Anthozoans are a class of cnidarians that include only polyp forms, such as in corals and anemones. Class Anthozoa are exclusively marine and may be either colonial or solitary.
Sources:
Bayer, F. M., et al. 1956. Systematic Descriptions, in Moore, R. C., eds., Treatise on Invertebrate Paleontology, Part F, Coelenterata, Volume 1. The University of Kansas and Geological Society of America. F16-F20 pp.