Stauromedusae are the stalked jellyfishes. They are the sole living members of the class Staurozoa and belong to the Medusozoa subphylum of Cnidaria. They are unique among medusa jellyfish in that they do not have an alternation of polyp and medusa life cycle phases, but are instead interpreted as an attached medusa stage, with a lifestyle more resembling that of polypoid forms. They have a generally trumpet-shaped body, oriented upside-down in comparison with other jellyfish, with the tentacles projecting upwards, and the stalk located in the centre of the umbrella. Stauromedusae usually has eight marginal arms at the top of the calyx. They reach their adult sizes within several weeks, typically 1 to 4 centimeters in length.