Acochlidiacea, common name acochlidians, are a

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

clade of very unusual

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 with slugs, which are distinguished from snails primarily by the ...

s and sea and freshwater

slug Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a smal ...

s, aquatic

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 ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

s within the large clade Heterobranchia. Acochlidia is a variant spelling. Pseudunela cornuta

Description

These are mostly very small animals, without a shell or

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s, distinguished by the visceral mass being sharply set off from the rest of the body. Being a small group with only 30 species worldwide known in 2010, and 32 species described in 2011, and 33 in 2012 (+9 undescribed '' Pontohedyle'' species), these slugs are morphologically and biologically highly aberrant and diverse, comprising a series of unusual characters (e.g. secondary gonochorism, lack of copulatory organs, asymmetric

radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs 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 ...

e). Most acochlidians live interstitially in marine sands, while some have conquered limnic systems (uniquely within opisthobranch gastropods).

Taxonomy

Nils Hjalmar Odhner established this taxon as a family in 1937, when he created the families

Microhedylidae Parhedylidae are a taxonomic family of sea slugs, marine gastropod mollusks in the superfamily Parhedyloidea. MolluscaBase eds. (2021). MolluscaBase. Parhedylidae Thiele, 1931. Accessed through: World Register of Marine Species at: http://www.m ...

and Acochlidiidae. In 1939, he treated this taxon as an order. Rankin (1979)Rankin J. J. (1979). "A freshwater shell-less mollusc from the Caribbean: structure, biotics, and contribution to a new understanding of the Acochlidioidea". ''

Royal Ontario Museum The Royal Ontario Museum (ROM) is a museum of art, world culture and natural history in Toronto, Ontario, Canada. It is one of the largest museums in North America and the largest in Canada. It attracts more than one million visitors every year ...

, Life Sciences Contributions'' 116: 123 pp., page 83. treated this taxon as an order, the order Acochlidioidea. Salvini-Plawen (1983) wrote this taxon as Acochlidiomorpha. Anderson (1992) treated this taxon as the order Acochlidiida. Burn in Beesley et al. (1998), wrote this taxon as the order Acochlidea. Wawra (1987) and various authors (2007–2010)Schrödl M. & Neusser T. P. (2010). "Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)". ''

Zoological Journal of the Linnean Society The ''Zoological Journal of the Linnean Society'' is a monthly peer-reviewed scientific journal covering zoology published by Oxford University Press on behalf of the Linnean Society. The editor-in-chief is Maarten Christenhusz (Linnean Society). ...

'' 158: 124–154. . spelled this taxon as Acochlidia. Three families ( Hedylopsidae,

and Acochlidiidae) are classically recognized. Two controversial classifications (Rankin 1979,

Starobogatov Yaroslav Igorevich Starobogatov (russian: Ярослав Игоревич Старобогатов; 13 July 1932 – 3 December 2004) was a Russian zoologist, professor and chief scientist at the Zoological Institute of the Russian Academy of Scie ...

1983) Starobogatov Ya. I. (1983). "Sistema otriada Acochlidiiformes ystem of the order Acochlidiiformes" ''Vsesoiuznoe soveshchanie po izucheniiu molliuskov'', Leningrad, 7: 30–32. have been proposed recently, but they have not been evaluated since. An alternative classification by Burn (in Beesley et al., 1998) for the Australian species recognizes 2 superfamilies and 5 families. Pseudunela cornuta 2

The Acochlidia, a traditional "order" of the Opisthobranchia since their establishment by Odhner have formed one of the unsolved mysteries within Euthyneura. Their

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...

is widely accepted especially since a proposed sister group relationship of the acochlidian family Ganitidae with Sacoglossa (based on the dagger-shaped radula teeth) could be rejected based on a comprehensive parsimony analysis of morphological characters. During the last years a series of studies have redescribed key acochlidian taxa in great detail, including

3D reconstruction In computer vision and computer graphics, 3D reconstruction is the process of capturing the shape and appearance of real objects. This process can be accomplished either by active or passive methods. If the model is allowed to change its shape i ...

s, and added considerably to the morphological and biological knowledge of this previously little understood group. Most recent morphological analyses suggested a common origin with either the equally enigmatic Rhodopemorpha, the diaphanid cephalaspidean ''

Toledonia ''Toledonia'' is a genus of sea snails, marine gastropod molluscs in the family Cylichnidae.Bouchet, P.; Gofas, S. (2014). Toledonia Dall, 1902. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxde ...

