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Cephalopod fin
Cephalopod fins, sometimes known as wings,〔Young, R.E., M. Vecchione & K.M. Mangold (1999). (Cephalopoda Glossary ). Tree of Life Web Project.〕 are paired flap-like locomotory appendages. They are found in ten-limbed cephalopods (including squid, bobtail squid, cuttlefish, and ''Spirula'') as well as in the eight-limbed cirrate octopuses and vampire squid. Many extinct cephalopod groups also possessed fins. Nautiluses and the more familiar incirrate octopuses lack swimming fins. An extreme development of the cephalopod fin is seen in the bigfin squid of the family Magnapinnidae.〔Vecchione, M. & R.E. Young (1998). The Magnapinnidae, a newly discovered family of oceanic squid (Cephalopoda: Oegopsida). ''South African Journal of Marine Science'' 20(1): 429–437. 〕
Fins project from the mantle and are often positioned dorsally. In most cephalopods, the fins are restricted to the posterior end of the mantle, but in cuttlefish and some squid they span the mantle's entire length.
Fin attachment varies greatly among cephalopods, though in all cases it involves specialised fin cartilage (which reaches its greatest development in Octopodiformes).〔Young, R.E., M. Vecchione & K.M. Mangold (2000). (Cephalopoda Fin Cartilage ). Tree of Life Web Project.〕 A fin may be attached to the internal shell or shell remnant (such as the gladius), to the opposite fin, to the mantle, or a combination of these.〔Young, R.E., M. Vecchione & K.M. Mangold (2001). (Cephalopod Fin Attachment ). Tree of Life Web Project.〕
==Tail and secondary fins==
Certain squid species possess a tail, which is an extension of the body past the fins.〔 The tail may be said to start at "the point where a hypothetical line, continuous with the broad posterior edge of the fin, crosses the midline of the body".〔 This tail may be lost with age (as in most paralarval chiroteuthids)〔Vecchione, M., B.H. Robison & C.F.E. Roper (1992). ''Proceedings of the Biological Society of Washington'' 105(4): 683–692.〕 or remain through sexual maturity (as in ''Grimalditeuthis''). ''Grimalditeuthis'' and larval ''Chiroteuthis'' are unusual in that they possess a pair of flotation devices or "secondary fins" attached to the tail. The vampire squid (''Vampyroteuthis infernalis'') also has two pairs of fins during a brief period of its ontogeny, and secondary fins have been reported in the extinct ''Trachyteuthis''.〔Donovan, D.T., L.A. Doguzhaeva & H. Mutvei (2003). ''Berliner Paläobiologische Abhandlungen'' 3: 91–99.〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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