Semaeostomeae

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Semaeostomeae

Semaeostomeae is an order of large jellyfish in the group Discomedusae (within the class Scyphozoa). They are easy to recognize by four long oral arms around their four-sided mouths and a domed bell with wavy edges.

What they look like and how they live
- The bell (umbrella) is dome-shaped with scalloped margins.
- They have four main gut pouches radiating from the center and no ring canal.
- Most species have eight tentacles: four near the edges and four between them.
- An example group you might know is the sea nettles, such as Chrysaora fuscescens.

Classification and families
- Semaeostomeae includes five families: Cyaneidae, Drymonematidae, Pelagiidae, Phacellophoridae, Ulmaridae.

Key differences among the main groups
- Pelagiidae
- Gut cavity is divided into simple, unbranched pouches.
- No ring canal.
- Marginal tentacles arise from the edge of the bell.
- About three genera in this family.
- Cyaneidae
- Gut pouches are branched.
- Ulmaridae
- Gut canal system can be simple, branched, or a network (anastomosing radial canals).

Taxonomic placement (simplified)
- Kingdom: Animalia
- Phylum: Cnidaria
- Class: Scyphozoa
- Subclass: Discomedusae
- Order: Semaeostomeae

Note: This is a concise overview of the main features and classification.