Note

Decapodiform Fin Shapes

Richard E. Young, Michael Vecchione, and Katharina M. Mangold (1922-2003)

Cephalopoda Glossary


Fin shapes are difficult to define as the shape of some fins bridge the gaps between standard shapes. Use this character cautiously.


Sagittate fins

Sagittate fins are probably the most common shape found in squids. These fins have anterior free fin-lobes, a relatively sharp lateral angle and posterior elongate fin with a concave posterolateral margin.

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Click on an image to view larger version & data in a new window

Figure. A - Abralia andamanica, ventral and dorsal views,, modified from Voss, 1963. B - Gonatus fabricii, dorsal view, modified from Naef, 1921. C - Onychoteuthis borealijaponicus, ventral view, modified from Young, 1972.


Rhomboid fins

Rhomboid fins are similar to sagittate fins except that the posterolateral fin margin is not concave but straight.

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Click on an image to view larger version & data in a new window

Figure. A - Loligo forbesi modified from Naef, 1921/23. B - Berryteuthis anonychus modified from Pearcy and Voss, 1963.


Circular/elliptical fins

Circular/elliptical fins nearly, or complete, lack anterior and posterior fin-lobes and have broadly rounded or no lateral fin angles. The circular to elliptical outline describes the shape of the combined fins.

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Click on an image to view larger version & data in a new window

Figure. A - Discoteuthis laciniosa modified from Young and Roper, 1969. B - Liocranchia reinhardti modified from Voss, 1963. C - Joubiniteuthis portieri modified from Young and Roper, 1969. D - Chiroteuthis picteti modified from Voss, 1963.


Lanceolate fins

Lanceolate fins are elongate in the anterior-posterior direction, lack posterior fin lobes, usually have reduced anterior fin lobes and lack a lateral angle. The resulting shape is similar to the head of a lance.

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Click on an image to view larger version & data in a new window

Figure. Galiteuthis glacialis modified from McSweeny, 1978.


Ear-shaped fins

Ear-shaped fins have both anterior and posterior fin lobes and lack lateral angles. The fins usually are completely separate from one another.

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Click on an image to view larger version & data in a new window

Figure. A - Idiosepius pygmaeus, modified from Voss, 1963. B - Bathyteuthis abyssicola modified from Roper, 1969. C - Pyroteuthis addolux modified from Young, 1972. D - Bathothauma lyromma modified from Chun, 1910. E - Iridoteuthis iris, modified from Naef, 1921-23.


Ribbed fins

Ribbed fins have a series of independent muscle bundles within each fin that look like a series of ribs or teeth on a comb. The fin is long and slender and without lateral angles.

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Click on an image to view larger version & data in a new window

Figure. Side view of Chtenopteryx, modified from Okutani, 1974.


Lobate fins

Lobate fins have a posterior fin-lobe and lack an anterior one. No lateral angle exists and each fin is often much longer than broad.

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Click on an image to view larger version & data in a new window

Figure. A - Dorsal view of Neoteuthis sp., modified from Young, 1972. B - Ventral view of Alluroteuthis antarcticus, modified from Roper, et al., 1969.


Skirt-like fins

Skirt-like fins are narrow and extend along the lateral margins of the mantle. They have free anterior and posterior lobes and lack lateral angles..

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Click on an image to view larger version & data in a new window

Figure. Dorsal view of Sepia orbigyana, modified from Naef, 1921-23.

References

Chun, C. 1910. Die Cephalopoden. Oegopsida. Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition, "Valdivia" 1898-1899, 18: 1-522 + Atlas.

McSweeny, E. S. 1978. Systematics and morphology of the Antarctic cranchiid squid Galiteuthis glacialis (Chun). Antarctic Research Series, 27: 1-39.

Okutani, T. 1981. Two new species of the squid genus Onykia from the tropical Indian Ocean (Cephalopoda, Onychoteuthidae). Bull. Nat. Sci. Mus., Tokyo, Ser. A. 7: 155-163.

Pearcy, W. G. and G. L. Voss. 1963. A new species of gonatid squid from the Northeastern Pacific. Proc. Biol. Soc. Wash., 76: 105-112.

Roper, C.F.E. 1969. Systematics and zoogeography of the worldwide bathypelagic squid Bathyteuthis (Cephalopoda: Oegopsida). Bulletin of the United States National Museum, 291:1-210.

Roper, C. F. E., R. E. Young and G. L. Voss (1969). An illustrated key to the families of the order Teuthoidea. Smiths. contr. zool., 13:1-32.

Voss, G. L. 1963. Cephalopods of the Philippine Islands. Bull. U. S. Nat. Mus., 234: 1-180.

Young, R. E. 1972. The systematics and areal distribution of pelagic cephalopods from the seas off Southern California. Smithson. Contr. Zool., 97: 1-159.

Young, R. E. and C. F. E. Roper (1969). A monograph of the Cephalopoda of the North Atlantic: The family Cycloteuthidae. Smithson. Contr. Zool., No. 5: 1-24.

Young, R. E. and C. F. E. Roper (1969). A monograph of the Cephalopoda of the North Atlantic: The family Joubiniteuthidae. Smithson. Contr. Zool., No. 15: 1-10.

About This Page


University of Hawaii, Honolulu, HI, USA


National Museum of Natural History, Washington, D. C. , USA

Katharina M. Mangold (1922-2003)
Laboratoire Arago, Banyuls-Sur-Mer, France

Page: Tree of Life Decapodiform Fin Shapes Authored by Richard E. Young, Michael Vecchione, and Katharina M. Mangold (1922-2003). The TEXT of this page is licensed under the Creative Commons Attribution-NonCommercial License - Version 3.0. Note that images and other media featured on this page are each governed by their own license, and they may or may not be available for reuse. Click on an image or a media link to access the media data window, which provides the relevant licensing information. For the general terms and conditions of ToL material reuse and redistribution, please see the Tree of Life Copyright Policies.

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