Semi-aquatic dinosaurs that roamed southern England 125 million years ago inherited their ancestors’ brain capacity 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.
Spinosaurs were adapted with long crocodile-like jaws and conical teeth to stalk riverbanks in search of prey, often large fish.
This way of life was a significant change from that of other theropods, such as Allosaurus and Tyrannosaurus.
Now the researchers have scanned the brain shells of the fossils of baryonyx from Surrey and ceratosuchops from the Isle of Wight to better understand the evolution of spinosaur brains and senses – with the results published in the Journal of Anatomy.
A spokesperson for the University of Southampton said: “The brain shells of both specimens are well preserved and the team digitally reconstructed the internal soft tissues that had long since rotted away.
“The researchers found that the olfactory bulbs, which process odors, were not particularly developed and that the ear was probably tuned to low-frequency sounds.
“Those parts of the brain involved in keeping the head stable and the gaze focused on prey may have been less developed than in later, more specialized spinosaurs.”
Chris Barker, a PhD student at Southampton who led the study, said: “Despite their unusual ecology, it seems that the brains and senses of these early spinosaurs share many aspects with other large-bodied theropods – there is no evidence that their semi-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 part-time fishing, and that the spinosaurs only needed to develop their unusual snouts and teeth to specialize for a semi- aquatic existence.
Contributing author Dr. Darren Naish said: “Because the skulls of all spinosaurs are so specialized for catching fish, it is surprising to see such ‘non-specialised’ brains.
“But the results are still significant. It’s exciting to get so much information about sensory abilities – about hearing, smell, balance and so on – from British dinosaurs. Using advanced technology, we basically extracted all the brain-related information we could from these fossils.”