'', or with runcinid or philinoid cephalaspideans. Molecular markers independent from direct ecological pressures suggested an unresolved basal opisthobranch origin for Acochlidia (based on nuclear 18S rRNA and 28S rRNA) (Vonnemann et al. 2005). A first combined multi-gene dataset led to the surprising result of Acochlidia clustering in a pulmonate relationship, united in a clade with

Pyramidelloidea Pyramidelloidea is a superfamily of mostly very small sea snails, marine gastropod mollusks and micromollusks within the clade Panpulmonata. This is a voluminous taxon: above the species level close to 400 named taxa are referred to this gast ...

Amphiboloidea Amphiboloidea is a Taxonomy (biology), taxonomic superfamily of air-breathing land snails. Distribution Amphibolids are found in Indo-Pacific intertidal mangrove, saltmarsh and estuarine mudflat habitats. Taxonomy 2005 taxonomy According ...

and

Eupulmonata Eupulmonata is a taxonomic clade of air-breathing snails. The great majority of this group are land snails and slugs, but some are marine and some are saltmarsh snails that can tolerate salty conditions. Linnean taxonomy *Suborder Eupulmonat ...

. However, only three derived acochlids were included into analysis prior to 2010, with partially missing data.

2005 taxonomy

The taxonomy of Bouchet & Rocroi (2005) tentatively follows Starobogatov (1983), but they have downgraded his taxonomic ranks (suborders to superfamilies, superfamilies to families). The group Acochlidiacea is arranged as follows: *Superfamily

Acochlidioidea Acochlidiidae are a taxonomic family of shell-less freshwater gastropods (one of them ''Palliohedyle weberi'' lives in brackish water),Schrödl M. & Neusser T. P. (2010). "Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: O ...

**Family Acochlidiidae *Superfamily

Hedylopsoidea Hedylopsoidea was defined as a taxonomic superfamily of sea slugs, mostly marine gastropod mollusks within the informal group Opisthobranchia according to the taxonomy of Bouchet & Rocroi (2005). Schrödl & Neusser (2010)Schrödl M. & Neusser ...

**Family Hedylopsidae **Family Ganitidae **Family

Livorniellidae Parhedylidae are a taxonomic family of sea slugs, marine gastropod mollusks in the superfamily Parhedyloidea. MolluscaBase eds. (2021). MolluscaBase. Parhedylidae Thiele, 1931. Accessed through: World Register of Marine Species at: http://www.m ...

**Family

Minicheviellidae ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (2010) ...

**Family

Parhedylidae Parhedylidae are a taxonomic family of sea slugs, marine gastropod mollusks in the superfamily Parhedyloidea. MolluscaBase eds. (2021). MolluscaBase. Parhedylidae Thiele, 1931. Accessed through: World Register of Marine Species at: http://www.m ...

**Family Tantulidae *Superfamily Palliohedyloidea **Family Palliohedylidae *Superfamily

Strubellioidea According to the taxonomy of Bouchet & Rocroi (2005), Strubellioidea was a taxonomic superfamily of sea slugs, mostly marine gastropod mollusks within the informal group Opisthobranchia. However, Schrödl & Neusser (2010)Schrödl M. & Neusser ...

**Family

Strubelliidae ''Strubellia paradoxa'' is a species of freshwater slug, a shell-less freshwater gastropod,Strong E. E., Gargominy O., Ponder W. F. & Bouchet P. (2008). "Global Diversity of Gastropods (Gastropoda; Mollusca) in Freshwater". ''Hydrobiologia'' 595 ...

**Family Pseudunelidae

2010 taxonomy

A first comprehensive cladistic analysis of their

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

has been established by Schrödl & Neusser (2010), but the identity of their sister group remained uncertain. Morphology-based analyses by Schrödl & Neusser, demonstrated that Acochlidia usually group with other mesopsammic (they live in interstitial spaces of marine sands) taxa, if any were included (i.e. with the sacoglossan '' Platyhedyle'', the rhodopemorph ''

Rhodope Rhodope may refer to: * Rhodope (mythology), a figure of Greek mythology * Rhodope Mountains, in Bulgaria and Greece * Rhodope (regional unit), of Greece * Rhodope (province), a Roman and Byzantine province * 166 Rhodope, an asteroid * Rhodope (genu ...

'' or the cephalaspideans '' Philinoglossa'' or '' Philine exigua''). Thus, it is likely that convergent adaptations to the interstitial habitat mask the truly phylogenetic signals. Schrödl & Neusser (2010) split Acochlidiacea into two (unranked) taxa and into six families like this:

Hedylopsacea

Hedylopsacean Acochlidiacea, whose evolution involves several habitat shifts from marine interstitial to amphibious or freshwater benthic habitats, possess complex excretory and reproductive systems. (unranked) Hedylopsacea has no superfamilies defined: * Acochlidiidae: ''

Acochlidium ''Acochlidium'' is a genus of freshwater slugs, an aquatic gastropod molluscs in the family Acochlidiidae. ''Acochlidium'' species have no shell. Species Species within the genus ''Acochlidium'' include: * ''Acochlidium amboinense'' Strubell, ...

