Euphausiacea

The Antarctic krill Euphausia superba, from here.

Belongs within: Eumalacostraca.

The Euphausiacea, krill, are reasonably sized (generally some centimetres long) pelagic, shrimp-like crustaceans. They are best known for their role in the marine ecosystem as food for larger animals, due to their habit of forming large swarms.

Characters (from Ax 2000): Carapace fused to first eight thoracomeres, forming cephalothorax (lateral folds of carapace covering only upper parts of gills); telson with long narrow subapical appendages on posterior third.

<==Euphausiacea
    |  i. s.: Meganyctiphanes norvegica BA04, W81
    |         Thysanopoda CH97
    |           |--T. acutifrons B26
    |           |--T. orientalis B26
    |           `--T. tricuspidata CH97
    |         Stylocheiron CH97
    |           |--S. abbreviatum B26
    |           |--S. carinatum B26
    |           `--S. suhmii CH97
    |--Bentheuphausia B26 [Bentheuphausiidae MD01]
    |    `--B. amblyops B26
    `--Euphausiidae MD01
         |--Thysanoessa B70
         |    |--T. gregaria W81
         |    |--T. inermis W81 [=Rhoda inermis B26; incl. T. neglecta B26]
         |    |--T. longicaudata B26
         |    |--T. longipes W81
         |    |--T. parva B26
         |    `--T. raschii B26
         |--Nyctiphanes B70
         |    |--N. australis HR96
         |    `--N. couchii B26
         |--Nematoscelis B70
         |    |--N. atlantica B26
         |    |--N. difficilis B70
         |    |--N. megalops B26
         |    |--N. microps B26
         |    `--N. tenella B26
         |--Tessarabrachion oculatus B70
         `--Euphausia DAS03
              |--E. americana B26
              |--E. brevis B26
              |--E. hemigibba B26
              |--E. krohnii B26
              |--E. lucens W81
              |--E. mutica B26
              |--E. pacifica CH97
              |--E. similis K-M02
              |--E. superba Dana 1852 DAS03
              |--E. tenera B26
              `--E. vallentini W81

*Type species of generic name indicated

REFERENCES

Ax, P. 2000. Multicellular Animals: the phylogenetic system of the Metazoa vol. 2. Springer.

[B26] Bigelow, H. B. 1926. Plankton of the offshore waters of the Gulf of Maine. Bulletin of the Bureau of Fisheries 40 (2): 1-509.

[B70] Briggs, J. C. 1970. A faunal history of the North Atlantic Ocean. Systematic Zoology 19 (1): 19-34.

[BA04] Bucklin, A., & L. D. Allen. 2004. MtDNA sequenceing from zooplankton after long-term preservation in buffered formalin. Molecular Phylogenetics and Evolution 30: 879-882.

[CH97] Castro, P., & M. E. Huber. 1997. Marine Biology, 2nd ed. WCB McGraw-Hill: Boston.

[DAS03] Dixon, C. J., S. T. Ahyong & F. R. Schram. 2003. A new hypothesis of decapod phylogeny. Crustaceana 76: 935-975.

[HR96] Heather, B. D., & H. A. Robertson. 1996. The Field Guide to the Birds of New Zealand. Viking: Auckland.

[K-M02] Klein-MacPhee, G. 2002. Jacks. Family Carangidae. In Bigelow and Schroeder’s Fishes of the Gulf of Maine (B. B. Collette & G. Klein-MacPhee, eds) 3^rd ed. pp. 411-427. Smithsonian Institute Press: Washington.

[MD01] Martin, J. W., & G. E. Davis. 2001. An updated classification of the Recent Crustacea. Natural History Museum Los Angeles County, Science Series 39: 1-124.

[W81] Watson, L. 1981. Sea Guide to Whales of the World. Hutchinson: London.