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Researchers reveal evolution of oldest Spinosaur brains

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


Lawrence M. Witmer, professor of anatomy at OHIO’s Heritage College of Osteopathic Medicine, and Ryan Ridgley, a research associate of 23 years in WitmerLab, specifically focused their research efforts and contributed information on Baryonyx, one of the species of spinosaurs highlighted in the study.

俄亥俄州传统骨科医学院(Heritage College of Osteopathic Medicine)的解剖学教授劳伦斯·M·维特默(Lawrence M. Witmer)和在维特默实验室(WitmerLab)工作了23年的助理研究员瑞安·里奇利(Ryan Ridgley),特别专注于他们的研究工作,并提供了有关重石龙(Baryonyx)的信息,重石龙是研究中重点关注的棘龙物种之一。

The most famous spinosaur is Spinosaurus itself, a 45-foot-long, sail-backed giant that was one of the stars of Jurassic Park III. 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 riverbanks in quest of prey, among which were large fish. This way of life was very different from that of more familiar theropods, like 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 huge creatures lived long before Spinosaurus and would have been roaming the planet about 125 million years ago. The braincases of both specimens are well preserved, and the team digitally reconstructed the internal soft tissues that had long rotted away.


The researchers found the olfactory bulbs, which process smells, weren’t particularly developed, and the ear was probably attuned to low frequency sounds. Those parts of the brain involved in keeping the head stable and the gaze fixed on prey were possibly less developed than they were in later, more specialized spinosaurs.


Findings were recently published in a freely accessible article in the Journal of Anatomy.


“Despite their unusual ecology, it seems the brains and senses of these early spinosaurs retained many aspects in common with other large-bodied theropods—there is no evidence that their semi-aquatic lifestyles are reflected in the way their brains are organized,” said University of Southampton Ph.D. student Chris Barker, who led the study.


One interpretation of this evidence is that the theropod ancestors of spinosaurs already possessed brains and sensory adaptations suited for part-time fish catching, and that ‘all’ spinosaurs needed to do to become specialized for a semi-aquatic existence was evolve an unusual snout and teeth.


Ohio University researchers help reveal evolution of oldest spinosaur brains
Three-dimensional reconstruction of the brain endocast (purple), cranial nerves (yellow), inner ear (pink) and blood vessels (red and blue) of the British spinosaurid Ceratosuchops inferodios (bottom) and Baryonyx walkeri (top). Credit: Chris Barker


“Because the skulls of all spinosaurs are so specialized for fish-catching, it’s surprising to see such ‘nonspecialized’ brains,” said contributing author Dr. Darren Naish. “But the results are still significant. It’s exciting to get so much information on sensory abilities—on hearing, sense of smell, balance and so on—from British dinosaurs. Using cutting-edged technology, we basically obtained all the brain-related information we possibly could from these fossils,” Dr. Naish said.