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133-Million-Year-Old Pebble Discovered to Be First Fossilized Dinosaur Brain

Found on a beach in England, the small fossil contains blood vessel, cortex and part of the membrane that surrounds the brain

(Jamie Hiscocks)
smithsonian.com

Jamie Hiscocks is a veteran fossil hunter. So spotting a small unusual pebble on the beach one night in Bexhill of Sussex County, England, gave him pause. “I could see in my torchlight structured detail on the surface of the object,” he tells Brian Resnick at Vox. “Immediately I knew this wasn't any ordinary pebble.”

In fact, it wasn’t a pebble at all. When he showed the lump of rock to a paleobiologist at Oxford University he eventually identified it as a bit of fossilized dinosaur brain, the first fossil of its kind ever discovered.

Nicholas St. Fleur at The New York Times reports that a team of British and Australian researchers conducted a forensic investigation of the fossil, using a scanning electron microscope to get a closer look. They found blood vessels and capillaries, tissue from the cortex, and even evidence of what they believe is the meninges—the protective layer that attaches the brain to the skull.

Despite unearthing thousands of dinosaurs over two centuries, researchers have never before encountered a dinosaur brain. Resnick points out that soft tissue in animals breaks down rapidly after they die. Only a tiny fraction of animals are preserved after death in just the right conditions to turn their bodies into fossils.

“The chances of preserving brain tissue are incredibly small, so the discovery of this specimen is astonishing,” Alex Liu of Cambridge's Department of Earth Sciences, who co-authored the study on the brain fragment that was recently documented in a special publication of the Geological Society of London, says in a press release.

So how did this tiny bit of brain happen to fossilize? Liu tells Resnick that the dinosaur likely died in or near a body of water, falling in head first. Its skull upside down, gravity caused its brain to press against the top of the cranium. This limited the amount of oxygen that could reach the few millimeters of brain tissue pressing against the skull, preventing decomposition.

As other parts of the brain decomposed, it released iron, phosphate and other enzymes pickling various portions, and within several days a combination of chemicals began mineralizing the few millimeters of brain that were smushed against the skull. That mineralization led to the formation of the fossil.

Eventually, that fossilized brain matter separated and journeyed unknown miles over 133 million years to a tidepool in England. It was pure luck that a winter storm uncovered a bit of beach normally submerged, allowing Hiscocks to discover the strange brain-pebble.

St. Fleur reports that the brain is believed to come from a large herbivorous dino, like an iguanadon. The fragment itself does not reveal much new information about dinosaurs, and its small size does not reveal the larger structure of lobes or tell us how large the complete brain may have been.

Paleontologist David Norman, co-author of the study, tells St. Fleur the main significance of the fossil is its mere existence. It shows that there is the possibility that fossilized brain matter can exist, which may lead paleontolgists to look more carefully at future fossil discoveries. 

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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