The ancestors of the little feathered flying friends eating sunflower seeds from your garden inherited a strong sniffer from their ancient flightless dinosaur kin.
Birds, the modern-day descendants of the dinosaurs, were originally thought to have lost much of their sense of smell in the evolutionary race to develop the brain capacity for flight. But scientists at the University of Calgary, the Royal Tyrrell Museum and the Ohio University College of Osteopathic Medicine found that ancient birds' senses of smell actually improved at first.
"It was previously believed that birds were so busy developing vision, balance and coordination for flight that their sense of smell was scaled way back," said Darla Zelenitsky, assistant professor of paleontology at the University of Calgary and lead author of the study published in Proceedings of the Royal Society B.
"Surprisingly, our research shows that the sense of smell actually improved during dinosaur-bird evolution, like vision and balance," said Zelinsky in an Ohio University press release.
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To estimate how strong the ancient birds' sense of smell was in comparison to dinosaurs and modern birds, the scientists examined the skulls of 157 species of dinosaur and bird, both ancient and modern. They looked at the size of the space filled by the olfactory bulb in the skulls. The bigger the space, the better the sense of smell.
"Of course the actual brain tissue is long gone from the fossil skulls," said co-author Lawrence Witmer, professor of paleontology at the Ohio University College of Osteopathic Medicine, "but we can use CT scanning to visualize the cavity that the brain once occupied and then generate 3D computer renderings of the olfactory bulbs and other brain parts."
The researchers found that ancient birds even outdid their dinosaur cousins in the ability to sniff out a meal or a mate, or to catch the nasty scent of a lurking predator.
"The oldest known bird, Archaeopteryx, inherited its sense of smell from small meat-eating dinosaurs about 150 million years ago," said co-author François Therrien, curator of dinosaur palaeoecology at the Royal Tyrrell Museum. "Later, around 95 million years ago, the ancestor of all modern birds evolved even better olfactory capabilities."
Dinos and birds showed similarities and differences in their need for a sense of smell. The scientists noted that Archaeopteryx and pigeons had similar senses of smell.
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"Turkey vultures and albatrosses are birds well known for their keen sense of smell, which they use to search for food or navigate over large areas," says Zelenitsky. "Our discovery that small Velociraptor-like dinosaurs, like Bambiraptor, had a sense of smell as developed as turkey vultures and albatrosses, suggests that smell may have played an important role while these dinosaurs hunted for food."
But many birds that humans see on a day-to-day basis, like crows and pet parrots, don't have particularly sensitive sniffers. Zelenitsky thinks it may be no coincidence that they are also some of the smartest birds. Perhaps smarter birds need less powerful noses, she said.
There were big differences in dino noses as well. Predators, like T. rex, had large olfactory bulbs most likely for tracking prey, finding carrion, and other uses, like finding distant mates and guarding territory, said Therrien. Triceratops, on the other hand, had little room in its horn-covered head for smelling equipment.
IMAGE 1: Evolution in birds of the olfactory bulb, the part of the brain where smell information is processed, passing from a dinosaur (Bambiraptor) through early birds (Lithornis, Presbyornis) to a modern-day bird (pigeon). (Credit: WitmerLab at Ohio University).
IMAGE 2: Graph of olfactory bulb size and body size of individual bird (black symbols) and dinosaur (green symbols) species. Similarities in olfactory bulb size and body size between species, as illustrated by the dinosaur Bambiraptor, the turkey vulture and the albatross, suggest a comparable sense of smell. Courtesy of Darla Zelenitsky.
IMAGE 3: The dinosaur Bambiraptor in a turkey vulture's colors. Bambiraptor had a keen sniffer similar to that of a modern-day turkey vulture. Courtesy of Julius Csotonyi.
IMAGE 4: T. rex skeleton (Wikimedia Commons).
Tags: Dinosaurs, Feathered Dinosaurs, Paleontology, Prehistoric Animals
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