'', ''

Palliohedyle ''Palliohedyle'' is a genus of gastropods belonging to the family Acochlidiidae. Species: *''Palliohedyle sutteri'' *''Palliohedyle weberi ''Palliohedyle'' is a genus of gastropods belonging to the family Acochlidiidae. Species: *''Pallio ...

'', including ''

Strubellia ''Strubellia paradoxa'' is a species of freshwater slug, a shell-less freshwater gastropod,Strong E. E., Gargominy O., Ponder W. F. & Bouchet P. (2008). "Global Diversity of Gastropods (Gastropoda; Mollusca) in Freshwater". ''Hydrobiologia'' 595 ...

'' * Pseudunelidae: with the only genus ''

Pseudunela ''Pseudunela'' is a genus of minute sea slugs, acochlidians, shell-less marine or temporary brackish or brackish gastropod mollusks in the clade Acochlidiacea. ''Pseudunela'' is the only genus in the family Pseudunelidae. ''Pseudunela'' is the ...

'' * Hedylopsidae: with the only genus ''

Hedylopsis Hedylopsis is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Hedylopsidae has been classified within the superfamily Hedylopsoidea in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusse ...

'' * Tantulidae: with the only species '' Tantulum elegans''

Microhedylacea

Microhedylacean Acochlidiacea are exclusively found in interstitial spaces in sediment, and show a tendency toward reduction of complexity in major organ systems. (unranked) Microhedylacea has no superfamilies defined: * Asperspinidae: with the only genus ''

Asperspina ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (2010) ...

'' – junior synonym:

s.l.: '' Pontohedyle'', ''

Parhedyle ''Parhedyle'' is a genus of gastropods belonging to the family Microhedylidae. The species of this genus are found in Europe. Species: *''Parhedyle cryptophthalma'' *''Parhedyle odhneri'' *''Parhedyle tyrtowii ''Parhedyle'' is a genus of ga ...

'', '' Microhedyle'' – including Ganitidae: '' Ganitus'' and '' Paraganitus''. Inclusion of Ganitidae within Microhedylidae requires further research and higher statistical support. A multi-locus molecular study by Jörger et al. (2010), included six out of seven acochlidian families. It confirmed Acochlidiacea in a pulmonate relationship, as sister to Eupulmonata. Euthyneura, Opisthobranchia and Pulmonata as traditionally defined were found non-monophyletic. The enigmatic amphibious and insectivorous

Aitengidae ''Aiteng'' is a genus comprising three species of sea slug, ''A. ater'' and ''A. mysticus'' being found in intertidal zones while ''A. marefugitus'' is fully terrestrial. ''Aiteng'' is the only genus in the family Aitengidae. The generic name ' ...

clusters within Acochlidiacea, as sister to meiofaunal and brackish Pseudunelidae and limnic Acochlidiidae. Inclusion of this small acochlidian group resulted in redefinition of major groups within Heterobranchia, that has led to creation of the new clades Euopisthobranchia and Panpulmonata.

2016 taxonomy

Two more families were established. Both include slugs that are unusual among acochlidians for their anatomy and habitat (amphibious, terrestrial, or benthic in deeper waters): *

Swennen & Buatip, 2009 * Bathyhedylidae Neusser, Jörger, Lodde-Bensch, Strong & Schrödl, 2016Neusser T. P., Jörger K. M., Lodde-Bensch E., Strong E. E. & Schrödl M. (2016). "The unique deep sea - land connection: Interactive 3D visualization and molecular phylogeny of ''Bathyhedyle boucheti'' n. sp. (Bathyhedylidae n. fam.) - the first panpulmonate slug from bathyal zones". ''PeerJ'' 4: e2738. .

Phylogeny

There is no fossil record of Acochlidiacea. Application of a

molecular clock The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleoti ...

allowed estimation of divergence times for these groups. The split between

and Acochlidiacea took place in the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...

, between the Triassic and Jurassic periods. The diversification of Acochlidia is estimated to have happened in the Jurassic with the split between Hedylopsacea and Microhedylacea.

