Myopsida is one of the four orders of squid. It consists of two

families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideal ...

: the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

'' Australiteuthis'' and the diverse and commercially important

Loliginidae Loliginidae, commonly known as pencil squids, is an aquatic family of squid classified in the order Myopsida. Taxonomy The family Loliginidae was formerly classified in the order Teuthida. Taxonomic list The classification below follows ...

(~50 species). Some

taxonomist In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are give ...

s classify this taxon as a suborder of the order Teuthida, in which case it is known as Myopsina. This reclassification is due to Myopsina and Oegopsina not being demonstrated to form a clade. A number of morphological features distinguish members of Myopsida from those of its sister group, Oegopsida. Some of the most obvious differences are found in the structure of the

eyes Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and con ...

: those of myopsid squids lack a secondary eyelid and are instead covered by a transparent corneal membrane, the opening of which is reduced to a microscopic anterior pore in most species. The arms and tentacles are ornamented with simple suckers (hooks are never present), with additional suckers usually borne on the buccal lappets. The carpal ("wrist") portion of the

tentacular club All cephalopods possess flexible limbs extending from their heads and surrounding their beaks. These appendages, which function as muscular hydrostats, have been variously termed arms, legs or tentacles. Description In the scientific l ...

lacks a locking apparatus, and a tentacle pocket is present on the head. The

funnel A funnel is a tube or pipe that is wide at the top and narrow at the bottom, used for guiding liquid or powder into a small opening. Funnels are usually made of stainless steel, aluminium, glass, or plastic. The material used in its construct ...

has no lateral adductor muscles. An internalised shell is present in the form of a well-developed

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 ...

, which is located dorsally within the mantle and extends for almost its entire length. In contrast to oegopsids, females possess accessory nidamental glands in addition to the main nidamental glands. They however lack a right

oviduct The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...

.Jereb, P. & C.F.E. Roper (2010). Squids. In: P. Jereb & C.F.E. Roper (eds.)
Cephalopods of the world. An annotated and illustrated catalogue of species known to date. Volume 2. Myopsid and Oegopsid Squids
'. FAO Species Catalogue for Fishery Purposes No. 4, Vol. 2. FAO, Rome. pp. 34–35.Vecchione, M. & R.E. Young (2008)
Myopsida Naef, 1916

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 ...

. Myopsids are found in

coastal waters The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in n ...

worldwide. They are demersal, generally feeding on or near the bottom. Adult sizes range from the dwarf '' Australiteuthis'' and '' Pickfordiateuthis'', whose males mature at less than in mantle length (ML), to the large ''

Loligo forbesii ''Loligo forbesii'' (sometimes erroneouslyBouchet, P. and S. Gofas. (2013)''Loligo forbesi'' Steenstrup, 1856.World Register of Marine Species. Accessed 5 June 2013. spelled ''forbesi''), known commonly as the veined squid and long-finned squid, ...

'', which can exceed ML.

References

Squid {{squid-stub