Researchers from the University of Southampton and the University of Ohio have reconstructed the brains and inner ears of two British spinosaurs, helping to uncover how these large predatory dinosaurs interacted with their environment.
Spinosaurs are an unusual group of theropod dinosaurs, equipped with long, crocodile-like jaws and conical teeth. These adaptations helped them live a somewhat aquatic lifestyle that involved stalking the banks in search of prey, including large fish. This way of life was very different from that of the more familiar theropods, such as Allosaurs et Tyrannosaurus.
To better understand the evolution of spinosaur brains and senses, the team scanned fossils of Baryonyx of Surrey and Ceratosuchops from the Isle of Wight. These two are the oldest spinosaurs for which puzzle material is known. The huge creatures are said to have roamed the planet around 125 million years ago. The braincases of both specimens are well preserved, and the team digitally reconstructed the internal soft tissues that had long decayed.
The researchers found that the olfactory bulbs, which process smells, were not particularly developed and that the ear was probably adapted to low-frequency sounds. The parts of the brain involved in maintaining head stability and fixed gaze on prey may have been less developed than they were in later, more specialized spinosaurs.
The conclusions must be published in the Anatomy Journal.
“Despite their unusual ecology, it appears that the brains and senses of these early spinosaurs retained many aspects in common with other large theropods – there is no evidence that their semi-aquatic lifestyle is reflected in the way their brains are organised,” said Chris Barker, a PhD student at the University of Southampton, who led the study.
One interpretation of this evidence is that the theropod ancestors of spinosaurs already possessed brains and sensory adaptations suitable for part-time fish-catching, and that “all” spinosaurs had to do to specialize for a semi-aquatic existence was develop. an unusual muzzle and teeth.
“Because the skulls of all spinosaurs are so specialized for catching fish, it’s surprising to see such ‘unspecialized’ brains,” said contributing author Dr. Darren Naish. “But the results are still significant. It’s exciting to get so much information about sensory abilities – about hearing, smell, balance, etc. – British dinosaurs. Using state-of-the-art technology, we essentially got all the brain-related information we could possibly find from these fossils,” Dr Naish said.
In recent years, the EvoPalaeo laboratory at the University of Southampton has carried out substantial research on new spinosaurs from the Isle of Wight. Ceratosuchops itself was not announced by the team until 2021, and its discovery was followed by the publication of another new spinosaur – the gigantic White Rock Spinosaurus – in 2022. Ceratosuchops was scanned at the ?-Vis X-ray Imaging Center at the University of Southampton, home to some of the most powerful CT scanners in the country, and a model of his brain will be on display alongside his bones at the Dinosaur Isle Museum of Sandown, Isle of Wight.
“This new research is just the latest in what amounts to a revolution in paleontology thanks to advances in CT imaging of fossils,” said co-author Lawrence M. Witmer, professor of anatomy at Ohio. University Heritage College of Osteopathic Medicine, which has scanned dinosaurs with CT scans – including Baryonyx — for more than 25 years. “We are now able to assess the cognitive and sensory abilities of extinct animals and explore how the brain evolved in highly behaving dinosaurs like spinosaurs. »
“This new study highlights the important role that UK fossils play in our rapidly changing and evolving understanding of dinosaurs, and shows how the UK – and the University of Southampton in particular – is at the forefront of research. on spinosaurs,” said Dr. Neil Gostling who directs the EvoPalaeoLab at the University of Southampton. “Spinosaurs themselves are one of the most controversial groups of dinosaurs, and this study is a valuable addition to ongoing discussions about their biology and evolution. »