Researchers may have found something extraordinary inside a plain-looking pebble: fossilized dinosaur brain. They described their findings [PDF] in a special publication from the Geological Society of London. 

Twelve years ago, fossil hunter and paper co-author Jamie Hiscocks was looking through an exposed sandstone riverbed in Sussex, England, when he spotted a round brown stone. Hiscocks brought the rock to the attention of renowned paleobiologist Martin Brasier at the University of Cambridge. The two men immediately began speculating on the rock’s contents.

“I noticed there was something odd about the preservation,” Hiscocks said in a statement, “and soft tissue preservation did go through my mind. Martin realized its potential significance right at the beginning.”

Brasier and colleagues at the University of Cambridge and the University of Western Australia began exploring the mysterious rock from every imaginable angle. They put it through a computed tomography (CT) scanner to look inside and examined its smallest details using super-high-powered microscopes.

What they found astounded them. The nondescript-looking rock, they say, concealed the remains of some prehistoric animal’s brain. Close-up images revealed fragments from the supportive membrane surrounding the brain, plus blood vessels and cortices from within.

The arrows point to blood vessels in the meninges, or supportive membrane. Image Credit: David Norman

The team believes the brain may have belonged to an iguanodon-like dinosaur that lived in the Early Cretaceous period around 133 million years ago. The fact that the chunk of brain has lasted this long is “astonishing,” said co-author Alex Liu.

The researchers say the brain’s owner likely met its demise in or near a body of water. It probably then became at least partially submerged and buried in sediment at the bottom, where acidic water and a lack of oxygen helped preserve the tissue.

"As we can't see the lobes of the brain itself, we can't say for sure how big this dinosaur's brain was," co-author David 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."

However, some paleontologists are reserving judgment about the fossil until further research is done, including the American Museum of Natural History's Mark Norell, who told NPR he is "not convinced" the find is a dinosaur brain.

Martin Brasier did not live to see the results of this research, but the team's report on their findings was published in a special volume dedicated to his life and work.
 
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