Jellyfish always much greater than the Lion's Mane, whose bell diameter can reach . The rarely encountered deep-sea jellyfish "Stygiomedusa gigantea" is another candidate for "largest jellyfish", with its thick, massive bell up to wide, and four thick, "strap-like" oral arms extending up to in length, very different from the typical fine, threadlike tentacles that rim the umbrella of more-typical-looking jellyfish, including the Lion's Mane. Jellyfish have a complex life cycle which includes both sexual and asexual phases, with the medusa being the sexual stage in most instances. Sperm fertilize eggs, which develop into larval planulae, become polyps, bud into ephyrae
Jellyfish authorities state that neither of these are jellyfish, which they consider should be limited to certain groups within the medusozoa. The non-medusozoan clades called jellyfish by some but not all authorities (both agreeing and disagreeing citations are given in each case) are indicated with "???" on the following cladogram of the animal kingdom: Jellyfish are not a clade, as they include most of the Medusozoa, barring some of the Hydrozoa. The medusozoan groups included by authorities are indicated on the following phylogenetic tree by the presence of citations. Names of included jellyfish, in English where possible, are shown in boldface;