Semaeostomeae (literally "flag mouths") is an order of large
jellyfish
Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...
characterized by four long, frilly
oral arms flanking their quadrate mouths. The umbrella is domed with scalloped margins, and the gastrovascular system consists of four unbranched pouches radiating outwards from the central stomach; no ring canal is present. They usually possess eight tentacles; four are per-radical and four are inter-radical.
Taxonomy
The order consists of five families.
* Family
Cyaneidae
* Family
Drymonematidae[Bayha, K. M., and M. N. Dawson (2010). ''New family of allomorphic jellyfishes, Drymonematidae (Scyphozoa, Discomedusae), emphasizes evolution in the functional morphology and trophic ecology of gelatinous zooplankton.'' ]The Biological Bulletin
''The Biological Bulletin'' is a peer-reviewed scientific journal covering the field of biology. The journal was established in 1897 as the ''Zoological Bulletin'' by Charles Otis Whitman and William Morton Wheeler. In 1899 the title was changed to ...
219(3): 249–267
* Family
Pelagiidae
The Pelagiidae are a family of jellyfish. Members of the family ''Pelagiidae'' have no ring canal, and the marginal tentacles arise from umbrella margin.
Genera
There are four genera currently recognized:
*Genus ''Chrysaora'' – (14 species)
*G ...
* Family
Phacellophoridae
''Phacellophora camtschatica'', commonly known as the fried egg jellyfish or egg-yolk jellyfish, is a very large jellyfish in the family Phacellophoridae. This species can be easily identified by the yellow coloration in the center of its body w ...
* Family
Ulmaridae
The Ulmaridae are a family of jellyfish.
Genera
Formerly, the genus ''Phacellophora'' was also included in this family, but is now placed in the family Phacellophoridae.Straehler-Pohl, I., C. L. Widmer, and A. C. Morandini (2011). ''Characteriz ...
Differentiation
The three traditional families, Pelagiidae, Cyaneidae, and Ulmaridae, are distinguishable by these characteristics:
* Gastrovascular cavity divided by radial septa into rhopalar and tentacular pouches
**Pouches simple and unbranched – Pelagiidae
**Pouches branched – Cyaneidae
*Gastrovascular system in form of unbranched and branching canals, or with anastomosing radial canals – Ulmaridae
In addition, members of the Pelagiidae have no ring canal, and the marginal tentacles arise from umbrella margin. Three genera are in this family.
Gallery
Image:Haeckel Discomedusae 18.jpg
Image:Haeckel Discomedusae 28.jpg
Image:Haeckel Discomedusae 8.jpg, "Discomedusae" plate from Ernst Haeckel
Ernst Heinrich Philipp August Haeckel (; 16 February 1834 – 9 August 1919) was a German zoologist, naturalist, eugenicist, philosopher, physician, professor, marine biologist and artist. He discovered, described and named thousands of new s ...
's ''Kunstformen der Natur
(known in English as ''Art Forms in Nature'') is a book of lithographic and halftone prints by German biologist Ernst Haeckel.
...
'', 1904
References
*Collins, A. G.; Jarms, G.; Morandini, A. C. (2022). "Semaeostomeae"
''World Register of Marine Species'' Retrieved 1 November 2022.
*Ruppert, Edward E.; and Fox, Richard S. (1988). ''Seashore Animals of the Southeast'', University of South Carolina Press, 273. .
*Hayward, Peter J.; and Ryland, John S. (1995). ''Handbook of the Marine Fauna of North-West Europe'', Oxford University Press, 65. .
*Bayha K., Dawson M. (2010) New family of allomorphic jellyfishes, Drymonematidae (Scyphozoa, Discomedusae), emphasizes evolution in the functional morphology and trophic ecology of gelatinous zooplankton. Biological Bulletin 219: 249–267.
Discomedusae
Cnidarian orders
{{Scyphozoa-stub