Cladogram

A cladogram showing phylogenetic relations of some genera and species within Acochlidiacea:

Ecology

The life cycle of Acochlidiacea is poorly known. With a typically low reproductive output in Acochlidiacea (max. of 40 eggs in '' Pontohedyle milaschewitchii''), free veliger larvae are assumed to stay in the interstices of the sand grains rather than entering the water column thereby avoiding long distance dispersal. Fertilized eggs are attached to sand grains and might promote dispersal via current driven sediment transport along shorelines.

Overview of species

# ''

Hedylopsis spiculifera Hedylopsis is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Hedylopsidae has been classified within the superfamily Hedylopsoidea in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusse ...

'' (Kowalevsky, 1901) (Hedylopsidae) – marine # ''

Hedylopsis ballantinei Hedylopsis is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Hedylopsidae has been classified within the superfamily Hedylopsoidea in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusse ...

'' Sommerfeldt & Schrödl, 2005 (Hedylopsidae) – marine # ''

Pseudunela cornuta ''Pseudunela cornuta'' is a species of minute sea slug, an acochlidian, a shell-less marine and temporarily brackishNeusser T. P., Jörger K. M. & Schrödl M. (2011). "Cryptic Species in Tropic Sands – Interactive 3D Anatomy, Molecular Ph ...

'' (Challis, 1970) (Pseudunelidae) – marine and temporary brackish # ''

Pseudunela eirene ''Pseudunela'' is a genus of minute sea slugs, acochlidians, shell-less marine or temporary brackish or brackish gastropod mollusks in the clade Acochlidiacea. ''Pseudunela'' is the only genus in the family Pseudunelidae. ''Pseudunela'' is the t ...

'' Wawra, 1988 (Pseudunelidae) – marine # ''

Pseudunela espiritusanta ''Pseudunela espiritusanta'' is a species of sea slug, an acochlidian, a shell-less marine gastropod mollusk in the family Pseudunelidae. Its specific name is a reference to Espiritu Santo Island in Vanuatu, where it was found. This species, f ...

'' Neusser & Schrödl, 2009 (Pseudunelidae) – in brackish water # ''

Pseudunela marteli ''Pseudunela marteli'' is a species of sea slug, an acochlidian, a shell-less marine gastropod mollusk in the family Pseudunelidae. The specific name ''marteli'' is in honour of author's "big-hearted friend and colleague" biologist Martin “Mar ...

'' Neusser, Jörger & Schrödl, 2011 (Pseudunelidae) – marine # ''

Pseudunela viatoris ''Pseudunela viatoris'' is a species of sea slug, an acochlidian, a shell-less marine gastropod mollusk in the family Pseudunelidae. The specific name ''viatoris'' is after the Latin word “viator” (engl. pilgrim/voyager) according to its sup ...

'' Neusser, Jörger & Schrödl, 2011 (Pseudunelidae) – marineNeusser T. P., Jörger K. M. & Schrödl M. (2011). "Cryptic Species in Tropic Sands - Interactive 3D Anatomy, Molecular Phylogeny and Evolution of Meiofaunal Pseudunelidae (Gastropoda, Acochlidia)". '' PLoS ONE'' 6(8): e23313. . # '' Aiteng ater'' Swennen & Buatip, 2009 (Aitengidae) – marine (and brackish) # '' Aiteng marefugitus'' Kano, Neusser, Fukumori, Jörger & Schrödl, 2015 (Aitengidae) – marine # '' Aiteng mysticus'' Neusser, Fukuda, Jörger, Kano & Schrödl, 2011 (Aitengidae) – from Japan # '' Bathyhedyle boucheti'' Neusser, Jörger, Lodde-Bensch, Strong & Schrödl, 2016 (Bathyhedylidae) - marine # ''

Strubellia paradoxa ''Strubellia paradoxa'' is a species of freshwater slug, a shell-less freshwater gastropod,Strong E. E., Gargominy O., Ponder W. F. & Bouchet P. (2008). "Global Diversity of Gastropods (Gastropoda; Mollusca) in Freshwater". ''Hydrobiologia'' 595 ...

'' (Strubell, 1892) (Acochlidiidae) – freshwater # ''

Strubellia wawrai ''Strubellia paradoxa'' is a species of freshwater slug, a shell-less freshwater gastropod,Strong E. E., Gargominy O., Ponder W. F. & Bouchet P. (2008). "Global Diversity of Gastropods (Gastropoda; Mollusca) in Freshwater". ''Hydrobiologia'' 595 ...

'' Brenzinger, Neusser, Jörger & Schrödl, 2011 (Acochlidiidae) – freshwater # ''

Acochlidium amboinense ''Acochlidium amboinense'' is a species of freshwater gastropod, an aquatic gastropod mollusc within the family Acochlidiidae. References Acochlidiidae Gastropods described in 1892 {{Heterobranchia-stub ...

