Thursday, 10 November 2016

A Preserved Dinosaur Brain (Yep You Read It Right)

From nervous systems and skin to DNA and proteins, recent advances in technology combined with new discoveries and analyses of old specimens have rapidly broadened the parameters of what we know the fossil record is capable of preserving. Yet sometimes the fossil record throws up specimens which seem like they are straight out a science fiction story. The idea of finding a fossilised dinosaur brain sounds like a plot element from an outlandish B movie, but against all expectations that is exactly what has been uncovered. What is more, this brain is not from an exciting new site in China or Brazil, both famous for the remarkable quality of many of their fossils, but from the UK - the home of dinosaur palaeontology and palaeontology itself.

The brain endocast and a tomographic rendering of it. Scale bar is one centimetre
The specimen was found in 2004 by an amateur fossil hunter near Bexhill, Surrey. To the untrained eye it is just a small brown pebble, but distinctive features show it to be an endocast of a dinosaur skull.

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.