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Onchnesoma is one of the two genera that constitute the family Phascolionidae of Phylum Sipuncula, described by Koren and Danielssen established in 1873 as the type species to Onchnesoma steenstrupii.

Description

The species of this genus are usually small in size (with a trunk of less than 1 cm in length). The introverted is much longer than the trunk. The body wall muscle layers presents continuous. The disc may present oral tentacles (usually less than 10 and about 8 mm. in length) arranged around the mouth, but those tentacles can be reduced in size or completely absent. The retractor muscle system is a highly modified introverted form fused to form a muscle retractor. The anus is located in the distal half of introverted. Gallbladder contractile is rarely observed and if present is without villi. They have a single nephridium.

Species

• Onchnesoma intermedium Murina, 1976
• Onchnesoma magnibathum Cutler, 1969
• Onchnesoma squamatum (Koren y Danielssen, 1875)
• Onchnesoma steenstrupii Koren y Danielssen, 1875

References

1. Stephen, A. C., and. Edmonds S. J. (1972): The Phyla Sipuncula and Echiura. vii+528 Trustees of The British Museum of Natural History. London. ISBN 0-565-00717-3
2. Ditadi, A.S.F. & Migotto, A.E. (1982): O Filo Sipuncula. Concelho Nacional de Desemvolvimento Cientifico e Tecnologico CNPq Brasilia. 43p.
3. ^ Cutler, Edward B. & Cutler, Norma J (1985): A revision of the genera Phascolion Théel and Onchnesoma Koren and Danielssen (Sipuncula). Proceedings of Biological Society of Washington 94(4):809-850
4. Cutler, Edward B. & Gibbs, Peter E. (1985): A Phylogenetic analysis of higher taxa in the Phylum Sipuncula. Systematic Zoology 34(2):162-173.
5. ^ Cutler, Edward B. (1994): The Sipuncula: their systematic, biology and evolution. Comstock Publishing Associates of Cornell University. Ithaca, New York. 406p ISBN 0-8014-2843-2 Google Books
6. Cutler, Edward B. (1973): Sipuncula of the Western North Atlantic. Bulletin of American Museum of Natural History, 152(3):103-203.
7. Gibbs, Peter E and Cutler, Edward B. (1987): A classification of the phylum Sipuncula. Bulletin of the British Museum (Natural History) Zoology, 52(1):43-58
8. Murina, V.V. (1976): New and rare species of sipunculida from the East China Sea. Vestnik Zoologi, 2:62-67
9. Cutler, Edward B. (1969): New species of Sipuncula from western North Atlantic. Proceedings of Biological Society of Washington, 82:209-218.
10. Smithsonian National Museum of Natural History. Antarctic Invertebrates: Onchnesoma magnibathum Cutler, 1969 http://invertebrates.si.edu/antiz/taxon_view.cfm?ScreenWidth=1003&ScreenHeight=567&taxon=8585&MODE=taxon
11. ^ Koren, J. and Danielssen, D.C. (1875): Bidrag de norskr Gephyreens Naturhistorie. Nytt. Magasin for Naturvidenskapene, 21:201-138.

External links

• World Register of Marine Species (WoRMS) Onchnesoma Koren & Danielssen, 1876 AphiaID: 136024
• Integrated Taxonomic Information System (ITIS): Onchnesoma Koren and Danielssen, 1875 Taxonomic Serial No.: 154722

• Sipunculans