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 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 site ...

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

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

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

cuttlefish Cuttlefish or cuttles are marine molluscs of the order Sepiida. They belong to the class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control of ...

, and ''

Spirula ''Spirula spirula'' is a species of deep-water squid-like cephalopod mollusk. It is the only extant member of the genus ''Spirula'', the family Spirulidae, and the order Spirulida. Because of the shape of its internal shell, it is commonly known ...

'') as well as in the eight-limbed cirrate octopuses and

vampire squid The vampire squid (''Vampyroteuthis infernalis'', lit. 'vampire squid from hell') is a small cephalopod found throughout temperate and tropical oceans in #Habitat and adaptations, extreme deep sea conditions. The vampire squid uses its Biolumines ...

. Many extinct cephalopod groups also possessed fins.

Nautilus The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in ...

es and the more familiar incirrate octopuses lack swimming fins. An extreme development of the cephalopod fin is seen in the

bigfin squid Bigfin squids are a group of rarely seen cephalopods with a distinctive morphology. They are placed in the genus ''Magnapinna'' and family Magnapinnidae. Although the family is known only from larval, paralarval, and juvenile specimens, some a ...

of the family

Magnapinnidae Bigfin squids are a group of rarely seen cephalopods with a distinctive morphology. They are placed in the genus ''Magnapinna'' and family Magnapinnidae. Although the family is known only from larval, paralarval, and juvenile specimens, some a ...

. 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 * Dorsal c ...

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. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...

(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 modifyin ...

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

gladius ''Gladius'' () is a Latin word meaning "sword" (of any type), but in its narrow sense it refers to the sword of ancient Roman foot soldiers. Early ancient Roman swords were similar to those of the Greeks, called '' xiphe'' (plural; singular ''xi ...

), 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 might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definitio ...

(as in ''

Grimalditeuthis ''Grimalditeuthis bonplandi'' is a squid named after the Grimaldi family, reigning house of Monaco. Prince Albert I of Monaco was an amateur teuthologist who pioneered the study of deep sea squids by collecting the 'precious regurgitations' of ...

''). ''Grimalditeuthis'' and larval ''

Chiroteuthis ''Chiroteuthis'' is a genus of chiroteuthid squid, comprising two subgenera. The hectocotylus is absent from all members of the genus; instead, a penis extending from the mantle opening is utilised. The genus is characterised by enlarged, li ...

'' are unusual in that they possess a pair of flotation devices or "secondary fins" attached to the tail. The

(''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 egg to adult. The term can also be used to refer to the stu ...

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

Trachyteuthis ''Trachyteuthis'' is a genus of fossil cephalopod, comprising five species: ''T. hastiformis'', ''T. latipinnis'', ''T. nusplingensis'', ''T. teudopsiformis'', ''T. covacevichi'' and ''T. chilensis''. Taxonomy The taxonomic placement of ''Tr ...

''.

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