Jamie Hiscock of East Sussex, England has a knack for spotting incredibly preserved remnants of life.
Five years ago, he and his brother, both fossil enthusiasts, were walking along the beach when they noticed a remarkable piece of amber. When scrutinized in a lab, it turned out to hold the world’s oldest spider web. The siblings have also found fossilized bits of Iguanodon, a roughly 30-foot dinosaur that roamed the earth around 130 million years ago.
So when Hiscock picked up a small, brown doodad in Bexhill, Sussex in 2004, he knew it wasn’t any old rock. But he had no idea it’d be the first example of a fossilized dinosaur brain.
“I noticed there was something odd about the preservation,” he said in a statement. “It wasn’t until years later that its true significance came to be realized.”
Hiscock took the sample to Martin Brasier, a paleobiologist at the University of Oxford, with whom he had worked before. On Oct. 27, over a decade later, a team of researchers from the University of Cambridge and the University of Western Australia published their findings that what Hiscock had actually found was the first example of preserved dinosaur brain, likely also an Iguanodon, from about 133 million years ago.
“The preservation of brain tissue in this way is so unbelievably unlikely that it just shouldn’t have happened—yet here it is,” says Martin Smith, a paleontologist at the University of Durham in the UK unaffiliated with the paper.
The research team concluded that the sample was basically pickled. We usually think of pickling in its culinary application, but the basic method used to turn cucumbers into pickles is an act of preservationthat can be applied to any organic matter: adding acid and preventing oxygen exposure creates the perfect environment for certain (safe-to-eat) bacteria to thrive, and these crowd out other bacteria that would ordinarily decompose your cucumber.
In the case of the dino brain, the team concluded that the dinosaur must have died near some kind of swampy, acidic body of water. When the animal died, its head likely worked its way into the sediment at the bottom of the water. While bacteria living in the water began breaking down the rest of the dinosaur, they simultaneously used up all the oxygen present. So the head was left in a sort of Jurassic pickling jar.
Eventually, the soft tissue hardened through the normal fossilization process.
“The level of preservational detail is astounding—with individual blood vessels, each narrower than a human hair, standing proud of the brain surface,” Smith says. This kind of detail, “is only present due to the rapid impregnation of the original tissue by phosphatic minerals, which must have occurred hours to days after the organism’s demise.”
The team examined the brain using a powerful electron microscope that uses a beam of electrons to create an image of the specimen. They provide for much finer detail than standard microscopes, which use light wavelengths—and enabled the scientists to see exactly what this particular brain fossil was made of.
The dino brain appears similar to the brains of modern-day reptiles, but because it wasn’t a complete brain, the researchers can’t say for sure how intelligent this animal may have been.
Soft-tissue fossilization of any kind is extremely rare. Although Hiscock is holding onto the brain for now, he’s in talks to have it placed in a public museum.
This article originally appeared on Quartz.