Prehistoric speedway

(Edmonton) A meat-eating dinosaur that terrorized its plant-eating neighbours in South America was a lot deadlier than first thought, a University of Alberta researcher has found.

Carnotaurus, a seven-metre-long eating machine, had a huge tail muscle that U of A paleontology graduate student Scott Persons says made it one of the fastest running hunters of its time.

Persons made a trip to a Los Angeles museum for a close look at a molded copy of a Carnotaurus skeleton. “The caudofemoralis muscle had a tendon attached to the dinosaur’s upper leg bones,” said Persons. “The combination of the muscle size and tendon would have given Carnotaurus’ sturdy legs a highly energized forward motion.”

In earlier research, Persons found a similar tail muscle and leg-power combination in the iconic predator Tyrannosaurus rex. “Up until then, many dinosaur researchers thought T. rex’s huge tail might simply have served as a teeter-totter-like counterweight to its huge, heavy head,” said Persons.

Persons’ examination of Carnotaurus’ tail showed that along its length, long rib-like bones could have supported a huge muscle. Persons used computer simulations to model the caudofemoralis muscle and says the heavy bone structure along the tail presented one drawback. “The tail was rigid, making it difficult for the hunter to make quick, fluid turns,” he said. 

“Imagine yourself as a small plant-eating dinosaur on the floodplains of prehistoric Argentina, and you are unlucky enough to find yourself being charged by a hungry Carnotaurus,” Persons says. “Your best bet is to make a lot of quick turns, because you couldn’t beat Carnotaurus in a straight sprint.”

The study also shows that the specialized tail of Carnotaurus did not appear overnight. Rather, the research documents an evolving sequence of tail shapes beginning in smaller and more ancient South American predators. Persons’ observation challenges previous theories that Carnotaurus was most closely related to large carnivorous dinosaurs from outside South America.

Carnotaurus, a distinctive looking meat-eating dinosaur because of the two horns on its forehead, is getting a lot of media attention. “It was featured the Disney movie Dinosaur, and it appearing in the current television series Terra Nova, which is airing this fall,” said Persons.

Persons published these findings in PLoS ONE on Oct. 14 with supervisor Philip Currie, a paleontology professor at the U of A.