Dorsal (left) and ventral aspects of a mature female Grimpoteuthis innominata (73 mm ML).
Cirrate octopuses possess a well-developed internal shell that supports their muscular swimming fins. This is in contrast to the more familiar, finless, incirrate octopuses, in which the shell remnant is either present as a pair of stylets or absent altogether.[1]
The cirrate shell is quite unlike that of any other living cephalopod group and has its own dedicated set of descriptive terms.[2][3] It is usually roughly arch- or saddle-shaped and is rather soft, being similar in consistency to cartilage.[4] Each of the eight extant cirrate genera is characterised by a distinct shell morphology:[5]
Cirroteuthidae
Cirroteuthis — saddle-shaped, with large wings
Cirrothauma — butterfly-shaped
Opisthoteuthidae
Cirroctopus — V-shaped, lateral wings tapering to fine points
Cryptoteuthis — U-shaped, each lateral wing ending in broad lobe with pointed projection[6]
Opisthoteuthis — U-shaped, lateral wings usually tapering to fine points but termination complex in certain species[7]
Stauroteuthidae
Stauroteuthis — U-shaped
The comparatively simple shells of Opisthoteuthidae and Stauroteuthidae are thought to approximate the ancestral shape, with those of Cirroteuthidae being more derived.[8] The shell of Cirroctopus appears transitional in form between those of incirrate octopuses and other cirrates, and resembles the reduced shell of the Late Cretaceous Palaeoctopus newboldi.[8] The paired, rod-shaped stylets of incirrates are evolutionarily derived from the lateral wings and horns of the cirrate shell.[8]
^Fuchs, D., C. Ifrim & W. Stinnesbeck (2008). A new Palaeoctopus (Cephalopoda: Coleoidea) from the Late Cretaceous of Vallecillo, north-eastern Mexico, and implications for the evolution of Octopoda. Palaeontology51(5): 1129–1139. doi:10.1111/j.1475-4983.2008.00797.x
^Young, R.E., M. Vecchione & K.M. Mangold (1999). Cephalopoda Glossary. Tree of Life Web Project.
^Young, R.E., M. Vecchione & K.M. Mangold (2002). Cirrate Shell Terminology. Tree of Life Web Project.
^Vecchione, M., K.M. Mangold & R.E. Young (2010). Cirrata Grimpe, 1916. Tree of Life Web Project.
^Collins, M.A. & R. Villanueva (2006). Taxonomy, ecology and behaviour of the cirrate octopods. In: Gibson, R.N., R.J.A. Atkinson & J.D.M. Gordon (eds.) Oceanography and Marine Biology: An Annual Review. Aberdeen University Press, Aberdeen. pp. 277–322.
^Collins, M., R. Villanueva & R.E. Young (2008). Cryptoteuthis Collins, 2004. Tree of Life Web Project.
^Villanueva, R., R.E. Young & M. Vecchione (2008). Opisthoteuthis Verrill 1883. Tree of Life Web Project.
^ abcBizikov, V.A. (2004). Evolution of shell in Octopodiformes (Cephalopoda) Archived 2013-10-21 at the Wayback Machine. In: Abstracts of the conference Mollusks of the Northeastern Asia and Northern Pacific: Biodiversity, Ecology, Biogeography and Faunal History. October 4–6, 2004, Vladivostok, Russia. pp. 21–23.
Cirrate octopuses possess a well-developed internal shell that supports their muscular swimming fins. This is in contrast to the more familiar, finless...
hardened secretion of stony corals and the prominent mollusc shell shared by snails, clams, tusk shells, chitons and nautilus. Some vertebrate animals, such as...
A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea...
organic–inorganic composite material produced by some molluscs as an inner shell layer. It is also the material of which pearls are composed. It is strong...
as cuttlefish bone, is a hard, brittle internal structure (an internal shell) found in all members of the family Sepiidae, commonly known as cuttlefish...
Cirrate octopuses have a small, internal shell and two fins on their head, while their sister suborder Incirrina has neither. The fins of cirrate octopods...
in biological systems, such as the formation of stromatolites or mollusc shells (see Biomineralization). Calcification can manifest itself in many ways...
Ammonoidea. Cuttlefish, squid, spirula, vampire squid, and cirrate octopuses have small internal shells. Females of the octopus genus Argonauta secrete a specialised...
and cuttlefish) have an internalized vestigial aragonite/calcite-chitin shell known as gladius or cuttlebone, which can serve as muscle attachments but...
Diatomaceous earth consists of the fossilized remains of diatoms, a type of hard-shelled microalgae. It is used as a filtration aid, mild abrasive in products including...
these tissues form a protective shield or structural support. Bone, mollusc shells, deep sea sponge Euplectella species, radiolarians, diatoms, antler bone...
Coccolithophore shells Many protists have protective shells or tests, usually made from silica (glass) or calcium carbonate (chalk). Protists are a diverse...
animal has fimbriated head lobes and side lobes that are fimbriated and cirrated. The radula has small median teeth, and the lateral teeth are single and...
vertebrates. These minerals often form structural features such as sea shells and the bone in mammals and birds. Organisms have been producing mineralized...
shells. These animals may have been molluscs or worm-like Sipuncula. Other molluscan univalved shells have been found in Canada. Some bivalve shells have...
huxleyi) and cover the cell surface arranged in the form of a spherical shell, called a coccosphere. Coccolithophores are spherical cells about 5–100...
The gastropod shell is part of the body of a gastropod or snail, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical...
calcifying organisms on the planet, covering themselves with a calcium carbonate shell called a coccosphere. However, the reasons they calcify remain elusive....
Naked amoeba (i. e. not testate) showing food vacuoles and ingested diatom Shell or test of a testate amoeba, Arcella sp. Xenogenic testate amoeba covered...
other calcifying marine invertebrates. The resulting structures, such as shells, skeletons, and coral reefs, function as protection, support, and shelter...
functional biominerals, such as endoskeletons and exoskeletons, protective shells, or teeth, had been a significant step in animal evolution. Calcium carbonate...
granular ectoplasm for catching food and other uses; and commonly an external shell (called a "test") of diverse forms and materials. Tests of chitin (found...
Global Information