A special publication of the Geological Society of London contains the results of a research into fossil dinosaur brain tissue that probably belonged to a species of the iguanodon group that lived about 133 million years ago. This fossil found more than a decade ago in Sussex by a fossil hunter is the first example of dinosaur fossil brain studied thanks to a research coordinated by Professor Martin Brasier of Oxford University and Dr. David Norman of the University of Cambridge.
Iguanodontians, scientific name Iguanodontia, are a group of ornithischian herbivorous dinosaurs widespread during the Mesozoic era. Iguanodon is the most famous species in this group because the first fossils were discovered nearly two centuries ago, but between the Jurassic and the Cretaceous period they spread in various continents and diversified into various shapes and sizes.
The discovery of fossilized soft tissues, especially brain tissue, is an extremely rare event. There must be very special conditions to allow these tissues to fossilize and in the case of those of iguanodontians discovered in Sussex they were immersed shortly after the dinosaur’s death into water that had high acidity and a low oxygen content. That delayed the decomposition processes allowing the mineralization that determined fossilization.
This extraordinary fossil was examined using modern techniques: with electron microscope and by subjecting it to a CT scan. These tests allowed to identify the meninges and there are structures that may be cerebral cortex tissue interconnected with capillaries. The brain structure and especially that of the meninges show similarities with those of dinosaurs’ closest living relatives: birds and crocodiles.
One concern is about the possibility that the iguanodontians’s brain pressed directly against the skull while in reptiles generally it only occupies half the space of the cranial cavity. However, it’s possible that this fossil brain started pressing against the skull after the specimen’s death and therefore wasn’t its natural state. The tissues that were preserved are only a part of the brain so it’s not possible to draw definitive conclusions about the iguanodontians’s mental skills.
This study was started several years ago, unfortunately for a certain period was interrupted by Professor Martin Brasier’s sudden death in a car accident in December 2014. The special publication that describes the study is a tribute to him but is also the history of a really unique fossil!
