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.[1][2][3][4][5]

Scientific classification

Koren & Danielssen, 1875

4 (see text)


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.[3][5][6][7]


  • Onchnesoma intermedium Murina, 1976[3][5][8]
  • Onchnesoma magnibathum Cutler, 1969[3][5][9][10]
  • Onchnesoma squamatum (Koren y Danielssen, 1875)[3][5][11]
  • Onchnesoma steenstrupii Koren y Danielssen, 1875[3][5][11]


  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. ^ a b c d e f 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. ^ a b c d e f 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. ^ a b Koren, J. and Danielssen, D.C. (1875): Bidrag de norskr Gephyreens Naturhistorie. Nytt. Magasin for Naturvidenskapene, 21:201-138.

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