Oldest Fossil Brain Discovered (broadcast Friday, March 6th, 2009)

This video shows a 3-D reconstruction of the braincase in ventral view. Green is the braincase; red shows the endocranial cavity; and orange is the brain. (Credits: Courtesy of Alan Pradel) See More Videos

Scientists have found a 300 million year old fossil shark ancestor with an unusual feature -- fossilized brain tissue within the creature's skull. Writing in the Proceedings of the National Academy of Sciences, the researchers describe the discovery, and the subsequent 3-D imaging used to see inside the skull of the fossil fish known as Sibyrhynchus denisoni.

The fossil was discovered in present-day Kansas. CAT scan and X-ray synchrotron microtomography were used initially to examine the fossil skull, revealing a dense, symmetrical object inside -- the brain. Further work at the European Synchrotron Radiation Facility in France was able to show features as detailed as the optic nerve. We'll talk about the project and what it tells researchers about the evolution of the brain.