Trachylina

invertebrate order

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In cnidarian: Evolution
…ancient of cnidarian classes, and Trachylina is thought to be the most primitive extant order of that group. An alternative view is that anthozoans are the stem of the phylum, which evolved from bilateral flatworms and is secondarily simplified. A corollary to this theory is that the polyp is the…
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In cnidarian: Annotated classification
Order Trachylina Medusa dominant; reduced or no polyp stage. Statocysts and special sensory structures (tentaculocysts). Differ from other hydromedusae by having tentacles inserted above umbrellar margin. Oceanic, mostly warmer waters. Suborder Laingiomedusae Medusae with features of both Narcomedusae and Trachymedusae. Polyp unknown.
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