CT scan reveals ‘neglected’ dinosaur had super senses

A CT scan of the skull of an often-overlooked herbivorous dinosaur shows that while it wasn’t all that ‘intelligent’, it had a unique combination of traits associated with living animals that spend at least part of their time underground , including a super sense of smell and excellent balance. The work is the first to link a specific sensory fingerprint to this behavior in extinct dinosaurs.

The dinosaur in question, Willo, is a specimen housed in the North Carolina Museum of Natural Sciences. Willo is a Thescelosaurus neglect – a small (3.6 meters long) but heavy (340 kilograms) herbivore that lived in what is now North America just before the mass extinction at the end of the Cretaceous period, 66 million years ago.

Willo’s scientific name roughly translates to “beautiful, overlooked lizard.” But David Button, a former Brimley Postdoctoral Scholar at the North Carolina Museum of Natural Sciences and North Carolina State University, decided to take a closer look at the skull of this “overlooked” dinosaur. Button is currently a research associate at the University of Bristol in Great Britain

Button used a CT scanner to reconstruct soft tissues in Willo’s skull, such as the brain and inner ear, that had been lost to the fossilization process. By comparing these sensory structures to other dinosaurs and their living relatives, the researchers were able to determine the relative size of Willo’s brain, as well as what her senses of smell, hearing and balance were like. The research was published in Scientific reports.

“The irony is that paleontologists generally consider these animals to be quite boring,” says Lindsay Zanno, associate professor at NC State, chief of paleontology at the North Carolina Museum of Natural Sciences, and co-author of the work. “When we first looked at our results, we thought, yeah, this animal is as plain as toast. But then we took a big step back and realized there was something unique about the combination of Willo’s sensory strengths and weaknesses .”

Button and Zanno determined that the hearing range of T. negerus was limited. The dinosaur could only hear about 15% of the frequencies that humans can hear, and between 4% and 7% of what dogs and cats can hear. T. negerus in particular was poor at hearing high-pitched sounds.

“We found that Thescelosaurus heard low frequencies best, and that the range of frequencies it could hear overlapped with those of T. rex,” says Zanno. “This doesn’t mean they were adapted to hearing T. rex’s voice, but it certainly didn’t hurt them to know when a large predator was prowling in the area. More interesting to us was the fact that this specific deficiencies often associated with animals that spend time underground.”

Thescelosaurus balanced its poor hearing with an excellent sense of smell.

“We found that the olfactory bulbs – the brain areas that process smell – were very well developed in Thescelosaurus,” says Button. ‘They were relatively larger than those of any other dinosaur known to date, and comparable to those of living alligators, which can smell a drop of blood from miles away. Thescelosaurus may have used its equally powerful sense of smell to find buried plant foods such as roots and tubers instead. It also had an unusually well-developed sense of balance, which allowed it to determine its body position in 3D space, another trait often found in burrowing animals. ”

The poor cognitive and hearing abilities of T. negerus, coupled with powerful arms and legs and overdeveloped senses of smell and balance, are all traits typical of animals that today spend time underground and/or engage in digging behavior.

“While we can’t say definitively that these animals lived part of their lives underground, we do know that their ancestors did,” Button says. “This fact, together with their unique combination of sensory abilities, strongly suggests that T. negusus engages in similar behaviors.”

“We still don’t know the sensory capabilities of most dinosaurs,” Zanno says. “That makes it difficult to confidently link these traits to specific lifestyles, but it also means that there are plenty of cool discoveries to come.

“The idea that dinosaurs might have lived under the feet of T. rex and Triceratops is fascinating. Either way, we now know for sure that T. negusus isn’t boring.”