This illustration shows Struthiosaurus austriacus, a "living fortress" dinosaur that lived 80 million years ago in Austria.

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Life as a “living fortress” was a lonesome one for this dinosaur. A heavily armored nodosaurid, which sported elongated spikes on its neck and shoulders, was likely a sluggish loner who couldn’t hear very well, according to a new study.

Researchers studied the braincase of the 80 million-year-old herbivorous dinosaur, which was related to the famously club-tailed ankylosaurs.

The fossil of Struthiosaurus austriacus was first discovered in Austria and has been in the collection of the Institute for Paleontology in Vienna since the 1800s.

While some of these lumbering, tank-like ankylosaurs could reach up to 26 feet (8 meters) in length, Struthiosaurus was relatively small at 8.8 feet (2.7 meters) long.

In order to better understand the hearing and equilibirum of this ironclad dinosaur, researchers analyzed the small 1.9-inch (50-millimeter) braincase, using a micro-CT scanner to create a digital 3D cast. While the brain tissue of a dinosaur was too fragile to preserve, the structure of its braincase can reveal aspects of a dinosaur’s lifestyle.

The findings published last week in the journal Scientific Reports.

What the braincase revealed

This dinosaur had a very small flocculus, a part of the brain key to eye fixation when the head, neck or body is in motion – especially when targeting competitors or predators. The finding, combined with the semicircular shape of its inner earl canals, suggests this dinosaur moved very slowly. Rounded ear canals allow for more sensitivity than semicircular ones that might disrupt the flow of vibrations and nerve impulses, according to the researchers.

In life, this animal would have been very passive and sluggish, rather than acting as an aggressor, and could “take care of itself in order to survive,” said study author Marco Schade, a paleontologist at the University of Greifswald in Germany. The dinosaur wasn’t blind and would have been able to see predators coming.

“While some of its relatives probably defended themselves with their tail clubs, Struthiosaurus probably relied more on its distinctive armouring (for protection),” employing a passive style of self-defense, Schade said in a statement.

“Apart from this, carnivorous dinosaurs very likely tended to hunt silently, which is the opposite from their depiction as theme park monsters in ‘Jurassic Park,’” he said.

The braincase also revealed the shortest ever cochlea found in a dinosaur. The cochlea is part of the inner ear where hearing takes place, and its size can determine hearing ability.

“These observations agree with an animal that adapted to a comparatively inactive lifestyle with limited social interactions,” the study authors wrote.

No social butterfly

Scientists believe that many dinosaurs lived and traveled in groups, but this species of ankylosaur likely lived as a loner due to its poor hearing. Struthiosaurus could be found munching on low-growing plants in coastal areas and had a stronger bite force to chew through tough vegetation.

“The animal’s hearing was obviously not well developed and so, if necessary, Struthiosaurus communicated with (others) in a way other than vocalizations,” said study coauthor Cathrin Pfaff, a research associate and head of the micro-CT facility at the University of Vienna’s Institute for Paleontology, in a statement.

However, Struthiosaurus “was not completely unable to listen to others,” Schade said, and like modern turtles, probably only used sound to communicate when absolutely necessary.

“Paleontologists are not inclined to think that ankylosaurs in general were particularly gregarious animals, but since sound-based intraspecific communication is a popular means among animals, the somewhat constrained auditory capabilities of nodosaurids may suggest that they did not appreciate too much company or the full frequency range of complex classical music,” Schade wrote via email.

Next, the researchers want to take a closer look at the braincases of other European ankylosaurs to see if these findings are unique to one species, or if they represent something that other relatives evolved.