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Scientists discover why this dinosaur built like a ‘living fortress’ preferred to live alone

But unlike many dinosaurs of the time, ankylosaurus seemed to prefer a lonesome life.

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(Fabrizio De Rossi / SWNS)

By Chris Dyer via SWNS

An armoured dinosaur built like a 'living fortress' was slow and a loner because it was hard of hearing, scientists discovered.

Ankylosaurus and its close relative the Struthiosaurus austriacus roamed the Earth around the end of the Cretaceous Period - about 68 to 66 million years ago.

But unlike many dinosaurs of the time, ankylosaurus seemed to prefer a lonesome life because of an inferior sense of hearing, researchers found.

Their conclusion comes after a study of the creature's brain case, which gives an idea of its sensory makeup.

The mighty reptile that could grow up to more than 26ft (eight metres) long had a menacing club tail and thick plates of ridges and spikes along the length of its body.

Its close relatives in the nodosaurid family had elongated spikes on their necks and shoulders as well as the same leaf-shaped teeth, but many lacked the mace-like tail clubs of the ankylosaurus.

Fossil braincases, which once housed the brain and other neurosensory tissues, are rare but important for scientists because these structures can give insights into the lifestyle of the animal.

The inner ears can show the auditory capacity and skull orientation.

Remains of a Struthiosaurus austriacus, that lived in Austria, Romania, France and Hungary, were found near Muthmannsdorf, south of Vienna.

The fossils of this dinosaur already belonged to the collection of the Institute for Paleontology in Vienna in the 19th century.

Struthiosaurus austriacus is comparably small, compared to some nodosaurids.

For the study, Marco Schade from the University of Greifswald, Dr Cathrin Pfaff [corr] from the University of Vienna and their colleagues examined the tiny two-inch (50mm) braincase.

It revealed new details of the anatomy and lifestyle of Struthiosaurus austriacus and meant scientists were able to learn more about its sense of balance as well as its hearing or listening abilities.

The results of this study show that Struthiosaurus' brain was very similar to the brains of its close relatives.

For example, the flocculus, an evolutionarily old part of the brain, was very small, the experts said.

The flocculus is important for the fixation of the eyes during motions of the head, neck and whole body, which can be very useful if such an animal was trying to target potential competitors or aggressors.

Marco Schade said: "While many dinosaurs likely lived in groups, at least some ankylosaurs seemed to prefer a lonesome life because of an inferior sense of hearing.

"In contrast to its North American relative Euoplocephalus, which had a tail club and a clear flocculus on the brain cast, Struthiosaurus austriacus may rather relied on its body armour for protection.

"Together with the form of the semi-circular canals in the inner ear, this hints at an exceptionally sluggish lifestyle of this Austrian plant eater."

Researchers also discovered both the Ankylosaurus and the Struthiosaurus austriacus relied on its armour - rather than its hearing - to defend itself from predators.

The authors wrote in their study: "The combination of a relatively short cochlear, the lack of a floccular recess, a short less elaborated nasal passages, the obligate absence of a tail club, but thickened osteoderms [scales] in nodosaurids indicate different ecological adaptations in comparison to ankylosaurids.

"Hence, nodosaurids were possibly less reliant on their sense of hearing, applied a less active style of self-defence and, apparently, occupied different ecological niches than ankylosaurids.

"The new findings of the neuroanatomy of Struthiosaurus austriacus seem to add to this differentiation."

The scientists also found the Struthiosaurus austriacus had the shortest lagena - a part of the inner ear that helps distinguish sounds - of a dinosaur so far examined by experts.

The lagena is the part of the inner ear where hearing takes place and its size can help to indicate the auditory capacities of the animal.

This study delivers new insights into the evolutionary history of dinosaurs and their world, in which Europe was largely submerged in the ocean, the scientists added.

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