(CN) - While paleontologists will never know what dinosaurs thought about, they might have a better idea of what some of their brains looked like thanks to the first-ever discovery of a dinosaur brain fossil.
A British fossil hunter found what he thought was an ordinary-looking brown pebble on a beach in Essex, England. But after noticing its unusual shape and texture, he decided to bring it to the renowned paleobiologist Martin Brasier.
Brasier, who died in a traffic accident in 2014, worked with David Norman from the University of Cambridge to determine whether the discovery was part of a dinosaur brain and, if so, which species.
After examining the pebble, the researchers established that the fossil was mineralized brain tissue, likely preserved after the dinosaur's head fell in a bog or swamp. The team also estimated that the fossil is 133 million years old and a relative of Iguanodon, an iconic herbivorous dinosaur that lived during the early Cretaceous of 100 to 145 million years ago.
"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," Norman said. "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."
Norman and his colleagues published their findings Thursday in a Special Publication of the Geological Society of London, in tribute to Brasier.
Finding fossilized soft tissue is very rare, especially considering the age of the specimen examined by Norman's team.
"The chances of preserving brain tissue are incredibly small, so the discovery of this specimen is astonishing," said study co-author Alex Liu.
The researchers used scanning electron microscope techniques to identify portions of the specimen that are typically found in brains, such as strands of collagen and blood vessels, as well as tissues from the brain cortex — its outer layer of neural tissue. The structure of the fossilized brain shows similarities to the brains of present-day descendants of dinosaurs, specifically crocodiles and birds.
The fossil is noticeably different from the brain of typical reptiles, however. Reptile brains tend to be the shape of sausages, surrounded by a dense region of blood vessels and thin-walled sinuses that serve as a blood drainage system. In this fossil, the brain appears to have been pressed directly against the skull, which could be a sign that some dinosaurs had large brains that filled much more of the cranial activity, though the researchers say that shouldn't lead to new conclusions about the intelligence of dinosaurs.
"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," Norman said. "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."
Other researchers would like to see more evidence.
Mark Norell of the American Museum of Natural History told NPR that he's concerned with the differences between the team's findings and the modern knowledge of dinosaur brain anatomy that was developed with advanced technology. He was also hesitant to accept the findings since the brain was not in a public repository where other researchers could study the fossil.
"I'm not convinced," he said.
Read the Top 8
Sign up for the Top 8, a roundup of the day's top stories delivered directly to your inbox Monday through Friday.