The semi-aquatic dinosaurs that roamed southern England 125 million years ago inherited the brain capacity from their ancestors to catch the fish they survived on, according to new research.
Scientists from the University of Southampton and Ohio University have reconstructed the brains and inner ears of two spinosaurs, which they say helps reveal how these large predatory dinosaurs interacted with their environment.
Spinosaurs were adapted with long crocodile-like jaws and conical teeth to occupy riverbanks in search of prey, often large fish.
This lifestyle was a major change from that of other theropods, such as Allosaurus and Tyrannosaurus
The researchers scanned the braincases of baryonychus fossils from Surrey and ceratosuchops from the Isle of Wight during the study.
The aim was to better understand the evolution of the spinosaurus brain and senses – with the results published in the Journal of Anatomy.
Chris Barker, a PhD at Southampton who led the study, said: “Despite their unusual ecology, it appears that the brain and senses of these early spinosaurs retained many aspects in common with other large theropods – there is no evidence that their half “Aquatic lifestyles are reflected in the way their brains are organized.”
He explained that one interpretation of this evidence was that the theropod ancestors of spinosaurs already possessed brains and sensory adaptations suitable for partially catching fish.
This, he suggests, means that spinosaurs only needed to evolve their unusual snout and teeth to become specialized for a semi-aquatic existence.
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Contributing author Dr Darren Naish said: “Because the skulls of all spinosaurs are so specialized for catching fish, it is surprising to see such ‘unspecialised’ brains.
“But the results are still important. It’s exciting to get so much information about sensory abilities – about hearing, smell, balance and so on – from British dinosaurs.
“Using cutting-edge technology, we basically got all the brain-related information we possibly could from these fossils.”
A University of Southampton spokesman said: “The braincases of both specimens are well preserved and the team digitally reconstructed the internal soft tissues that had long since decayed.
“The researchers found that the olfactory bulbs, which process smells, were not highly developed and the ear was probably tuned to low-frequency sounds.
“Those parts of the brain involved in keeping the head steady and looking at prey were probably less developed than in later, more specialized spinosaurs.”