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We’ve Finally Found a Dinosaur Brain

A rock picked up on a Sussex beach in 2004 looked a whole lot like part of a reptile brain. In a manner of speaking, it was.
The iguanodon.

The iguanodon.

It may have been little more than a curiosity when fossil hunter Jamie Hiscocks picked up a funny looking rock on a beach in Sussex, England, in 2004. A decade on, it turns out that rock was much more than a mere oddity: It was a piece of fossilized brain tissue, most likely belonging to a dinosaur that lived 133 million years ago.

“This isn’t a revelation. Of course a dinosaur had a brain, but we’re actually seeing some of the textures of the brain themselves, which I never thought we’d ever do,” says University of Cambridge paleobiologist David Norman, a coauthor of the new study, in a video accompanying the announcement.

Norman’s pessimism was not entirely unjustified. Soft tissues such as skin, muscle, and brain often decay before they have a chance to fossilize, leaving little more than skeletons behind. But under the right conditions—most importantly, a low-oxygen environment such as one might encounter within a bog, swamp, or, somewhat more famously, tar pits—soft tissues can survive for thousands or even millions of years.

“We’re actually seeing some of the textures of the brain themselves, which I never thought we’d ever do.”

Whatever it was that preserved this particular specimen, Norman, together with Alexander Liu and other colleagues, took a look at the rock and thought it bore a close resemblance to the outer protective layer, or meninges, of a small reptile brain. A comparison with previously discovered fossils suggests it would fit inside the brain case of an iguanodon or a similar dinosaur. The timing is about right too—the fossil was found near the Tumbridge Wells sand formation, which formed roughly 133 million years ago.

The dinosaur brain.

The dinosaur brain.

Closer inspection using a scanning electron microscope and a technique called X-ray microtomography—essentially, a three-dimensional reconstruction based on a collection of X-ray images—revealed structures resembling the meninges of modern-day birds and reptiles, along with other structures with “considerable fine-scale complexity,” which the researchers speculate could be the fossilized remains of individual neurons in the brain.

The research is reported in a special publication of the Geological Society of London in honor of Martin Brasier, who is credited as first author on the study. Liu’s advisor and a well-regarded Oxford University paleobiologist, Brasier died in a car accident in 2014.