A newly published scientific paper, examining the skull of a bird-hipped dinosaur (Thescelosaurus neglectus), suggests that this dinosaur had remarkable senses. CT scans of the skull suggest that this Late Cretaceous herbivore possessed a unique combination of traits and indicate that Thescelosaurus may have spent at least some of the time underground. The study is the first to link a specific suite of sensory abilities with dinosaur behaviour.

If you live alongside Tyrannosaurus rex, then having a burrow or den to hide in might prove to be an effective survival strategy.

Studying the Skull of “Willo”

The skull used in the study comes from “Willo”, which is part of the North Carolina Museum of Natural Sciences vertebrate collection. Thescelosaurus is a member of the Ornithischia. The genus was erected in 1913. It measured around four metres in length and weighed around 340 kilograms. That is about as heavy as a Jersey cow. In an ecosystem which included Triceratops, Edmontosaurus as well as T. rex, Thescelosaurus tends to be overlooked.

Picture credit: Anthony Hutchings

Thescelosaurus neglectus – “Wonderful, Overlooked Lizard”

The binomial scientific name of this dinosaur translates as “wonderful, overlooked lizard”. However, undeterred by this dinosaur’s lack of sharp teeth, dermal armour, crests or horns – traits associated with some of its contemporaries, Dr David Button (Bristol University) began studying Thescelosaurus.

Dr Button built up a detailed, three-dimensional model of the skull using multiple CT scans. The brain and the inner ear were reconstructed. This allowed the researchers to determine the size of the brain and to build up a picture of the dinosaur’s senses.

Dr Button commented:

“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.”

Dr Button added:

“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.”

There is More to Thescelosaurus

Co-author of the paper, published in Scientific Reports, Dr Lindsay Zanno (North Carolina Museum of Natural Sciences), stated:

“The irony is that palaeontologists generally think of these animals as pretty boring. 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.”

Picture credit: Everything Dinosaur

Limited Hearing

The scientists calculated that the hearing range of Thescelosaurus neglectus was extremely limited. It could only hear about 15% of the frequencies humans can detect, and between 4% to 7% of what dogs and cats can hear. In particular, T. neglectus was bad at hearing high-pitched sounds.

Dr Zanno explained:

“We found that Thescelosaurus heard low frequency sounds best, and that the range of frequencies it could hear overlaps with T. rex. 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.”

However, the researchers discovered that this dinosaur did have an excellent sense of smell.

T. neglectus may not have been particularly clever, not even for a dinosaur. It may have had limited hearing, but it had powerful arms and legs, a superb sense of balance and spatial awareness coupled with a keen sense of smell. These are all typical characteristics found in extant vertebrates that spend time underground or engage in digging behaviours.

Dr Button summarised the study:

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

Thescelosaurus neglectus – Not a “Boring” Dinosaur

Dr Zanno concluded:

“We still don’t know the sensory abilities of most dinosaurs. That makes it difficult to link these traits to specific lifestyles with confidence, but it also means there are plenty of cool discoveries to come. The idea that there might have been dinosaurs living under the feet of T. rex and Triceratops is fascinating. No matter what, we now know for certain that T. neglectus isn’t boring.”

Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.

The scientific paper: “Neuroanatomy of the late Cretaceous Thescelosaurus neglectus (Neornithischia: Thescelosauridae) reveals novel ecological specialisations within Dinosauria” by David Button and Lindsay Zanno published in Scientific Reports.

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Scientists have described the first dicraeosaurid sauropod dinosaur known from India. The dinosaur, named Tharosaurus indicus roamed northwestern India during the Middle Jurassic. At around 167 million years old, Tharosaurus indicus represents the earliest diplodocoid dinosaur described to date. It lived at least ten million years earlier than famous North American diplodocids such as Apatosaurus and Diplodocus, to which it was distantly related.

Fragmentary Fossils from Rajasthan

The fragmentary and disarticulated fossils consisting of vertebra and a solitary rib are believed to represent a single animal. The fossils were excavated from shale deposits just north of the village of Jethwai in Rajasthan State. The area is hot and arid, and it is known as the Great Indian Desert or the Thar Desert. The genus name of this new dinosaur references the Thar Desert, in recognition of the location of the fossil finds. The specific name honours the country of origin – India.

The fossil material was excavated from a bedding plane located at the base of the Fort Member (Jaisalmer Formation) with represents an early to middle Bathonian faunal stage deposition.

The Dicraeosauridae

The dicraeosaurids are a clade of small-bodied diplodocoid sauropods classified by their distinctive vertebrae with long paired neural spines. They are both temporally and geographically dispersed with fossils found in Africa, South America as well as China and the USA. The discovery of Tharosaurus extends their temporal range from the Bathonian faunal stage of the Middle Jurassic to the Early Cretaceous.

Picture credit: Everything Dinosaur

The dicraeosaurid illustration (above) is based on the Haolonggood Dicraeosaurus 1:35 scale replica.

To view the range of Haolonggood dinosaur models: Haolonggood Dinosaur Models.

New Insights into Sauropod Diversity

The research team suggest that Tharosaurus indicus is a relic of a sauropod lineage that originated in India and underwent rapid dispersal across the rest of Pangaea. Writing in the academic journal “Scientific Research”, the scientists conclude that this fossil discovery provides new insights into sauropod diversity. It also has important implications for the origin and dispersal of neosauropod dinosaurs.

Tracing the Origins of the Sauropoda

The Sauropoda is thought to have originated in the Late Triassic/Early Jurassic. The origin and radiation of the Neosauropoda and its major clades (Macronaria and the Diplodocoidea) remains contentious. Non-neosauropods were restricted to eastern Gondwana (Zimbabwe and India) and parts of Laurasia (China, Germany and Thailand) during the Late Triassic/Early Jurassic. This suggests that there were barriers preventing their dispersal to the Americas and the most southerly portions of Gondwana. Although preservation and sampling biases cannot be ruled out, neosauropods possibly appeared during the late Early or early Middle Jurassic. The geologically youngest forms being associated with the Americas and Asia.

Tharosaurus indicus – Helping to Clarify Neosauropoda Evolution

Tharosaurus indicus is among the earlier-diverging dicraeosaurid dinosaurs, and its stratigraphic age (Bathonian) makes it the earliest known diplodocoid dinosaur globally. The authors of the paper stress the importance of the Lower and Middle Jurassic deposits of India and propose that further fossil discoveries will help to clarify the evolutionary history of the Neosauropoda.

The scientific paper: “Fossils of the oldest diplodocoid dinosaur suggest India was a major centre for neosauropod radiation” by Sunil Bajpai, Debajit Datta, Pragya Pandey, Triparna Ghosh, Krishna Kumar and Debasish Bhattacharya published in Scientific Reports.

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