Nudibranchia Cuvier, 1817

Korshunova, Tatiana, Fletcher, Karin & Martynov, Alexander, 2025, The endless forms are the most differentiated-how taxonomic pseudo-optimization masked natural diversity and evolution: the nudibranch case, Zoological Journal of the Linnean Society 204 (4) : -

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https://doi.org/10.1093/zoolinnean/zlaf057

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scientific name

Nudibranchia Cuvier
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Order Nudibranchia Cuvier View in CoL in Blainville, 1814, restricted

Diagnosis: Notum primarily present, often reduced. Shell in adult state absent. Rhinophores primarily separated, secondarily united, initially rhinophores connected to broad oral veil that replaces anterior notum, often reduced, or oral tentacles formed. True gill absent, often various secondary structures (branched outgrowths, cerata, etc.) arranged latero-dorsally on both sides of the body. Anal opening initially remains in ventro-lateral position, secondarily may shift dorsally. Jaws entire, radula initially multiserial, with hooked teeth, often reduced to one tooth per row, central teeth usually present. Digestive gland initially entire, usually branched to varying degrees, in many taxa branches penetrate dorsal processes. Reproductive system usually considered to be diaulic, but triaulic also present.

Suborders included: (See Remarks below for details) suborder Arminacea Odhner, 1934 , restricted, reinstated; suborder Tritoniacea Lamarck, 1809 , reinstated; suborder Dendronotacea Odhner, 1934 , restricted, reinstated; suborder Janolacea Minichev and Starobogatov, 1979 , amended, reinstated; suborder Aeolidacea Odhner, 1934 , reinstated.

Remarks: To reinstate the suborder status for the Aeolidacea , first the higher order-level systematics of ‘nudibranchs’, which has an intricate history, needs to be clarified. Initially, the separate order Nudibranchia was for the first time introduced in the same work of Blainville (1814) on the same page, but under two different names—Polybranches (Blainville 1814: 177, not to be confused with the subsequent misapplication for sacoglossans), and Nudibranches (Cuvier inBlainville 1814: 177). The original diagnosis for Blainville’s order Polybranchia clearly reads ‘respiratory processes subdivided into numerous small branches’, and further, importantly, placed ‘at two sides of the whole body’ as ‘a main distinguishing character’. Simultaneously, for dorids Blainville (1814: 178) introduced the separate order Cyclobranches (not to be confused with the subsequent misapplication of the name ‘Cyclobranches’ for patellids and chitons by Cuvier 1817: 451). Dorids immediately differ from ‘Nudibranchia’ by the presence of the predominantly dorsal gill, modified into a circle, at least in part homological to the lateral gill of the order Pleurobranchida ( Wägele and Willan 2000) , by ontogenetic patterns (Martynov 2011, Martynov and Korshunova 2015, Martynov et al. 2022), and, regardless of its sister-position to Nudibranchia , forms a robustly supported, separate clade, according to the molecular phylogenetic analyses ( Korshunova et al. 2020a, Knutson 2021). Evidently, under the name Cyclobranches ( Cyclobranchia ), Blainville implied precisely the circular gill of dorids, whereas included the ‘addition’, onchidiids, possess different secondary dorsal respiratory structures. Unfortunately, the proposal by Blainville, which is strongly supported by modern multisource data, has been historically diminished under the sweeping name ‘Nudibranchia’ (Cuvier in Blainville 1814: 177, Cuvier 1817: 389), although the ordinal status for dorids has been persistently attempted to be resurrected under several different names ( Wägele and Willan 2000). Thus, despite the fundamental differences between Nudibranchia and Doridida , explicitly indicated at the ordinal ranks very early in the history of sea slug classification, currently dorids are considered just a ‘suborder’ of ‘Nudibranchia’ s.l., whereas Nudibranchia in the original sense was renamed significantly later as ‘Cladobranchia Willan and Morton, 1984 ’ ( Wägele and Willan 2000).

