EDMONTON — A University of Alberta study of leg length in meat-eating dinosaurs has found they evolved longer limbs so they could run faster and catch their prey.
Doctoral student Scott Persons says he and his supervisor Philip Currie collected measurements from more than 50 different species of predatory dinosaurs ranging in size from smaller than a chicken to longer than a school bus.
“How fast a predator can run is obviously important,” said Persons, who led the study as part of his doctoral research.
“Speed determines what prey you can catch, how you hunt it, and the sort of environment that you are most successful in.”
He said results indicate early dinosaur meat-eaters were generally slower, but evolved to become faster over time. A key example is the Tyrannosaurus rex, which developed legs much longer than expected.
“You can be a big scary thing but if you can’t get close enough to bite onto another animal it’s no good to you. Tyrannosaurus rex was certainly faster than some of the big, bulky herbivores but its number 1 food source was probably the faster animals like duck-billed dinosaurs it needed to be able to catch,” he said.
“There is a general trend throughout the evolution of meat-eating dinosaurs favouring high-speed running,” Persons said. “Now maybe that’s because of a predator-prey arms race. Maybe they’re evolving alongside some plant-eating dinosaurs that are also evolving for high speeds.”
Persons said fast-running animals have longer legs from the knee down. The longer the lower leg in comparison to the upper leg, the faster the animal is.
The five-metre-long Nanotyrannus leads the pack when it comes to evolution, leaving T. rex in the dust.
Persons said Nanotyrannus’ status as a distinct species has been debated for years due its strong resemblance to a juvenile T. rex, but its uniquely elongated limbs now indicate it was.
“In terms of Cretaceous ecology, T. rex was the lion and Nanotyrannus was the cheetah. As far as I’m concerned, it was the scariest dinosaur,” said Persons.
“Sure, it might take it four to five bites to eat you, while T. rex could do it in just one or two, but eaten is eaten–and no dinosaur was better adapted to chase you down.”
The new research was published this week in the peer-reviewed journal Scientific Reports.