Brown pebble turns out to be first ever pickled dinosaur brain

The specimen is thought to have come from a large plant eater such as iguanodon, which lived about 133 million years ago.

Scientists believe the dead dinosaur’s head was buried in mud at the bottom of a swamp, allowing its brain to be “pickled” and preserved.

In time the soft tissues became mineralised. But the fossil retained distinctive features such as the meninges – a protective membrane surrounding the brain – blood vessels, collagen and structures thought to represent the outer layer of nerve cells, or cortex.

Lucky find

A detailed study of the “pebble” has revealed similarities with the brains of present-day birds and crocodiles, both close relatives of dinosaurs.

“The chances of preserving brain tissue are incredibly small, so the discovery of this specimen is astonishing,” said Alex Liu, from Cambridge University’s Department of Earth Sciences, who took part in the analysis.

The find’s importance was first recognised by the late Martin Brasier, from Oxford University, who co-led the research prior to his death in a road accident in 2014.

It is highlighted in a Special Publication of the Geological Society of London published in tribute to the professor, who was one of the world’s leading palaeobiologists.

Fossil hunter Jamie Hiscocks, who discovered the specimen on a beach near Bexhill-on-Sea in 2004, and is named as one of the study’s authors, said: “I have always believed I had something special. I noticed there was something odd about the preservation, and soft tissue preservation did go through my mind.”

Pickled in bog

“Martin realised its potential significance right at the beginning, but it wasn’t until years later that its true significance came to be realised,” said Hiscocks.

“In his initial email to me, Martin asked if I’d ever heard of dinosaur brain cells being preserved in the fossil record. I knew exactly what he was getting at. I was amazed to hear this coming from a world-renowned expert like him.”

David Norman, from Cambridge University, who worked with Brasier on the specimen, said the brain tissue had, in effect, been “pickled” in a highly acidic, low oxygen environment – probably a bog, or swamp.

“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,” said Norman.

“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.”

Dinosaur with big brain?

Typically in reptiles, the brain is surrounded by a dense drainage system consisting of blood vessels and vascular chambers. The brain itself only takes up about half the space within the skull cavity.

But, surprisingly, the tissue in the fossilised dinosaur brain appears to have been pressed directly against the skull. This raises the intriguing possibility that some dinosaurs had larger brains than previously thought.

However the scientists cautioned against jumping to too many conclusions about dinosaur intelligence.

The most likely explanation was that as the brain decayed after death gravity caused it to collapse against the roof of the skull cavity, they pointed out.

“As we can’t see the lobes of the brain itself, we can’t say for sure how big this dinosaur’s brain was,” Norman 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.

“What’s truly remarkable is that conditions were just right in order to allow preservation of the brain tissue. Hopefully, this is the first of many such discoveries.”