'' (Strubell, 1892) (Acochlidiidae) – freshwater # ''

Acochlidium bayerfehlmanni ''Acochlidium bayerfehlmanni'' is a species of freshwater gastropod, an aquatic gastropod mollusc within the family Acochlidiidae. The specific name ''bayerfehlmanni'' is in honour of Frederick Merkle Bayer and of Herman Adair Fehlmann, who mad ...

'' Wawra, 1980 (Acochlidiidae) – freshwater # '' Acochlidium fijiiensis'' Haynes & Kenchington, 1991Haynes A. & Kenchington W. (1991). "''Acochlidium fijiiensis'' sp. nov. (Gastropoda: Opisthobranchia: Acochlidiacea) from Fiji". ''The Veliger'' 34(2): 166–171. (Acochlidiidae) – freshwater # ''

Palliohedyle sutteri ''Palliohedyle sutteri'' is a species of gastropods belonging to the family Acochlidiidae Acochlidiidae are a taxonomic family of shell-less freshwater gastropods (one of them ''Palliohedyle weberi'' lives in brackish water),Schrödl M. & Neu ...

'' (Wawra, 1979) (Acochlidiidae) – freshwater # ''

Palliohedyle weberi ''Palliohedyle'' is a genus of gastropods belonging to the family Acochlidiidae. Species: *''Palliohedyle sutteri'' *''Palliohedyle weberi ''Palliohedyle'' is a genus of gastropods belonging to the family Acochlidiidae. Species: *''Palliohe ...

'' (Bergh, 1895) (Acochlidiidae) – in brackish waters # '' Tantulum elegans'' Rankin, 1979 (Tantulidae) – freshwater # ''

Asperspina brambelli ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (2010 ...

'' (Swedmark, 1968) (Asperspinidae) # ''

Asperspina loricata ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (2010 ...

'' (Swedmark, 1968) (Asperspinidae) # ''

Asperspina murmanica ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (2010 ...

'' (Kudinskaya & Minichev, 1978) (Asperspinidae) # ''

Asperspina rhopalotecta ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (2010 ...

'' Salvini-Plawen, 1973 (Asperspinidae) # ''

Asperspina riseri ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (2010 ...

'' (Morse, 1976) (Asperspinidae) # '' Microhedyle gerlachi'' Marcus & Marcus, 1959 - synonym: '' Parhedyle gerlachi'' (Ev. Marcus & Er. Marcus, 1959) (Microhedylidae) # '' Microhedyle glandulifera'' (Kowalevsky, 1901) (Microhedylidae) # '' Microhedyle nahantensis'' (Doe, 1974) (Microhedylidae) # '' Microhedyle remanei'' (Er. Marcus, 1953) (Microhedylidae) # '' Ganitus evelinae'' Marcus, 1953 (Microhedylidae s.l. / Ganitidae) # '' Paraganitus ellynnae'' Challis, 1968 (Microhedylidae s.l. / Ganitidae) # ''

Parhedyle cryptophthalma ''Parhedyle cryptophthalma'' is a species of sea slug, an acochlidian, a shell-less marine gastropod mollusk in the family Microhedylidae. Distribution This species occurs in the Mediterranean Sea The Mediterranean Sea is a sea connected ...

'' (Westheide & Wawra, 1974) (Microhedylidae) # ''

Parhedyle odhneri ''Parhedyle'' is a genus of gastropods belonging to the family Microhedylidae. The species of this genus are found in Europe. Species: *''Parhedyle cryptophthalma'' *'' Parhedyle odhneri'' *''Parhedyle tyrtowii ''Parhedyle'' is a genus of g ...

'' (Ev. Marcus & Er. Marcus, 1955) - synonym: '' Microhedyle odhneri'' (Ev. Marcus & Er. Marcus, 1955) (Microhedylidae) # ''

Parhedyle tyrtowii ''Parhedyle'' is a genus of gastropods belonging to the family Microhedylidae. The species of this genus are found in Europe. Species: *'' Parhedyle cryptophthalma'' *'' Parhedyle odhneri'' *''Parhedyle tyrtowii ''Parhedyle'' is a genus of ...

'' (Kowalevsky, 1900) (Microhedylidae) # '' Pontohedyle brasilensis'' (Rankin, 1979) (Microhedylidae) # ''

Pontohedyle joni ''Pontohedyle'' is a genus of sea slugs, acochlidians, shell-less marine gastropod mollusks in the family Microhedylidae. Sea slugs in this genus are highly simplified and uniform. Distribution The genus ''Pontohedyle'' shows a circumtropical di ...