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The Classes of Coelenterata

Coelenterata is an antiquated name prescribed to the phylum cnidaria. The cnidaria phylum constitutes a group of aquatic organisms such as jellyfish and sea pens. Though they possess well-developed sensory and nervous systems, cnidarians represent the simplest organisms to have achieved tissue organization. The simple ocean creatures of the phylum cnidaria belong to four distinct classes, hydrozoa, scyphozoa, anthozoa and cubomedusae, although some taxonomical controversy surrounds the status of the last class.

Class Hydrozoa
- Hydrozoa class organisms resemble jellyfish and often exhibit colonial behavior, meaning they live together in large groups. The Portuguese man-of-war is the most well-known organism of this class. These hydrozoans live throughout the world's equatorial oceans and sport tentacles as long as 165 feet. Man-of-war tentacles possess venom that causes excruciatingly painful wounds upon contact with human skin. Propita, another hyrodozoan, lives in large colonies that move in unison and form what seems to be one large organism.
Class Scyphozoa
- The scyphozoa class contains most of the jellyfish that commonly come into contact with humans. As with other organisms belonging to the phylum, members of this class possess venom in their tentacles to paralyze prey. Approximately 175 species throughout the world belong to the scyphozoa class. Four major orders of scyphozoans exist, stauromedusae, coronatae, semaeostomeae and rhizostomeae. Species of the aurelia genus, or common jellyfish, belong to this class of organisms.
Class Anthozoa
- Organisms of the class anthozoa differ significantly from all other cnidarians and, according to the University of California Museum of Paleontology, represent the most famous of all cnidarians. Anthozoans run a large gamut and include such organisms as sea anemones, sea fans and sea pens and the coral that builds reefs in tropical regions of the world. The first coral appeared during the Cambrian period, tens of millions of years ago, though the oldest fossilized anthozoans appear older than 550 million years. These living organisms have existed since the days of the dinosaurs.
Class Cubomedusae
- Some controversy surrounds the cubomedusae class of the coelenterata phylum. Bellarmine University considers the cubomedusae a class of the phylum. The Integrated Taxonomic Information System, however, considers it an antiquated, invalid scientific name for the carybdeida, an order belonging to the medusozoa subphylum. Very few species belong to this class, and little information exists on these organisms. They are jellyfish, like those of the scyphozoa and pose no obvious difference to the naked eye of the common observer.

Animals & Science