A study published this month in “Scientific Research” suggests that the Late Cretaceous European nodosaurid Struthiosaurus was not the most active of dinosaurs and probably not the most social. Analysis of the single, partial braincase (IPUW 2349/6) of S. austriacus has permitted scientists to gain a better understanding of this armoured dinosaur’s senses. The conclude that the short semi-circular canals and the shortest cochlear duct described from dinosaur fossils known to date, indicate that Struthiosaurus led a rather inert, sedentary life and compared to other members of the Dinosauria, it was comparatively inactive with limited social interactions.

The researchers calculate that Struthiosaurus had poor hearing and it probably relied on a less active style of self-defence compared to their tail club swinging relatives the ankylosaurids.

An illustration of the Late Cretaceous nodosaurid Struthiosaurus austriacus from Austria. A study of this dinosaur’s braincase suggests that it was relatively inert, sluggish and partially deaf. Picture credit: Fabrizio De Rossi.

Picture credit: Fabrizio De Rossi

Sluggish and with Limited Hearing

Researchers from the University of Vienna in collaboration with a colleague from the University of Greifswald in Germany subjected the partial braincase of S. austriacus to CT scans. From this information, three-dimensional models of the 5 cm wide braincase of this dinosaur were created.

The braincase consists of several fused skull bones that housed the brain and other neurosensory tissues. Analysis of the structures preserved can provide palaeontologists with information about the sensory capabilities of the animal and more fundamental details of anatomy such as the angle at which the animal held its head.

Photographs (C,D,G,J) and photogrammetric models (E,F,H,I,K) created from the CT scans of the holotype specimen of Struthiosaurus austriacus, (IPUW 2349/6). Right lateral view (C,E), (D,F) left lateral, (I) anterior, (J,K) ventral and (G,H) posterior views. Note scale bar = 2 cm. Picture credit: Schade et al.

Picture credit: Schade et al

The results of this study of the braincase of Struthiosaurus indicate that its brain was very similar to the brains of other nodosaurids. For example, the flocculus, an ancient part of the tetrapod brain, associated with co-ordination and motor skills was very small. Ankylosaurs with their large tail clubs, such as Euoplocephalus had a proportionately larger flocculus. A bigger flocculus might have helped ankylosaurs to co-ordinate their defensive strikes with their powerful tail clubs.

In addition, the team which included Marco Schade (University of Vienna), plotted the auditory capacity of Struthiosaurus and calculated that its hearing range was rather limited (between 296 and 2164 Hz). In contrast, humans on average have a much broader frequency of hearing range – around 31 Hz to 19,000 Hz.

Location of the Struthiosaurus austriacus fossil finds in Austria (A). To date three species of Struthiosaurus have been scientifically described, S. transylvanicus from Maastrichtian-aged deposits or Romania, S. languedocensis from the early Campanian of France and S. austriacus which was described from fragmentary fossil material including a partial braincase discovered during coal mining operations near the town of Muthmannsdorf (early Campanian Grünbach Formation). The type locality of S. austriacus is marked by the star. Scale drawing of S. austriacus from Fabrizio De Rossi. Picture credit: Schade et al.

Picture credit: Schade et al

Nodosaurids Occupied a Different Ecological Niche

Both nodosaurids and their close relatives, the ankylosaurids were lumbering, heavily armoured animals adapted to low browsing. Although postcranial fossils are quite similar, there is a growing body of evidence to indicate marked differences between these two types of dinosaur. Nodosaurids may have preferred coastal or floodplain environments and may have evolved stronger jaws to give them a more powerful bite, an adaptation to processing tough vegetation. Gut contents associated with nodosaurids such as Borealopelta markmitchelli, suggest they were selective feeders: Borealopelta was a Fussy Eater.

This study suggests that for Struthiosaurus at least the combination of a relatively short cochlear duct, a reduced flocculus, less elaborate nasal passages and the absence of a tail club but with heavily reinforced dermal armour suggests that nodosaurids had different ecological adaptations when compared to ankylosaurs.

The researchers postulate that nodosaurids were possibly less reliant on their sense of hearing, had a less active style of self-defence and may have occupied different ecological niches than ankylosaurids.

Struthiosaurus may have lived alone and may not have moved in social groups.

The recently introduced Isaac the Sauropelta model depicts the typical armour and spikes of a nodosaur. These dinosaurs may have been relatively slow moving, with a limited sense of hearing but they would have represented a formidable adversary for a younger theropod.

