After years of studying what appeared to be a small mud-colored stone, paleontologists announced they had found fossilized dinosaur brain tissue.

The small specimen, estimated to be around 133 million years old, was found in Bexhill, England and is suspected to have belonged to an herbivore similar to Iguanodon, one of the first dinosaurs ever studied in the early 1800s.

Paleontologists had previously found braincases, but the preserved tissue will give researchers insight into how soft tissue is preserved, according to David Norman, a paleontologist at the University of Cambridge.

Norman and others believe the unlucky dinosaur sank into a stagnant pond after death, turning belly up, leaving the head upside down and buried in the lakebed.

“This might encourage people to look for evidence of soft tissues in land-living fossil animals, something that is normally a field in which aquatic organisms tend to preserve soft tissues.”

The preservation process replaced the soft tissues with calcium phosphate and iron carbonate. The minerals replicated the original tissues, which can last millions of years.

“In this instance it seems likely that stagnant—low oxygen—acidic water acted as the hardening agent,” Norman said. “The acid water literally preserved and hardened the soft tissues, similar to the preservation of things like soft fruits by pickling.”

Norman said the discovery was in memory of the late paleobiologist Martin Brasier, and was found nearly 12 years before it was confirmed to be brain tissue. Brasier started work on the specimen, but died suddenly in a vehicle crash in 2014.

“Martin and I were busy with other projects and only met occasionally to argue about how to interpret the fossil,” Norman said. “It was not top of our own list of projects to be completed, and we were happy to argue and debate—as good scientists often do. It was only much later that we came to an agreement about how to interpret the fossil and turn this into a scientific paper. It has been slightly surprising to see all this interest in our little bit of science.”

Bexhill, a seaside town, lies close to the fossiliferous Jurassic Coast. The specimen and was so well preserved Norman and his colleagues could compare the fossil to the skull structures of modern dinosaurs: birds and crocodiles.

“The structures we see are pretty much as we might have expected by inference from comparative anatomy,” Norman said. “So, all we are doing is showing that a dinosaur had brain tissues inside its braincase.”

Due to its well-preserved state, the team saw the tissue was directly against the braincase, which could mean the dinosaur’s brain filled the entire cavity. The finding could imply the dinosaur and other herbivores were smarter than originally thought.

But the team’s final report cautioned looking too far ahead, and noted the tissue could have ended up compacted against the skull when the dinosaur fell into the bog.

The team may consider using high resolution synchrotron imaging to see if  any discoveries could be made to learn more about the structure of the brain membranes. The fossil is currently in a private collection, a challenge to any further research.

Dr. David Norman is a dinosaur anatomist and zoologist. He helped identify the specimen and interpret the mineralized soft tissues, and explained its preservation. He is currently working on a detailed description of a dinosaur skeleton found in Lyme Regis in Dorset, in the southwest of England. A second edition of his book, A Very Short Introduction: Dinosaurs, will be released in early 2017 through Oxford University Press.