Andreolepis Fossil (IMAGE) Uppsala University Caption In a paper published in Nature, a team of researchers from Uppsala University and the ESRF in France apply synchrotron x-ray tomography to a tiny jawbone of a 424 million year old fossil fish in order to illuminate the origin of this strange system of tooth replacement. Credit Henning Blom Usage Restrictions May only be published in connection to reports about the research by Chen et al. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.