Dinosaur Brain Fossil Revealed for the First Time

A pebble-sized object found in 2004 by a U.K. fossil hunter has just been confirmed as the first known fossilized brain tissue from a dinosaur.

The remarkable discovery, dating to the Cretaceous Period 133 million years ago, offers insight into dinosaur evolution, behavior, intelligence and brain structure.

Scanning electron microscope analysis of the fossil reveals it is a fossilized portion of a brain that belonged to an Iguanodon-like dinosaur. Iguanodon, meaning "Iguana Tooth," was a large, plant-eating dinosaur that lived during the Early Cretaceous. It could grow up to 43 feet long and possibly more, according to some estimates.

David Norman, a University of Cambridge paleontologist, described the fossil's surface as showing "areas of encrusted material that has, under microscopic examination, a curious and highly unusual texture, rather like wrinkled fabric to the naked eye."

Norman said that "wrinkled fabric" is made up of several layers that appear very similar to the meninges — tissue that surround the brain in the brain cavity. The layers of the meninges protect and support the brain's softer tissues.

Animation of the fossilized dinosaur brain tissue (Credit: University of Manchester):

Norman and his team believe that the fossil contains some of the meninges that surrounded the dinosaur's brain, as well as strands of collagen and blood vessels. Structures that could represent tissues from the brain cortex — its outer layer of neural tissue — interwoven with delicate capillaries, also appear to be present.

The brain segment has similarities with the brains of modern-day descendants of dinosaurs, namely birds and crocodiles, strengthening the case that all of these animals are related.

The fossil suggests that the brain was "not a tight fit" in the animal's braincase, Norman said, explaining that, unlike birds, the dinosaur's brain only took up about 50 percent of its braincase's volume.

At first some of the researchers suspected the dinosaur's brain was quite large, since it looks as though the upper brain membranes were pressed against the braincase wall at the top of the animal's skull.

"But, in fact, the only way this specimen could have been preserved was if the head was upside down and the brain has 'flopped' down onto the braincase roof as it started to decay," Norman said.

Co-author Alex Liu of Cambridge's Department of Earth Sciences added, "The chances of preserving brain tissue are incredibly small, so the discovery of this specimen is astonishing."

Iguanodon (left) with the discovered brain fossil and its parts highlighted. "Bc," for example, stands for braincase, while "Gm" refers to gray matter.

The team believes the piece of brain was essentially pickled in a highly acidic and low oxygen body of water shortly after the dinosaur's death. The enormous animal might have keeled over near a bog or swamp. Its cause of death is unknown, but Liu said that "the soft tissues of the brain were likely preserved and cast before the rest of its body was buried in the sediment."

While it's fortunate that where the dinosaur fell allowed part of its brain to be pickled for posterity, Norman points out that the "acidic 'pickling' process would have denatured any of the biological molecules." That means no DNA can now be extracted from the fossil.

Nevertheless, "Any time we get soft tissue preservation in a dinosaur it's cause for celebration since it gives us such a unique window into the biology of these animals," Lawrence Witmer, a professor of anatomy and paleontology at Ohio University who did not work on the research, told Seeker.

Read more at Discovery News