/ 23 May 2021

Tiny dinosaur with big eyes and ‘ears’ hunted in the dark

Hunter: Shuvuuia deserti had the same hearing ability as today’s barn owl. Photo: Julius T Csotonyi/ Leemage/AFP

The ability of some dinosaur species to hunt in the dark has long been a question pondered by scientists until it was recently discovered that the sensory adaptations of the small, desert-dwelling, bird-like Shuvuuia deserti enabled it to do so. 

A study led by professor Jonah Choiniere, of the University of the Witwatersrand, found “that many carnivorous theropods such as Tyrannosaurus and Dromaeosaurus had vision optimised for the daytime, and better-than-average hearing presumably to help them hunt”. 

But a tiny theropod, Shuvuuia, the name of which derives from the Mongolian word for bird, is part of a group known as the alvarezsaurus, had both extraordinary hearing and night vision. “The extremely large lagena [the organ that processes incoming sound] of this species is almost identical in relative size to today’s barn owl, suggesting that Shuvuuia could have hunted in complete darkness,” said Choiniere. 

Shuvuuia remains were first discovered in the 1990s. It is estimated to have weighed about two kilogrammes. I had a bird-like skull, long legs and weightlifter arms, all features that might have had a noticeable effect on hunting prey. The Shuvuuia lived in Mongolian deserts about 70-million years ago.

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

The research used computed tomography scanning — a three dimensional scan to zoom in on the ears and eyes of the animals. 

“The late Cretaceous alvarezsauroid Shuvuuia deserti had even further specialised hearing acuity, rivalling that of today’s barn owl. This combination of sensory adaptations evolved independently in dinosaurs long before the modern bird radiation and provides a notable example of convergence between dinosaurs and mammals,” according to the research report.

Choiniere said he was surprised when he saw how long the Shuvuuia’s lagena was because “dinosaur ears weren’t supposed to look like that”. This was after the studies coauthor and palaeontologist James Neenan rushed to tell him that the ear had strangely sized features, which they thought was a mistake until they reconstructed the second ear.

The species was also found to have proportionally larger pupils than in other dinosaurs, which enables more light to enter the eye, allowing for better sight in dark spaces. Researchers used the diameter of the scleral ring to determine the dilation ability of the pupil. 

“Like a camera lens, the larger the pupil can open, the more light can get in, enabling better vision at night. By measuring the diameter of the ring, the scientists could tell how much light in the eye could gather,” according to the study.