It's one of the most memorable moments from the 1993 hit film Jurassic Park: Hot on the trail of a trio of velociraptors, game warden Robert Muldoon finds his prey in the jungle. But as he levels his shotgun at the escaped dinosaur, Muldoon realizes he's walked into a trap.

"Clever girl," quips Muldoon, as a second raptor emerges from the undergrowth to tear him to shreds with her vicious claws.

Velociraptors kept the largest of their three forward-pointing toes raised off the ground as they walked, in order to avoid dulling the blade they used for hunting. But new research, published ahead of the world release of Jurassic World, shows raptors were also capable of using their hunting claws for extra traction.

Tale told by raptor toes

In a new paper published in the journal PaleoWorld, University of Alberta alumnus Lida Xing, University of Alberta PhD student Scott Persons and co-authors write that not all raptor prints show this telltale sign.

At a paleontology site in China, Xing, Persons and their team found a number of tracks with narrow impressions of the raptors' sharp middle toes.

Scott Persons and velociraptor claw

Paleontologist Scott Persons poses with a velociraptor claw, showing the raised middle digit. (Amanda Kelley)

"Because those footprints are preserved in deep, soft, squishy mud … the raptor might have been having a little trouble manoeuvring through that substrate," said Persons.

In order to gain extra traction, hypothesized Persons, the raptors "went ahead and deployed that claw down into the muck. So it was using that claw kind of like a big cleat to help push its way out."

Ancient footprints in China

Their research was based on a series of raptor tracks found at a site in China's Sichuan province. The tracks dating to the Early Cretaceous period are at least 100 million years old. The site is "not so terribly different from the badlands of Alberta," said Persons. 

Although the conditions weren't right for preserving fossilized dinosaur bones, they were perfect for footprints.

The raptors at the Sichuan site would have been the size of a wolf or coyote. Due to their light bone structure, they might have weighed about 14 or 16 kilograms. 

The site includes footprints from all kinds of dinosaurs, ranging from carnivores to vegetarians with long necks.

Jurassic Park and velociraptors

Jurassic Park offered an accurate depiction of raptor footprints, said Persons, even though scientists hadn't yet learned that the dinosaurs kept their middle toes raised. Persons credits Jurassic Park with popularizing the fast-moving dinosaur among children.

"Before that, it was tyrannosaurus rex, triceratops, stegosaurus, brontosaurus," said Persons. "Now, velociraptor is probably the second or third best-known dinosaur."

Since the first Jurassic Park movie, scientists have confirmed that velociraptors were actually covered in fine feathers, rather than scales. But Jurassic World, which comes out on June 12, still depicts velociraptors with scales.