurs evolved skulls built for strength and crushing bites, while other lineages had comparatively weaker but more specialised skulls, suggesting a diversity of feeding strategies even at massive sizes. In other words, there wasn’t one ‘best’ skull design for being a predatory giant; several designs functioned perfectly well.”
Rowe and University of Bristol colleague Emily Rayfield tested the strength and function of the skulls using 3D models produced by scanning fossils of 18 different carnivorous dinosaurs. All meat-eating dinosaurs belong to the bipedal group called theropods.
The 3D models were used to measure skull mechanics, feeding performance and bite strength.
Theropods studied ranged in size from the 3m-long Raptorex to the 15m Spinosaurus. They also ranged in age from Herrerasaurus,which lived up to 237 million years ago (mya), to T. rex and Albertosaurus which lived right up until the end-Cretaceous mass extinction 66 mya.
Some dinos like Giganotosaurus (up to 13m long) and Allosaurus (10m long and my favourite dinosaur, for those who are interested) rivalled T. rex for size and were apex predators in their own time and part of the world.
But size didn’t necessarily equate to a powerful bite for these mega-carnivores.
“Tyrannosaurids like T. rex had skulls that were optimised for high bite forces at the cost of higher skull stress,” Rowe says. “But in some other giants, like Giganotosaurus, we calculated stress patterns suggesting a relatively lighter bite. It drove home how evolution can produce multiple ‘solutions’ to life as a large, carnivorous biped.”
“I tend to compare Allosaurus to a modern Komodo dragon in terms of feeding style,” Rowe says. “Large tyrannosaur skulls were instead optimised like modern crocodiles with high bite forces that crushed prey. This biomechanical diversity suggests that dinosaur ecosystems supported a wider range of giant carnivore ecologies than we often assume, with less competition and more specialisation.”
Dinosaur bite illustrations. Credit: Rowe and Rayfield, Current Biology.
Rowe and Rayfield found that larger skull or body size didn’t necessarily equate to a higher bite force. Some larger skulls weren’t appropriately shaped to deal with high stresses, while some smaller theropods like Herrerasaurus (just 6m long) had skulls which could deal with more powerful bites.
“Although cranial biomechanics was not the only factor shaping body size evolution in Theropoda, our results indicate that feeding performance played a key role in determining how different lineages achieved – and sustained – ecological dominance,” Rowe and Rayfield write in their paper.
“These contrasting strategies highlight multiple evolutionary pathways to mega-carnivory and underscore the deep functional diversity that underpinned the success of large-bodied predatory dinosaurs,” they conclude.