Scyphozoa: Systematics
The Scyphozoa is currently divided into the following four orders:
Order Stauromedusae — These are sessile cup-shaped forms, and lack a free-swimming medusa.
Order Coronatae — Most of these are deep-dwelling jellyfish, and are thus rarely seen.
Order Semaeostomae — The so-called disc jellyfish, including the most common as well as the largest of the jellyfish.
Order Rhizostomae — These jellyfish lack tentacles, and have eight oral arms instead of four. The oral arms, often highly branched, have become fused in the center, closing off the central mouth and giving the jellyfish multiple mouth openings at the ends of the lateral arms.
The Cubozoa, or box jellies, were at one time included as an order of the Scyphozoa, but are now considered to be the sister group of the jellyfish.
