Ceratium
Dinoflagellata is a phylum of protist algae that have existed from the Triassic into today. Most are salt water plankton but a few live in freshwater. Dinoflagellates either photosynthesize or are mixotrophic, which means they photosynthesize while digesting food. They are a very large group of eukaryotes and live in a wide variety of conditions. Some dinoflagellates play an important role in coral reef ecosystems, some prey on smaller protozoans, and some are parasitic.