It’s looks pretty unassuming, but the small brown pebble-like fossil is actually the brain tissue of a dinosaur that possibly lived 133 million years ago.

It was found almost a decade ago in southern England by fossil hunter Jamie Hiscocks near Bexhill in Sussex and is the only known example of brain tissue from a dinosaur. The tiny specimen was essentially ‘pickled’ when the dinosaur died which explains why it’s managed to stay preserved – soft tissue is extremely rare because it disintegrates so quickly.

“What we think happened is that this particular dinosaur died in or near a body of water, and its head ended up partially buried in the sediment at the bottom,” co-author David Norman, from the University of Cambridge, stated. “Since the water had little oxygen and was very acidic, the soft tissues of the brain were likely preserved and cast before the rest of its body was buried in the sediment.”

David Norman and his team used a scanning electron microscope (SEM) to find collagen and blood vessels along with brain tissue and what looked like parts of the brain cortex. Up until now, little has been known about the structure of a dinosaur’s brain but the sample looked very similar to that of a modern day crocodile and birds.

But the researcher’s say the science world shouldn’t be quick to assume anything from this rare find. They say the example could indicate certain behaviors in the Iguanodon, a large herbivorous dinosaur to which the brain most likely belonged to.

“As we can’t see the lobes of the brain itself, we can’t say for sure how big this dinosaur’s brain was,” he said. “Of course, it’s entirely possible that dinosaurs had bigger brains than we give them credit for, but we can’t tell from this specimen alone.”

Details of the find were announced at the Society of Vertebrate Paleontology’s annual meeting on October 27.