3 Heads (image) University of Leicester Caption This image shows progressive stages of decay of a close relative of vertebrates (amphioxus) approaching ancestral morphology and thus skewing fossil interpretation. Credit University of Leicester Usage Restrictions Use only with credit. 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.