The Solenogastres (less often referred to as Neomeniomorpha), commonly known as solenogasters, are a class of small, worm-like, shell-less

molluscs Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

(

Aplacophora Aplacophora is a class of small, deep-water, exclusively benthic, marine molluscs found in all oceans of the world. MolluscaBase eds. (2021). MolluscaBase. Aplacophora. Accessed through: World Register of Marine Species at: http://www.marinespec ...

), the other class being the

Caudofoveata Caudofoveata is a small class within the phylum Mollusca, also known as Chaetodermomorpha. The class is often combined with Solenogastres and termed Aplacophora, but some studies have cast doubt on the monophyly of this group. Anatomy Caudof ...

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Chaetodermomorpha Caudofoveata is a small class within the phylum Mollusca, also known as Chaetodermomorpha. The class is often combined with Solenogastres and termed Aplacophora, but some studies have cast doubt on the monophyly of this group. Anatomy Caudofov ...

).MolluscaBase eds. (2021). MolluscaBase. Solenogastres. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=2094 on 2021-04-14 Some recent literature and recent molecular evidence, indicates that the Aplacophora may be

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

, and therefore some taxonomists may divide Solenogastres and Caudofoveata into separate classes.

Morphology

In contrast to many other mollusc classes, aplacophorans have no shell, and are instead covered by

aragonitic Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation from ...

sclerites A sclerite (Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly ...

(

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

spicule Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

s), which can be solid or hollow. These spicules can be arranged perpendicular to one another within the cuticle to form a skeleton, stick up to form a palisade, or can lie flat against the cuticle. 80% of solenogaster

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

have a

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...

, while in others it is secondarily lost. The radula may bear one or more teeth per row; where there is more than one tooth, there is no central radular tooth. The radula grows by dividing existing teeth in two, or by adding a new tooth at the center of the radular row. The

salivary gland The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of min ...

s are very elaborate, and are an important characteristic for taxonomy. Next to the mouth they have a unique sense organ, the vestibulum. Solenogastres do not have true ctenidia, though their gill-like structures may resemble them.

Development

During development, many Solenogastres are covered by a spiny

scleritome A sclerite (Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly ...

comprising spines or scale-like plates. This has been likened to the

halwaxiid Halwaxiida or halwaxiids is a proposed clade equivalent to the older orders Sachitida He 1980 and Thambetolepidea Jell 1981, loosely uniting scale-bearing Cambrian animals, which may lie in the Crown group#Stem groups, stem group to molluscs or l ...

scleritome.

Sclerite A sclerite (Greek language, Greek , ', meaning "hardness, hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instea ...

s of ''

Epimenia ''Epimenia'' is a genus of cavibelonian solenogasters, a kind of shell-less, worm-like mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant spe ...

'' start out solid before developing a hollow stem that subsequently solidifies. Solenogastres can be found in a diverse range of habitats across the world, from the coast to the deep ocean.

Ecology

Diet

Solenogastres feed on

cnidaria Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...

and

ctenophores Ctenophora (; : ctenophore ) is a phylum of marine invertebrates, commonly known as comb jellies, that marine habitats, inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs ...

, either sucking their bodily fluids or eating their tissue. They do not use their radulae to rasp prey, as some other molluscs do.

Phylogeny

There is some uncertainty regarding the phylogenetic position of the Solenogastres. Traditionally considered to be the most basal molluscan group and the sister group to the Caudofoveata, alternatives to both of these statements have been proposed. Some molecular datasets plot Solenogastres as an outgroup to Mollusca. However, there are cryptic species which are hard to delineate due to there being a lack of multiple morphological characteristics.

Families

Acanthomeniidae Acanthomeniidae is a family of solenogaster, a shell-less worm-like mollusk.MolluscaBase eds. (2021). MolluscaBase. Acanthomeniidae Salvini-Plawen, 1978. Accessed through: World Register of Marine Species at: http://marinespecies.org/aphia.php?p ...

Salvini-Plawen, 1978 *

Amphimeniidae Amphimeniidae is a family of solenogaster The Solenogastres (less often referred to as Neomeniomorpha), commonly known as solenogasters, are a class of small, worm-like, shell-less molluscs ( Aplacophora), the other class being the Caudofovea ...

Salvini-Plawen, 1972 * Apodomeniidae Kocot, Todt, N. T. Mikkelsen & Halanych, 2019 *

Dondersiidae Dondersiidae is a family of molluscs belonging to the order Pholidoskepia The Pholidoskepia are one of the three orders of solenogaster. It is considered an alternate representation for the class Solenogastres. MolluscaBase eds. (2021). Mollu ...

Simroth, 1893 *

Drepanomeniidae Drepanomeniidae is a family of solenogaster, a kind of shell-less, worm-like, marine mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant spec ...

Salvini-Plawen, 1978 *

Epimeniidae Epimeniidae is a family of solenogaster The Solenogastres (less often referred to as Neomeniomorpha), commonly known as solenogasters, are a class of small, worm-like, shell-less molluscs ( Aplacophora), the other class being the Caudofoveata ...

Salvini-Plawen, 1978 *

Gymnomeniidae Gymnomeniidae is a family of molluscs belonging to the order Pholidoskepia The Pholidoskepia are one of the three orders of solenogaster. It is considered an alternate representation for the class Solenogastres. MolluscaBase eds. (2021). Moll ...

Odhner, 1920 *

Hemimeniidae Hemimeniidae is a family of molluscs Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, mak ...

