The brain is thought to have belonged to a species closely related to the Iguanodon, a large plant-eating dinosaur that lived during the Early Cretaceous period, about 133 million years ago, and has many features in common with the brains of modern day crocodiles and birds.
Finding fossilised soft tissue, especially brain tissue, is very rare due to the conditions required to create it. The researchers say this piece is so well preserved as it was ‘pickled’ in an acidic, oxygen-deprived body of water shortly after its death, causing the soft tissue to become mineralised.
“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,” said researcher David Norman. “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.”
The team used a scanning electron microscope to identify strands of collagen, blood vessels and meninges (tough membranes that surround the brain) in the specimen. They also found networks of delicate capillaries that may belong to the brain cortex.
“As we can’t see the lobes of the brain itself, we can’t say for sure how big this dinosaur’s brain was,” said Norman. “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. 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.”