Hey, rockhounds! Keep a sharp eye out for the unusual. An odd-looking brown pebble found on a southeastern English shore turned out to be the first evidence of a dinosaur’s brain!

Thankfully, the dinosaur experts who made this discovery had much larger brains than the DONOR dino—probably a 15- to 20-foot-long Early Cretaceous creature related to the iguanodon depicted here.

Fossil finder Jamie Hiscocks was combing a beach near Bexhill a dozen years ago when the encrusted-looking brown pebble caught his eye. Like any good rockhound, he kept the specimen even though he had no idea what he had found.

Usually, it’s the hard parts of a dinosaur that are fossilized like bones and teeth. Soft tissue like a dino- saur’s skin, muscle or internal organs almost always decayed too quickly for fossilization to occur.

That’s why Oxford University paleontologist Martin Brasier took an interest in this small nd. Under magnification, it looks like fine structures were preserved. So he handed the specimen over to David Norman, a paleobiologist at Cambridge University. Norman was thrilled and recognized it immediately as a cast fossil of some part of a dinosaur’s brain!

This startling discovery was just described in a special edition put out by the Geological Society of London to honor study co-author Brasier, who passed away two years ago.

In the study, the dino experts say that this plant eater likely died upside down 133-million years ago in a swampy area with the top of its head soaking in some highly acidic, low-oxygen water. These strange conditions led to part of its brain being fossilized!

The whole brain was larger, according to the study. The fossil consists of small capillaries, some brain tissue and mostly the tough outer covering of its brain.