A study comparing how carnivorous dinosaurs tore through their meat has found meat eaters munched using at least four distinct biting methods.
The findings, by UK palaeontologist Dr Manabu Sakamoto from the University of Bristol, appear today in the Proceedings of the Royal Society B.
Sakamoto compared 41 species of theropods - a group of upright dinosaurs that include Tyrannosaurs - to determine their 'biting performance' and how this differed over time. Theropod also includes the smaller more primitive coelophysoids and the bird-like Archaeopteryx.
To differentiate each dinosaur's biting performance, Sakamoto measured the ratio of the length of the dinosaur's tooth row to the muscle arrangements of their jaws.
Unsurprisingly, his results confirm that how dinosaurs chomped was dictated by the shape of their skull.
Specialised biters like the coelophysoids, which have slender, narrow jaws had a biting style that was highly efficient at the back of the tooth row, but very swift at the tip of the snout.
Big biters like Tyrannosaurus had a more consistent biting performance along the entire tooth row.
Velociraptor, one of the scary beasts made popular by the movie Jurassic Park, had a "weak/fast style", biting rapidly but inefficiently, Sakamoto says.
"Perhaps biting styles are conserved by other cranial traits, such as the size of the skull and relative proportions of the different elements of the skull - for instance the size and position of the eyes or nasal cavity," says Sakamoto.
Once a biting style evolved, it doesn't appear to have changed much over time until there was an opportunity to adapt, such as when a group of dinosaurs radiated quickly to fill empty evolutionary niches, he says.
"This sort of evolutionary change is frequently observed after a crisis that leaves many ecological niches empty," says Sakomoto.
Australian palaeontologist Dr Steve Salisbury says while the research confirms what palaeontologists had already suspected, one surprise was the specialised biting style of the primitive coelophysoids.
"You would assume that some of the earliest theropods such as coelophysoids would have a more generalised biting performance and later [species] would have had a more specialised biting performance, but this is not what he's found," says Salisbury, who is from the University of Queensland in Brisbane.
Salisbury says the research is a "good way to compare different ideas" that palaeontologists have about theropod feeding behaviour.
"This is a way of testing [these ideas] mathematically, and it's a relatively simple way of assessing biting performance. I'm surprised it hasn't been done before."