cnidarian, also called coelenterate, any member of the phylum Cnidaria (Coelenterata), a group made up of more than 9,000 living species. Mostly marine animals, the cnidarians include the corals, hydras, jellyfish, Portuguese men-of-war, sea anemones, sea pens, sea whips, and sea fans.

What are the 4 types of cnidarians?

There are four major groups of cnidarians:

• Anthozoa, which includes true corals, anemones, and sea pens;
• Cubozoa, the amazing box jellies with complex eyes and potent toxins;
• Hydrozoa, the most diverse group with siphonophores, hydroids, fire corals, and many medusae; and.
• Scyphozoa, the true jellyfish.