Importantly, in Blainville (1814: 177, our italics), it is unequivocally stated that ‘ Mr. de Blainville gives the fourth order the name Polybranches [ Polybranchia ], intending to indicate that the organs of respiration are subdivided into a fairly large number of small gills, but its principal characteristic is actually that these organs arranged in two rows, on each side of the animal’s body and completely exposed, what Mr. Cuvier designated under the name Nudibranches [ Nudibranchia ], which could even be preserved without inconvenience.…’, and on the same page it is unambiguously stated that ‘…the genus Doris Mr. Blainville places in particular order [which on the page 178 is designated as the order Cyclobranches ]’. Thus, regardless of the implied taxonomic content of Nudibranchia by Cuvier, Blainville immediately distinguished these two major body plans at the order level, not just as suborders or families. In a further work, Blainville (1816: 51–53) explicitly listed in the details for his order Polybranchia several core genera, including Glaucus, Tergipe s, Eolidia , Scyllaea , Tritonia , and Thetys , thus undoubtedly covering the major diversity of the Nudibranchia without dorids. Cuvier (1817: 389), instead, further reinforced the lumped classification by the unexplained complete omission of Blainville’s two ordinal system, and furthermore, by the incorrect usage of Blainville’s dorid’s order Cyclobranchia , for very different and distantly related patellids and chitons ( Cuvier 1817: 451). Therefore, the original diagnosis for Nudibranchia , with the initial explicit removal of the dorids (Blainville 1814: 177, not subsequent diagnosis byCuvier 1817: 389), almost ideally fits into the 170-year later concept of ‘Cladobranchia Willan and Morton, 1984 ’, which unambiguously implied the same diagnosis of the possession of numerous secondary respiratory processes on both sides of the body, either branched or not, but not a true dorid’s gill. Wägele and Willan (2000: 89) also clearly indicated that Nudibranchia has been renamed to Cladobranchia by Willan and Morton (1984) for the traditional suborders Dendronotacea , Arminacea , and Aeolidacea , exactly to accommodate the two-order system by Minichev (1970: 176), who explicitly used order Anthobranchia for dorids, and order Nudibranchia for traditional aeolidaceans, dendronotaceans, and arminaceans: ‘Minichev called his clades Anthobranchia (for the dorids) and Nudibranchia ( renamed Cladobranchia by Willan and Morton 1984) for the aeolids, arminids and dendronotaceans’.

Given the enormity of hidden diversity at a very fine scale ( Martynov and Korshunova 2022, Korshunova and Martynov 2024) worldwide that still awaits description in all organismal group, it is especially important to accurately separate drastically different patterns of major organizations at a higher scale, such as Nudibranchia and Doridida . This separation was performed at the initial ‘joined’ description of the orders Nudibranchia (Polybranchia) and Doridida ( Cyclobranchia ) in Blainville (1814), and there are no historical, morphological, or phylogenetic reasons to dismiss that insightful initial designation. Herein, therefore, the order Nudibranchia is restricted (= Cladobranchia Willan and Morton, 1984) to the taxa without a true gill, thus restoring the original designation by Blainville (1814) without dorids. Respectively, the full ordinal status for the order Doridida is reinstated. Pelseneer (1894) was probably the first to clearly apply the name with the stem ‘Dorid-’ as a taxon above the family group (as a taxon ‘Doridiens’, yet within ‘Nudibranches’ s.l.). Therefore the authorship of the order Doridida , ordinal status restored, is assigned to Pelseneer (1894). For morphological diagnoses, and a list of included families for the order Doridida , see Martynov (2011), Korshunova et al. 2020a, and Martynov and Korshunova (2025). According to ontogenetic data (Martynov 2011, Martynov et al. 2022), the order Nudibranchia is well differentiated from the order Doridida initially by separated rhinophores, which in the course of subsequent evolution may be secondarily united [for a comparison of patterns of the families Doridoxidae and Arminidae , see details in Korshunova and Martynov (2020)]. We have consistently applied the two-order system of nudibranchs, order Nudibranchia and order Doridida , respectively, throughout a series of our works (e.g. Martynov and Korshunova 2011, 2012, Martynov et al. 2022), including molecular phylogenetic analyses, Korshunova et al. 2017a, 2020a).

