Cephalopod fins, sometimes known as wings,Young, R.E., M. Vecchione & K.M. Mangold (1999)
Cephalopoda Glossary

Tree of Life Web Project The Tree of Life Web Project (ToL) is an Internet project providing information about the diversity and phylogeny of life on Earth. This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The s ...

. are paired flap-like locomotory appendages. They are found in ten-limbed cephalopods (including

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

bobtail squid Bobtail squid (order Sepiolida) are a group of cephalopods closely related to cuttlefish. Bobtail squid tend to have a rounder mantle (mollusc), mantle than cuttlefish and have no cuttlebone. They have eight suckered arms and two tentacles and ar ...

cuttlefish Cuttlefish, or cuttles, are Marine (ocean), marine Mollusca, molluscs of the order (biology), suborder Sepiina. They belong to the class (biology), class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique ...

, and '' Spirula'') as well as in the eight-limbed cirrate octopuses and vampire squid. Many extinct cephalopod groups also possessed fins.

Nautilus A nautilus (; ) is any of the various species within the cephalopod family Nautilidae. This is the sole extant family of the superfamily Nautilaceae and the suborder Nautilina. It comprises nine living species in two genera, the type genus, ty ...

es 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. Fins project from the mantle and are often positioned

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

ly. 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 Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

(which reaches its greatest development in

Octopodiformes Octopodiformes is a superorder of the subclass Coleoidea, comprising the octopuses and the vampire squid. All living members of Octopodiformes have eight arms, either lacking the two tentacles of squid (as is the case in octopuses) or modifying ...

). A fin may be attached to the internal shell or shell remnant (such as the

gladius ''Gladius'' () is a Latin word properly referring to the type of sword that was used by Ancient Rome, ancient Roman foot soldiers starting from the 3rd century BC and until the 3rd century AD. Linguistically, within Latin, the word also came t ...

), to the opposite fin, to the mantle, or a combination of these. Cirroteuthis muelleri NOAA

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) or remain through

sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans, it is related to both puberty and adulthood. ''Puberty'' is the biological process of sexual maturation, while ''adulthood'', the condition of being socially recognized ...

(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 Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the ovum, egg to adult. The term can also be used to refer to t ...

, and secondary fins have been reported in the extinct '' Trachyteuthis''.

Fin morphology and placement

Cephalopod fin morphology is highly variable. The fins may be large and muscular, extending for the entire length of the mantle, or greatly reduced (sometimes less than 10% ML) and restricted to the mantle's posterior end. Fin placement in cephalopods is often termed ''normal'', ''terminal'', or ''subterminal'', depending on their position with respect to the muscular mantle.Young, R.E., M. Vecchione & K.M. Mangold (2001)
Cephalopod Fin Position

. Eight major fin shapes can be distinguished among the

Decapodiformes Decapodiformes is a superorder of Cephalopoda comprising all cephalopod species with ten limbs, specifically eight short arms and two long tentacles. It is hypothesized that the ancestral coleoid had five identical pairs of limbs, and that one ...

: sagittate (the most common shape in squid), rhomboid, circular/elliptical, lanceolate, ear-shaped, ribbed, lobate, and skirt-like.Young, R.E., M. Vecchione & K.M. Mangold (2001)
Decapodiform Fin Shapes

References

{{Cephalopod anatomy Cephalopod zootomy