Thescelosaurus neglectus had some very developed senses

Skeleton of the Thescelosaurus neglectus nicknamed Willo (Photo J. Spencer)
Skeleton of the Thescelosaurus neglectus nicknamed Willo (Photo J. Spencer)

An article published in the journal “Scientific Reports” offers new information on the sensory capabilities of the Thescelosaurus neglectus, a small dinosaur that lived just before the great extinction that wiped out non-avian dinosaurs at the end of the Cretaceous period. Paleontologists David Button and Lindsay Zanno submitted a Thescelosaurus skull to a CT scan to reconstruct its interior to create a 3D representation of its brain and inner ear. The conclusion is that this species had some very developed senses, useful for living in burrows.

Thescelosaurus neglectus is a dinosaur species that has been known for a long time, having been identified 110 years ago. Findings of partial skeletons led over the years to the proposal of other species within the genus Thescelosaurus with a lot of arguments. A Thescelosaurus neglectus fossil was interpreted as a heart but subsequent examinations indicated that it was muddy materials that petrified along with the bones.

Studies of Thescelosaurus fossils had already indicated that it was a species that lived in burrows, a characteristic in common with other dinosaurs, not only of the Thescelosauridae group. From an anatomical point of view, for example, it had strong legs suitable for digging. This species was small compared to giant dinosaurs such as some iconic long-necked species but it still had a length that could exceed 3.5 meters and an estimated weight that could exceed 300 kilograms.

Even David Button and Lindsay Zanno thought that this species was plain. However, the CT scan of the skull of the specimen cataloged as NCSM 15728 and nicknamed Willo, the same one involved in the controversy regarding the alleged fossil heart, offered results that led them to change their minds.

A CT scan offers the possibility of reconstructing the inside of a skull and consequently its brain and inner ear. Knowing which parts of the brain were larger indicates which senses were more developed. In the case of Thescelosaurus neglectus, the combination of strengths and weaknesses was unique.

Hearing was Thescelosaurus neglectus’s weak point with severe limitations in the range of frequencies it could hear, only 15% of what the human ear can perceive. It heard high-pitched tones very badly. This is a type of sensory limitation often associated with animals that spend a lot of time underground.

On the contrary, Thescelosaurus neglectus’s sense of smell was excellent. This species’ olfactory bulbs, the brain regions that process smell, are relatively larger than those of any other dinosaur studied so far. Their size is similar to that of alligators, which have an extraordinary sense of smell. For Thescelosaurus neglectus, a developed sense of smell was useful to find underground plants to feed on.

Thescelosaurus neglectus’s sense of balance was also highly developed and allowed it to pinpoint its position in 3D space. That’s another feature often found in burrowing animals.

The evolutionary history of Thescelosaurus neglectus is unclear, and its relationships to other dinosaurs are the subject of debate. This means that this species may have had partial adaptations to digging as an important part of its life or its ancestors had partial adaptations to that type of life. In any case, this study indicates a potential neurological specialization in that lifestyle that could be similar to that of other species of the large group of ornithischian dinosaurs.

This study shows once again how modern technologies can help paleontologists. Understanding which senses were developed and which were weak offers information on evolutionary adaptations and therefore on the type of life that a certain animal led. Lindsay Zanno pointed out that we don’t know the sensory capabilities of most dinosaurs, making it difficult to link these traits to specific lifestyles with confidence, but that also means that there are many interesting discoveries to come.

Artist's concept of a family of Thescelosaurus neglectus in their environment (Image courtesy Anthony Hutchings)
Artist’s concept of a family of Thescelosaurus neglectus in their environment (Image courtesy Anthony Hutchings)

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