Researchers unveil the oldest spinosaur brains

Researchers from the University of Southampton and Ohio University have reconstructed the brains and inner ears of two British spinosaurs, helping to uncover how these large predatory dinosaurs interacted with their surroundings.

Spinosaurs are an unusual group of theropod dinosaurs, endowed with long, crocodile-like jaws and conical teeth. These adaptations helped them lead a somewhat aquatic lifestyle, stalking riverbanks in search of prey, including large fish. This way of life was very different from that of more familiar theropods such as Allosaurus and Tyrannosaurus.

To better understand the evolution of spinosaur brains and senses, the team scanned fossils of Baryonyx from Surrey and Ceratosuchops from the Isle of Wight. These two are the oldest spinosaurs for which braincase material is known. The giant creatures would have roamed the planet about 125 million years ago. The braincases of both specimens are well preserved, and the team digitally reconstructed the inner soft tissues, which had long since decomposed.

The researchers found that the olfactory bulbs that process smells weren’t particularly developed and the ear was probably tuned in to low-frequency sounds. The parts of the brain involved in keeping the head stable and focusing on prey may have been less developed than in later, more specialized spinosaurs.

The results will be published in Journal of Anatomy.

“Despite their unusual ecology, the brains and senses of these early spinosaurs appear to share many aspects with those of other large-bodied theropods – there is no evidence that their semi-aquatic lifestyle is reflected in the way their brain organizes.” is,” he said University of Southampton Ph.D. Student Chris Barker, who led the study.

One interpretation of this evidence is that spinosaurs’ theropod ancestors already possessed brains and sensory adaptations suited to part-time fishing, and that spinosaurs only needed to evolve an unusual snout and teeth to adapt to a semi-aquatic existence specialize.

“Because the skulls of all spinosaurs are so specialized for fishing, it is surprising to see such ‘unspecialized’ brains,” said contributing author Dr. Darren Naish. “But the results are still significant. It’s exciting to learn so much information about sensory abilities – hearing, smell, balance and so on – from British dinosaurs. With state-of-the-art technology, we’ve gotten basically all the brain-related information we could possibly get from these fossils,” said Dr. Naish.

In recent years, the EvoPalaeo Lab at the University of Southampton has been conducting extensive research into new spinosaurs from the Isle of Wight. Ceratosuchops itself was only announced by the team in 2021, and its discovery was followed in 2022 by the release of another new spinosaur – the giant White Rock spinosaur. Ceratosuchops’ braincase was scanned at the μ-Vis X-ray Imaging Center at the University of Southampton, home to some of the country’s most powerful CT scanners, and a model of its brain is displayed alongside its bones at the Dinosaur Isle Museum in Sandown on the Isle of wight issued.

“This new research is just the latest in a revolution in paleontology due to advances in CT-based imaging of fossils,” said co-author Lawrence M. Witmer, professor of anatomy at Ohio University’s Heritage College of Osteopathic Medicine. who has been performing CT scans of dinosaurs – including Baryonyx – for over 25 years. “We are now able to assess the cognitive and sensory abilities of extinct animals and explore how the brains evolved in behaviorally extreme dinosaurs like spinosaurs.”

“This new study highlights the significant role British fossils play in our ever-evolving, fast-paced understanding of dinosaurs and shows how Britain – and the University of Southampton in particular – is at the forefront of spinosaur research,” said Dr. Neil Gostling, who runs the University of Southampton’s EvoPalaeoLab. “Spinosaurs themselves are one of the most controversial of all dinosaur groups, and this study is a valuable addition to the ongoing discussions about their biology and evolution.”