Researchers collecting bulk sediment samples (IMAGE) Proceedings of the National Academy of Sciences Caption Researchers collecting bulk sediment samples from a Holocene reef in the Dominican Republic, continuing the search for dermal denticles in other regions. Credit Image credit: Sean Mattson (International Center for Tropical Agriculture, Cali, Colombia). Usage Restrictions None 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.