|The brain endocast and a tomographic rendering of it. Scale bar is one centimetre|
Endocasts form when sediment infills a skull and preserves an internal mould of the brain case. These are typically simple objects which record topography. This specimen, however, is one of those rare examples where the internal microstructure of the brain is also preserved.
133 million years ago Sussex was a swampy floodplain environment interspersed with forests. Anoxic, acidic conditions in the swamps prevented bacterial decay while fine sediment allowed for faithful preservation of the microstructure. In this case this is the first instance it has been recorded from a dinosaur.
The chances of preserving brain tissue are incredibly small, so the discovery of this specimen is astonishing," said co-author Dr Alex Liu from Cambridge's Department of Earth Sciences.
Using a mix of SEM and CT scanning, an international team of researchers were able to reconstruct networks of blood vessels and collagen strands within the outer neural tissues of the meninges. The shape of the endocast showed that it likely came from a close relative of Iguanodon, one of the first dinosaurs to be named. The structure of these meninges was neurologically closest to crocodiles and birds. This makes sense as phylogenetically crocodiles are their closest living relatives while birds are nested within the dinosaur clade.
'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.'
The discovery of a dinosaur brain is a crucial step in palaeontology being able to study dinosaur physiology as if these creatures were alive today.