It’s a beautiful, sunny day in the Late Cretaceous. Two dinosaurs take their places at the start line, ready to race. It’s time to place your bet — who will win, the tyrannosaur or the hadrosaur? It seems like a totally unfair race: the mighty tyrannosaur (wearing No. 1), one of the most awe-inspiring predators to walk the Earth, up against the loveable but clownish hadrosaur. But looks can be deceiving.
Illustrations by Niroot Puttapipat
Scott Persons, ’11 MSc, a University of Alberta PhD student, has made a study of the tails and leg structure of both predator and prey, and he’s come up with some surprising conclusions about who might cross the finish line first. So before you decide whether you’re on Team Tyrant or Team Duck, Persons offers a few facts to help you calculate the odds.
A LEG UP
The first thing to know is that tyrannosaurs were bipedal. Hadrosaurs were mostly quadrupeds, but when they needed to run, they could stand up on their strong back legs for more speed.
So the first clue to who would win the race is in the metatarsals — bones that in humans are part of the feet but in a dinosaur form the lower part of the leg. The Tyrannosaurus (above left) has long metatarsals, while the Edmontosaurus, a type of hadrosaur, has metatarsals that are much shorter.
Advantage: tyrannosaur. Longer legs mean longer steps.
Mammals tend to have skinny tails that aid in balance, climbing or swatting away flies. But reptiles have an additional use for their tails: they’re a powerhouse that helps move the whole animal, thanks to a large muscle called the caudofemoralis. Persons realized that dinosaurs also had these muscles. Though the muscles themselves weren’t part of the fossils, he found signs of their existence in the points of muscle attachment on dinosaurs’ femurs as well as the bone structures in their tails. This was evidence that dinosaurs could run much more quickly than paleontologists had previously believed.
Advantage: No advantage here — both dinos get a speed boost thanks to the caudofemoralis.
LONG AND SHORT OF IT
There is a difference between the tyrannosaur femurs and those of the hadrosaurs. On the Albertosaurus, a tyrannosaur, the attachments were high on the leg, allowing the tyrannosaur to take long, powerful strides. But on the Lambeosaurus, a hadrosaur, the muscle was attached much lower down, forcing it to take shorter steps because the lower point of attachment would limit how far its leg would swing. This shorter stride gave the hadrosaur a lot more leverage, making it a more efficient runner.
Advantage: None. The hadrosaur’s efficiency more than balances out the bigger dino’s speed.
AND THE WINNER IS ...
Now that you’ve seen the evidence, can you guess who would win the race? The answer depends on how far they run.
The sprint champ: tyrannosaur. Like a cheetah, the tyrannosaur was designed to move fast and take down its prey very quickly. It would tire out after a short sprint, but, ideally, it would be settling down for a tasty meal after a burst of speed.
The distance runner: hadrosaur. Like a zebra, the hadrosaur’s survival strategy was to keep running long after the tyrannosaur had tired out and stopped pursuit. And unlike a zebra, the hadrosaur had a lot more time to see its predator coming; it’s a lot easier to spot a dinosaur than a big cat sneaking through grass.