The reinstated, monophyletic suborder Aeolidacea ( Figs 1, 2) belongs to the restricted order Nudibranchia , along with the traditional suborders Arminacea Odhner, 1934 and Dendronotacea Odhner, 1934 , both are definitely heterogeneous and paraphyletic ( Goodheart et al. 2018, Korshunova and Martynov 2020, Karmeinski et al. 2021, Knutson 2021). Therefore, to further properly delineate the suborder Aeolidacea , the following suborders need to be restricted and reinstated within the proper Nudibranchia :

Suborder Arminacea Odhner, 1934 , restricted, reinstated, with the main diagnosis being the presence of a well-defined notum, moderately tuberculated or striated, without distinct or branched appendages, secondary branchial lamellae may be present under the notum, rhinophores and oral veil connected in various degrees, rhinophores initially separated, secondarily united, digestive gland externally unbranched to moderately branched, and radula multiserial. Includes the superfamily Doridoxoidea Bergh, 1899 View in CoL with the families Doridoxidae Bergh, 1899 View in CoL , Heterodorididae Verrill and Emerton, 1882 View in CoL , Doridomorphidae Er.Marcus and Ev. Marcus, 1960 View in CoL , and the superfamily Arminoidea Iredale and O’Donoghue, 1923 View in CoL , with the family Arminidae Iredale and O’Donoghue, 1923 View in CoL [see molecular phylogenetic analysis in Korshunova and Martynov (2020)].

Suborder Tritoniacea Lamarck, 1809 sensu Minichev and Starobogatov, 1979 , reinstated. Lamarck’s original (1809) order-level name ‘Tritoniens’, despite being based on the stem-genus name ‘Tritonia’, in its initial taxonomic composition ( Lamarck 1809) was equal to both orders Nudibranchia View in CoL and Doridida and, therefore, unsuitable for the narrow diagnosis of the suborder Tritoniacea . Minichev and Starobogatov (1979) instead proposed the amended name ‘Tritoniina’, as part of the reformation of traditional ‘Dendronotacea’ in the rank of a separate suborder. The main diagnosis of Tritoniacea is the well-defined, broad, to reduced notum with commonly a various number of branched appendages (secondary gills) dorso-laterally on both sides of the body, rhinophores and oral veil originally connected in various degrees, but the connection is less evident in a majority of taxa, rhinophores initially separate, digestive gland externally not considerably branched, rather compact and does not penetrate into the dorsal appendages, radula multiserial to oligoserial. For details on the included superfamily Tritonioidea Lamarck, 1809 View in CoL , with a single family Tritoniidae Lamarck, 1809 View in CoL , see the molecular phylogenetic analysis in Korshunova and Martynov (2020).

Suborder Dendronotacea Odhner, 1934 , reinstated, restricted to exclude Tritoniidae View in CoL , with the main diagnosis being the possession of a considerably reduced to completely absent notum with commonly various branched appendages, rhinophores and oral veil not evidently connected in a majority of taxa, the initial separation of rhinophores is also less evident, digestive gland externally usually considerably branched, and partly penetrates into the dorsal appendages, but definite aeolidacean-like cnidosacs are never formed, radula multiserial to more commonly oligoserial. Included is the superfamily Dendronotoidea Allman, 1845 View in CoL with the families Bornellidae Bergh, 1874 View in CoL , Dendronotidae Allman, 1845 View in CoL , Dotidae Gray, 1853 View in CoL , Hancockiidae MacFarland, 1923 View in CoL , Lomanotidae Bergh, 1890 View in CoL , Phylliroidae Menke, 1830 View in CoL , Scyllaeidae Alder and Hancock, 1855 View in CoL , and Tethydidae Rafinesque, 1815 View in CoL ; more superfamilies need to be recognized.

Suborder Janolacea Minichev and Starobogatov, 1979 , amended, reinstated. The restoration and separation of this suborder is necessary to repair the paraphyletic traditional arminaceans (e.g. Wägele and Willan 2000, Goodheart et al. 2018, Korshunova and Martynov 2020)— because there is a group of arminacean-like nudibranchs of the superfamily Proctonotoidea Gray, 1853 View in CoL (the family list is below), which are only distantly related to the true Arminacea in a restricted sense (e.g. including Arminidae View in CoL and Doridoxidae View in CoL , see references above). The main diagnosis for the suborder Janolacea ranges from a well-defined notum without dorsal appendages to a completely reduced notum with dorsal unbranched appendages, rhinophores and oral veil are evidently connected only in two families, but not in a majority of taxa, digestive gland from not considerably branched externally to strongly branched, and commonly may penetrate into the dorsal appendages, but definite cnidosacs are never formed, radula multiserial to triserial. Includes the superfamily Proctonotoidea Gray, 1853 View in CoL , with the families Curnonidae d’Udekem d’Acoz, 2017 View in CoL , Lemindidae Griffiths, 1985 View in CoL , Dironidae Eliot, 1910 View in CoL , Madrellidae Preston, 1911 View in CoL , Proctonotidae Gray, 1853 View in CoL , Janolidae Pruvot-Fol, 1933 View in CoL , and possibly also Goniaeolidiidae Odhner, 1907; more superfamilies need to be recognized. The genus Trivettea Bertsch, 2014 View in CoL and the family Heroidae Gray, 1857 View in CoL remained incertae sedis regarding suborder placement within Nudibranchia View in CoL ; the genus Bathydevius Robison and Haddock, 2024 View in CoL remains incertae sedis regarding ordinal placement.

