Tyrannosaurus rex, already known colloquially as the king of the dinosaurs, may soon have another title added to its name: champion sniffer.
In the first study of its kind, scientists at the University of Calgary and the Royal Tyrrell Museum in Drumheller, Alta., compared the skulls of a range of prehistoric meat-eating dinosaurs and found that, when it came to a sense of smell, T. rex and its fellow Tyrannosaurs were, indeed, the kings.
The researchers looked at 18 therapods, the group of extinct carnivorous land dinosaurs that includes both T. rex and smaller predators like Velociraptor mongoliensis. They also looked at the primitive bird-ancestor Archaeopteryx and the modern American alligator.
They based their findings on the impressions left in the skulls of the dinosaurs by olfactory bulbs, the part of the brain associated with smell. Even after accounting for the different sizes of the dinosaurs, the Tyrannosaur group of therapods still possessed unusually large olfactory bulbs, suggesting a keen sense of smell, said University of Calgary paleontologist Darla Zelenitsky.
'The anatomical data suggests it was a predator, but it wouldn't have passed on a dead animal if it saw one.' — Darla Zelenitsky, paleontologist
Dromaeosaurids, another group of therapods that includes the velociraptor, also had a relatively strong sense of smell while another group called Ornithomimosaurs, or ostrich dinosaurs, had a relatively low sense of smell.
Zelenitsky and François Therrien, the curator of dinosaur palaeoecology at the Royal Tyrrell Museum, and Yoshitsugu Kobayashi from Hokkaido University in Japan published their findings this week in the British journal Proceedings of the Royal Society B.
T. rex followed nose to food sources
Dinosaur experts have known for some time that T. rex had a good sense of smell, and some have even suggested that its finely tuned sniffer meant it was more likely to have been a scavenger than a predator.
But Zelenitsky said that meat-eating birds alive today are more likely to have large olfactory bulbs compared to their plant-eating kin, so having a keen sense of smell does not necessarily limit the T. rex to scavenging.
She and her co-authors suggest that it may have used its sensitive nose to be active in low-light conditions or to perform certain activities such as locating food sources.
"The anatomical data suggests it was a predator, but it wouldn't have passed on a dead animal if it saw one," she told CBC News.
Sense of smell important to primitive birds
Zelenitsky and her colleagues were also surprised that the Archaeopteryx also seemed to have had a strong sense of smell relative to its size and when compared with modern birds.
"Birds aren't thought to have a keen sense of smell. They are more known for their vision," said Zelenitsky.
It could be that the sense of smell must have remained important to the first primitive birds, she and her co-authors wrote, though Zelenitsky suggested more work was needed to study how dinosaurs' olfactory bulbs compare with living birds.
A quarter of the specimens used in the study were found in Alberta, said Zelenitsky, with the remainder taken from fossil finds all over the world, including Mongolia, China, Madagascar and the United States.