The

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

Cavolinioidea is the most speciose group of

sea butterflies Sea butterflies, scientific name Thecosomata (thecosomes, "case / shell-body"), are a taxonomic suborder of small pelagic swimming sea snails. They are holoplanktonic opisthobranch gastropod mollusks. Most Thecosomata have some form of calcified ...

. They belong to the suborder

Euthecosomata ''Euthecosomata'' is a taxonomic unit used to classify sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda ...

. MolluscaBase eds. (2021). MolluscaBase. Cavolinioidea Gray, 1850 (1815). Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=411903 on 2021-03-11 Sea butterflies (thecosomata) are

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

s, so called because they swim by flapping their wing-like parapodia.

Distribution

These sea butterflies are circumglobal, carried by the sea currents to all the seas of the world.

Habitat

Cavoliniids prefer deep waters, from 100 m up to 2,000 m. They do best in warm oceanic water.

Shell description

Species in this superfamily have a

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...

, bilaterally symmetrical conical or globular shell. Identification of juveniles is difficult as the juvenile shells differ greatly from adults.

Life habits

Towards the anterior end of the animal, two parapodia (winglike flat lobules) protrude between each half of the shell. The parapodia enable these sea butterflies to float along in the water currents, using slow flapping movements. The parapodia are also covered with

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

, which produce a minute water current that pushes the

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic food to the mouth of the animal.

Reproduction

Cavoliniids have a strange sexual life. They develop from males as juveniles into

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...

s and then later convert into females. More than one male stage can occur. This bizarre-seeming, but not very uncommon phenomenon is called

protandry Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...

. (This is also common among many species of fish, some may all start as females, others species may start as males.)

Taxonomy

In 2003, the family Cavoliniidae was raised to the rank of superfamily Cavolinioidea. At the same time, the subfamilies were given the new status of families: Cavoliniidae, Cliidae, Creseidae and Cuvierinidae (''Cainozoic Research'', 2(1-2): 163-170, 2003).

2005 taxonomy

In the taxonomy of Bouchet & Rocroi (2005) several families have been categorized as subfamilies of the family Cavoliniidae and the superfamily Cavolinioidea is treated like this: * Family

Cavoliniidae The family Cavoliniidae is a taxonomic group of small floating sea snails, pelagic marine opisthobranch gastropod mollusks.Gofas, S. (2011). Cavoliniidae. Accessed through: World Register of Marine Species at http://www.marinespecies.org/ap ...

Gray, 1850 (1815) **Subfamily Cavoliinae Gray, 1850 (1815) - formerly Hyalaeidae Rafinesque, 1815 * Family Cliidae Jeffreys, 1869 - formerly Cleodoridae Gray, 1840 - nomen oblitum * Family

Creseidae Creseidae is a family of gastropods belonging to the order Pteropoda Pteropoda (common name pteropods, from the Greek meaning "wing-foot") are specialized free-swimming pelagic sea snails and sea slugs, marine opisthobranch gastropods. Most ...

Rampal, 1973 - formerly subfamily Creseinae Curry, 1982 * Family

Cuvierinidae Cuvierinidae is a family of gastropods belonging to the order Pteropoda Pteropoda (common name pteropods, from the Greek meaning "wing-foot") are specialized free-swimming pelagic sea snails and sea slugs, marine opisthobranch gastropods. Mos ...

van der Spoel, 1967 - formerly subfamily Cuvierininae van der Spoel, 1967 * † Family Sphaerocinidae A. Janssen & Maxwell, 1995 In 2005 a new family

Praecuvierinidae The Praecuvierinidae are a family of extinct, small, floating sea snails, pelagic marine opisthobranch gastropod mollusks in the superfamily Cavolinioidea. Genera * Genus '' Praecuvierina'' Janssen, 2005 ** '' Praecuvierina lura'' (Hodgki ...

Janssen, 2005 was created on evolutionary grounds. In 2020 a new family Hyalocylidae A. W. Janssen, 2020 was added. Janssen A.W. (2020). Notes on the systematics, morphology and biostratigraphy of holoplanktic Mollusca, 27. Comments on a paper discussing Pteropoda (Gastropoda, Heterobranchia) systematics, recently (2019) published in Bollettino Malacologico. Basteria. 84(1-3): 65-75. ;Families brought into synonymy: * Cleodoridae Gray, 1840: synonym of Cavoliniidae Gray, 1850 (1815) * Clioidae Jeffreys, 1869: synonym of Cliidae Jeffreys, 1869 (incorrect subsequent spelling) * Hyalaeidae Rafinesque, 1815: synonym of Cavoliniidae Gray, 1850 (1815) * Tripteridae Gray, 1850: synonym of Cliidae Jeffreys, 1869

References

* Rampal J. (2002). "Biodiversité et biogéographie chez les Cavoliniidae (Mollusca, Gastropoda, Opisthobranchia, Euthecosomata). Régions faunistiques marines" ''Zoosystema'', 24(2):209-258. * Janssen A. W. (2003). "Notes on the systematics, morphology and biostratigraphy of fossil holoplanktonic Mollusca, 13. "Considerations on a subdivision of Thecosomata, with the emphasis on genus group classification of Limacinidae" ''Cainozoic Research'', 2(1-2): 163-170. * Janssen A. W. (2006). "Notes on the systematics, morphology and biostratigraphy of fossil holoplanktonic Mollusca, 16. Some additional notes and amendments on Cuvierinidae and on classification of Thecosomata (Mollusca, Euthecosomata". ''Basteria'' 70(1-3): 67-70. {{Taxonbar, from=Q5055196 Euopisthobranchia Cavolinioidea Taxa named by John Edward Gray