Some dinosaurs could once have lived underground, the brain of a 12 foot-long herbivore suggests.
Now a CT scan of its skull has allowed scientists to recreate the dinosaur’s brain – which contained a few surprises.
It turns out, Thescelosaurus had an amazing sense of smell and outstanding balance, but appalling hearing.
Experts say that these traits are associated with living animals that spend at least part of their time underground, and believe this dinosaur’s ancestors may have also done so.
The dinosaur in question, called Willo, is a specimen housed at the North Carolina Museum of Natural Sciences. The dinosaur measured around 12 feet long and weighed around 340kg.
This scientific name roughly translates to ‘wonderful, overlooked lizard’.
‘The irony is that paleontologists generally think of these animals as pretty boring,’ said co-author Dr Lindsay Zanno, of North Carolina University.
‘When we first looked at our results we thought, yeah, this animal is plain as toast.
‘But then we took a big step back and realised there was something unique about the combination of Willo’s sensory strengths and weaknesses.
‘We have strong evidence that Thescelosaurus’s ancestors were semi-fossorial, that is to say they spent part of their time underground.
‘We can’t be sure that Thescelosaurus itself spent time underground as it may have just inherited this particular set of sensory strengths and weaknesses from its ancestors, but we can say for sure it still has adaptations that make it suited for spending time underground.’
Their research also revealed that Thescelosaurus’s hearing range was limited, and they were only able to hear about 15% of the frequencies humans can detect – and between 4% and 7% of what dogs and cats can hear.
In particular, the dinosaur was bad at hearing high-pitched sounds, but they compensated for this lack of hearing with an exceptional sense of smell.
‘We found that Thescelosaurus heard low frequency sounds best, and that the range of frequencies it could hear overlaps with Tyrannosaurs rex,’ said Dr Zanno.
‘This doesn’t tell us they were adapted to hearing T rex vocalise, but it certainly didn’t hurt them to know when a major predator was tooling about in the area.
‘More interesting to us was the fact that these particular deficiencies are often associated with animals that spend time underground.’
The team used a CT scanner to reconstruct soft tissues in Willo’s skull, such as the brain and inner ear.
They then compared these sensory structures to other dinosaurs and their living relatives, allowing the researchers to determine the relative size of Willo’s brain, as well as what her senses of smell, hearing, and balance were like.
Lead author Dr David Button, from Bristol University, said: ‘We found that the olfactory bulbs – the regions of the brain that process smell – were very well developed in Thescelosaurus.
‘They were relatively larger than those of any other dinosaur we know of so far, and similar to those of living alligators, which can smell a drop of blood from miles away.
‘Thescelosaurus may have used its similarly powerful sense of smell to instead find buried plant foods like roots and tubers.
‘It also had an unusually well-developed sense of balance, helping it to pinpoint its body position in 3D space, another trait often found in burrowing animals.’
All of this evidence suggests strongly that the Thescelosaurus neglectus itself may have lived in burrows, and suggests that their ancestors also lived underground.
This work is the first to link a specific sensory fingerprint with this behavior in extinct dinosaurs.
‘The idea that there might have been dinosaurs living under the feet of T. rex and Triceratops is fascinating,’ said Dr Button.
‘No matter what, we now know for certain that Thescelosaurus neglectus isn’t boring.’
The study is published in the journal Scientific Reports.