The scientific paper: “Neuroanatomy of the nodosaurid Struthiosaurus austriacus (Dinosauria: Thyreophora) supports potential ecological differentiations within Ankylosauria” by Marco Schade, Sebastian Stumpf, Jürgen Kriwet, Christoph Kettler and Cathrin Pfaff published in Scientific Reports.

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New research into the musculature of the early sauropodomorph Thecodontosaurus antiquus has helped scientists to understand the evolutionary transition from agile bipeds to super-sized quadrupedal sauropods. Writing in the open-access, on-line journal “Royal Society Open Science”, scientists from the University of Bristol have reconstructed the limb musculature of Thecodontosaurus. Their reconstruction shows that this Late Triassic dinosaur was an agile, biped but it already had some anatomical adaptations which would permit its descendants to grow to huge sizes.

Thecodontosaurus fossil block with life reconstruction in the background. Picture credit: Simon Powell/University of Bristol.

Picture credit: Simon Powell/University of Bristol

Bristol’s Dinosaur

Thecodontosaurus (T. antiquus) fossils are known from Upper Triassic rocks exposed around the city of Bristol in England. During the Late Triassic, this region consisted of an archipelago surrounded by a warm tropical sea. Hundreds of fragmentary fossils representing many individuals are known, most of these fossils are housed at the Bristol City Museum and Art Gallery. Thecodontosaurus is believed to have measured up to 2.5 metres in length, however, its long, thin tail made up more than 50% of its entire body length.

It weighed around twenty kilograms, but it was part of the Sauropodomorpha clade of lizard-hipped dinosaurs that were to evolve into giants during the Jurassic and Cretaceous. Famous dinosaurs such as Diplodocus and Brachiosaurus from the Jurassic as well as Cretaceous leviathans such as Patagotitan and Alamosaurus.

Thecodontosaurus

Thecodontosaurus was the first Triassic genus of dinosaur to be named and described (1836).

Researchers have examined tell-tale muscle scars associated with Thecodontosaurus limb bones to reconstruct the musculature of this Late Triassic dinosaur. Picture credit: Gabriel Ugueto.

Picture credit: Gabriel Ugueto

Lead author of the paper, PhD student at the University of Bristol Antonio Ballell commented:

“The University of Bristol houses a huge collection of beautifully preserved Thecodontosaurus fossils that were discovered around Bristol. The amazing thing about these fossilised bones is that many preserve the scars and rugosities that the limb musculature left on them with its attachment.”

These features on the bones permit palaeontologists to infer the shape, size and anatomical position of the musculature of the animal. For example, the muscles associated with the limbs can be reconstructed and the dinosaur’s anatomy can be further refined by comparing the computer models generated with the anatomy of extant relatives such as crocodiles and birds.

Co-author of the study Professor Emily Rayfield (University of Bristol), added:

“These kinds of muscular reconstructions are fundamental to understand functional aspects of the life of extinct organisms. We can use this information to simulate how these animals walked and ran with computational tools.”

Palaeontologists Continuing to Learn from Thecodontosaurus Fossils

Thecodontosaurus was one of the first dinosaurs to be formally named and described but palaeontologists can still learn a lot from its fossils. For example, thanks to the considerable volume of T. antiquus material, the research team were able to build the entire forelimb and hindlimb musculature. This is the first time scientists have been able to reconstruct the limb musculature of an early-branching sauropodomorph.

The analysis of the limb muscles of T. antiquus confirm that it was a fast-running, agile biped. The forelimbs were probably not used in locomotion but were very effective at grasping objects such as potential prey. The anatomy of the lithe Thecodontosaurus is in stark contrast to the later sauropods which became obligate quadrupeds.

The researchers determined that key traits of later sauropod-line dinosaurs had already evolved in this early genus.

“From an evolutionary perspective, our study adds more pieces to the puzzle of how the locomotion and posture changed during the evolution of dinosaurs and in the line to the giant sauropods. How were limb muscles modified in the evolution of multi-ton quadrupeds from tiny bipeds? Reconstructing the limb muscles of Thecodontosaurus gives us new information of the early stages of that important evolutionary transition.”

The enormous body of the titanosaur dwarfs visitors. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

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

The scientific paper: “Walking with early dinosaurs: appendicular myology of the Late Triassic sauropodomorph Thecodontosaurus antiquus” by Antonio Ballell, Emily J. Rayfield and Michael J. Benton published in Royal Society Open Science.

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