Hydroidolina
- Anthoathecata
- Archaeolafoea
- Cambrohydra
- Eisenackiella
- Plotocnide borealis
Photo: Aino Hosia/Universitetsmuseet i Bergen, Universitetet i Bergen · CC BY-SA 4.0 This animal has a swimming medusa and a minute mud-dwelling polyp. DNA research connected forms that had been treated as separate species.
