When we hear about dinosaur fossils we always think about mineralized remnants of bones but these two are not always one and the same. Sometimes scientists find an impression of a footprint or the trace outlines of an arm or a feathered “wing”.
Then other times, paleontologists hit the motherlode and find dinosaur tissue, with skin and capillaries which represent an amazing discovery. In rare cases, such as the one documented in a special publication by the Geological Society of London, scientists can even find a brain.
It was almost a decade ago when a fossil hunter, exploring the Sussex area in southeastern England, found a small brown pebble. He didn’t put much thought in it but as it turns out, an analysis revealed it to be a fossilized soft brain tissue of an Iguanodon, and herbivores dinosaur which lived at the start of the Cretaceous or some 133 million years ago.
An artist’s impression of a species of Iguanodon.
What’s so special about this discovery is that it’s a first ever discovery of fossilized brain tissue from a dinosaur. The tissue itself no longer exists, but the researchers were able to preserve in immaculate condition all the complex details of its structure.
They performed CT scans on the tissue, which revealed that the fossilized remnants of strands of blood vessels, collagen networks, capillaries and even the outer layers of neural tissues were also perfectly preserved by the natural pickling process.
According to the co-author, Dr. Alex Liu, a paleobiologist at the University of Cambridge, brain tissues “are amongst the least likely issues we would expect to ever be found in a fossilized terrestrial vertebrate.”
They were even able to determine how the unfortunate dinosaur died; near a swamp full of highly acidic, oxygen depleted substances. Tumbling in it, the dinosaur’s brain was, for lack of a better term, “pickled” by the plethora of bacteria in the swamp, which mineralized the brain’s soft tissue before it decayed, keeping it in mint condition.
Appearing some 20 million years after the tame, quadrupedal Stegosaurus and the bird-like Archaeopteryx, Iguanodons were clumsy, chunky, bipedal beasts that mostly ate low-lying vegetation and deterred predators with their strange, thumb spikes. The Iguanodon belonged to the Ornithischians, a group of dinosaurs which didn’t have the true ancestral forms of birds, but according to Liu, its sausage-shaped brain was very similar to a bird and even has some common denominators with the brain of a modern-day crocodile.
It’s known that today’s reptiles have significantly smaller brains which only take up half of their cranial cavity, the other half being filled with sinuses (they serve as a blood drainage system). However, what surprised the researchers is that it seems the Iguanodon brain tissue was pressed tight against the skull, leading them to believe that the dinosaur’s brain was much larger than previously assumed.
“It seems that the brain in this dinosaur was, therefore, more similar to that of modern birds, in that it filled a greater proportion of the braincase,” Liu added.
Still, there’s a possibility that the dinosaur’s unfortunate death caused the brain to be dislodged and, become pressed against the skull and be preserved in that position. They won’t be able to determine the actual size of the brain without seeing its lobes.
Professor Martin Brasier of the University of Oxford who was the lead author of the study, died in a car crash in 2014 while he was still researching and examining this amazing fossil, which is why this special publication is dedicated to his life’s remarkable work.
“Professor Brasier was a very supportive colleague, and it’s been a privilege to work towards publishing a paper on this very special object, in a book in his memory,” said co-author Dr. Russell Garwood, a paleontologist at the University of Manchester.
We’re sure he would have been delighted to be part of such a revelatory finding since there isn’t a better way to determine a dinosaur’s intelligence than by examining its brain.