Comb Jellies (IMAGE) Penn State Caption Various species of comb jellies, the most ancient group of animals with a nervous system alive today, are shown. Credit David Simmons, University of Florida Usage Restrictions The image credit must be published along with the image. 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.