<i>Ornithocercus thumii</i> (IMAGE) Proceedings of the National Academy of Sciences Caption Ornithocercus thumii, a marine dinoflagellate with cyanobacterial symbionts. Ornithocercus species cells are surrounded by a cellulosic covering and crown-shaped extensions of the covering that form an extracellular chamber. A number of coccoid, brown-colored cyanobacteria reside in the specialized chamber. Credit Takuro Nakayama 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.