Dinosaurs may have passed on to owls their ability to stalk at night.

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An artistic rendering imagines how the nocturnal dinosaur Shuvuuia might have chased down insects in the Mongolian desert during the Late Cretaceous. Photo by Viktor Radermaker

According to new findings, a small bird-like dinosaur’s precise night vision and owl-like hearing helped it to hunt down prey in the dead of night.

Nocturnal hunting is uncommon for predators because it necessitates advanced sensory abilities; many of the strongest night-hunters are birds, such as owls, nightjars, nighthawks, and others.

Since modern birds are the dinosaurs’ nearest living kin, scientists historically hypothesised that owls and other nocturnal birds retained their theropod ancestors’ night-hunting skills.

 

To investigate the possibility, scientists used detailed CT scans to compare the anatomical features of the eyes and inner ears of nearly 100 living bird and extinct dinosaur species.

They shared the results of the analysis in a new paper, published Thursday in the journal Science.

Researchers contrasted the duration of the lagena, the duct responsible for processing incoming sound input, in the ears. The barn owl, one of the most skilled hunters of the night, has the longest lagena compared to body size of birds.

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The scale of the scleral band, the bone or set of bones that surrounds the pupil and supports the eyeball, was studied in the eyes.

Scleral circles with greater diameters lead to larger pupils. The more light a pupil can let in, the wider it can open. Animals with particularly large pupils can see best in the dark.

 

The survey of dinosaur fossils showed Tyrannosaurus and Dromaeosaurus enjoyed powerful hearing, however, the shape and size of their eyes suggested the vision of carnivorous theropods was best suited for daytime.

However, researchers found the lagena and scleral ring of a small theropod named Shuvuuia, member of a group of long-legged dinosaurs called alvarezsaurs, were most similar to those of the barn owl.

“As I was digitally reconstructing the Shuvuuia skull, I couldn’t believe the lagena size … I called Prof. Choiniere to have a look,” joint first author James Neenan said in a news release.

“We both thought it might be a mistake, so I processed the other ear — only then did we realize what a cool discovery we had on our hands!” said Neenan, a researcher with the Oxford University Museum of Natural History.

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“I couldn’t believe what I was seeing when I got there — dinosaur ears weren’t supposed to look like that!” said first author Jonah Choiniere, a professor of comparative palaeobiology at the University of the Witwatersrand in South Africa.

Shuvuuia populated the Mongolian desert during the Cretaceous Period. The chicken-sized theropod featured a slender head, short feathers, stubby arms and long, roadrunner-like legs that were optimized for digging.

Scientists suspect Shuvuuia rooted out small mammals and insects from their burrows before chasing them down in the black of night.

“Nocturnal activity, digging ability, and long hind limbs are all features of animals that live in deserts today,” said Choiniere, “but it’s surprising to see them all combined in a single dinosaur species that lived more than 65 million years ago.”

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