New research demonstrates that the brain of Thescelosaurus neglectus, a small plant-eating neornithischian dinosaur that lived just before the end-Cretaceous mass extinction event, was relatively small compared to most other neornithischians, suggesting cognitive capabilities within the range of living reptiles. Other traits include a narrow hearing range, with limited ability to distinguish high frequencies, paired with an unusually well-developed sense of smell (olfaction) and vestibular sensitivity.
Thescelosaurus neglectus lived in what is now North America just before the end-Cretaceous mass extinction, around 66 million years ago.
This dinosaur was a small (3.6 m, or 11.8 feet, in length) but heavy (340 kg) herbivore.
In the new research, paleontologists David Button and Lindsay Zanno used a CT scanner to reconstruct soft tissues in the skull of Thescelosaurus neglectus — such as the brain and inner ear — that were lost to the fossilization process.
Comparing these sensory structures to other dinosaurs and their living relatives allowed the researchers to determine the relative size of the dinosaur’s brain, as well as what her senses of smell, hearing, and balance were like.
“The irony is that paleontologists generally think of these animals as pretty boring,” said Dr. Zanno, a paleontologist 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 plain as toast. But then we took a big step back and realized there was something unique about the combination of the dinosaur’s sensory strengths and weaknesses.”
The researchers determined that Thescelosaurus neglectus’ hearing range was limited.
The dinosaur could only hear about 15% of the frequencies humans can detect, and between 4 and 7% of what dogs and cats can hear.
In particular, Thescelosaurus neglectus was bad at hearing high-pitched sounds.
“We found that Thescelosaurus neglectus…
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