In 2004, Jamie Hiscock of East Sussex, England, and his brother, both fossil enthusiasts, found fossilised bits of Iguanodon, a roughly 30-foot dinosaur that roamed the earth around 130 million years ago.
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 palaeontologist at the University of Durham in the UK unaffiliated with the paper.
The research team concluded that the sample was basically pickled. 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 fossilisation 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 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.