Salvini-Plawen, 1978 *

Heteroherpiidae ''Heteroherpia'' is a genus of solenogaster The Solenogastres (less often referred to as Neomeniomorpha), commonly known as solenogasters, are a class of small, worm-like, shell-less molluscs ( Aplacophora), the other class being the Caudofov ...

Salvini-Plawen, 1978 *

Imeroherpiidae Imeroherpiidae is a family of solenogaster The Solenogastres (less often referred to as Neomeniomorpha), commonly known as solenogasters, are a class of small, worm-like, shell-less molluscs ( Aplacophora), the other class being the Caudofove ...

Salvini-Plawen, 1978 *

Lepidomeniidae Lepidomeniidae is a family of molluscs belonging to the order Pholidoskepia. Genera: * '' Lepidomenia'' Kowalevsky, 1883 * '' Nierstrassia'' Heath, 1918 * ''Tegulaherpia ''Tegulaherpia'' is a genus of pholidoskepian solenogasters, shell-less, ...

Pruvot, 1902 *

Macellomeniidae Macellomenia is a genus of solenogaster The Solenogastres (less often referred to as Neomeniomorpha), commonly known as solenogasters, are a class of small, worm-like, shell-less molluscs ( Aplacophora), the other class being the Caudofoveata ...

Salvini-Plawen, 1978 *

Meiomeniidae Meiomeniidae is a family of molluscs belonging to the order Pholidoskepia. Genera: * ''Meioherpia'' Salvini-Plawen, 1985 * ''Meiomenia'' Morse, 1979 References

Pholidoskepia Taxa described in 1985 {{solenogaster-stub ...

Salvini-Plawen, 1985 * Neomeniidae Ihering, 1876 *

Notomeniidae Notomeniidae is a family of solenogaster, a kind of shell-less, worm-like, marine mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species ...

Salvini-Plawen, 2004 *

Phyllomeniidae Phyllomeniidae is a family of molluscs belonging to the order Sterrofustia. Genera: * ''Harpagoherpia'' Salvini-Plawen, 1978 * ''Lituiherpia'' Salvini-Plawen, 1978 * ''Ocheyoherpia'' Salvini-Plawen, 1978 * ''Phyllomenia'' Thiele, 1913 * ''Plica ...

Salvini-Plawen, 1978 *

Proneomeniidae Proneomeniidae is a family of uncommon molluscs in the class Solenogastres The Solenogastres (less often referred to as Neomeniomorpha), common name, commonly known as solenogasters, are a class of small, worm-like, shell-less Mollusca, mollus ...

Mitchell, 1892 *

Pruvotinidae ''Pruvotinidae'' is a diverse Taxonomy (biology), taxonomic family (biology), family of cavibelonian solenogasters, shell-less, worm-like marine (ocean), marine mollusks. Genera Subfamily Eleutheromeniinae Salvini-Plawen, 1978 * ''Eleutheromenia ...

Heath, 1911 * Rhipidoherpiidae Salvini-Plawen, 1978 * Rhopalomeniidae Salvini-Plawen, 1978 *

Sandalomeniidae Sandalomenia is a genus of solenogaster The Solenogastres (less often referred to as Neomeniomorpha), commonly known as solenogasters, are a class of small, worm-like, shell-less molluscs ( Aplacophora), the other class being the Caudofoveata ...

Salvini-Plawen, 1978 * Simrothiellidae Salvini-Plawen, 1978 *

Strophomeniidae Strophomeniidae is a family of solenogaster, a kind of shell-less, worm-like, marine (ocean), marine mollusk.MolluscaBase eds. (2021). MolluscaBase. Strophomeniidae Salvini-Plawen, 1978. Accessed through: World Register of Marine Species at: http ...

Salvini-Plawen, 1978 *

Syngenoherpiidae Syngenoherpiidae is a family of solenogaster, a shell-less worm-like mollusk. MolluscaBase eds. (2021). MolluscaBase. Syngenoherpiidae Salvini-Plawen, 1978. Accessed through: World Register of Marine Species at: http://marinespecies.org/aphia.php ...

Salvini-Plawen, 1978 ;Unassigned in Solenogastres * '' Pholidoherpia'' Salvini-Plawen, 1978 * ''

Rhabdoherpia ''Rhabdoherpia'' is a genus of solenogaster of uncertain relationship within the order Sterrofustia The Sterrofustia are one of the three orders of solenogaster. The status of this order is uncertain, as it is deemed not monophyletic. Mollus ...

'' Salvini-Plawen, 1978 ;Synonyms: * Superorder Aplotegmentaria (not monophyletic) ** Myzomeniidae Thiele, 1894: synonym of

Simroth, 1893 * Superorder Pachytegmentaria (not monophyletic) ** Parameniidae Simroth, 1893: synonym of

Heath, 1911 (invalid: type genus a junior homonym) ** Pararrhopaliidae Salvini-Plawen, 1972: synonym of

Heath, 1911 ** Perimeniidae Nierstrasz, 1908: synonym of

Heath, 1911 ** Proneomenidae Mitchell, 1892: synonym of

Mitchell, 1892 ** Pruvotiniidae Heath, 1911: synonym of

Heath, 1911 (incorrect original spelling) ** Solenopodidae Koren & Danielssen, 1877: synonym of Neomeniidae Ihering, 1876 ** Wireniidae Salvini-Plawen, 1978: synonym of

Odhner, 1920

Images

Morphology

Development

Ecology

Diet

Phylogeny

Families

Images

References

Further reading