ThesuborderJanolaceaisanimportantevolutionaryprecursor for the further formation of the definite cnidosac-bearing suborder Aeolidacea , since it represents its sister-group according to the molecular phylogenetic analyses ( Goodheart et al. 2018, Karmeinski et al. 2021, Knutson 2021, present study, Figs 1, 2), and, therefore, the refined diagnosis for the order Nudibranchia View in CoL proper and discussion of its suborders’ composition presented above is immediately relevant for the major theme of the present study of the high morphological diversity and the numerous distinct molecular lineages, revealed in the suborder Aeolidacea ( Figs 1, 2).

Suborder Aeolidacea Odhner, 1934 , reinstated

( Figs 1, 2)

Diagnosis: Body bears dorsal cerata (papillae) of various lengths, number and pattern of placement, but basically in two sets of commonly numerous, partly crowded or, rarely, few in number, separately placed cerata dorso-laterally across almost the entire body length. The initial connection of separated rhinophores with broad oral veil almost completely reduced; rhinophores in adult state commonly closely placed. In an absolute majority of superfamilies, a fully functional single cnidosac (a storage area for nematocysts, which are stinging cells ingested for self-defence from cnidarian prey) is present in the apical part of the cerata. Very rarely the cnidosac is secondarily reduced. Branched appendages or gill-like structures are absent. Digestive gland in all superfamilies is branched in various degrees and patterns, including regular, simple rows. Anal opening may found on the right lateral side of the body (pleuroproctic), in between the anterior and posterior digestive gland branches on the right side of the body (acleioproctic), or between the branches of the posterior digestive gland on the right side of the body (cleioproctic), or very rarely placed toward the posterior extreme of the body. There are also some mixed states of anal opening placement. Jaws are found as a pair of whole, strong plates placed inside of each lateral side of the pharynx. Masticatory edges of the jaws bear various denticle-like structures in various patterns, or, more rarely, smooth. Radula formula falls into three main patterns: oligoserial (commonly more than one and less than 10 longitudinal rows of lateral teeth flank central teeth from each side), triserial (one longitudinal row of lateral teeth on each side of central teeth), and uniserial (lateral teeth completely reduced). Oligoserial is a very rare pattern within Aeolidacea , the majority of superfamilies possess either triserial or uniseral radula. Central (= rachidian) teeth usually with central cusp and various numbers and shapes of lateral denticles. In some families central teeth become pectinate, where the central cusp is reduced and may become almost indistinguishable. In a unique case, uniserial radular teeth are fused together in a continuous ribbon-like pattern. So far, there are no known cases within Aeolidacea where the radula is completely reduced. Reproductive system described as commonly diaulic, but there are patterns in various superfamilies that can be similar to a triaulic condition. Both distal and proximal seminal receptaculums, or only a single, distal or proximal receptaculum, present. If a single receptaculum is present, it is more commonly a distal receptaculum. Prostate rarely elaborate, evidently granulated, more commonly forms a prostatic vas deferens, but vas deferens and prostate itself in many cases remain relatively distinct. Copulative apparatus commonly includes entire, contractable, but usually non-evertable, penis of various shapes and lengths. Extremely rarely (in at least one taxon of the family Notaeolidiidae and in the genus Paracoryphella of the family Paracoryphellidae ) the penis is directly attached to the external body wall. In different families, the penis may bear various hard structures, such as single or multiple stylets, or soft structures, such as warts, tubercles, or folds. Copulative apparatus may also include various glands, which form, in one particular superfamily, a special supplementary gland inserted to the vas deferens or penis, whereas in others form different accessory glands.

Remarks: As a main result of the present study what follows is an updated system of the aeolidacean superfamilies and a Synopsis of all the aeolidacean families so far known, derived from the molecular phylogenetic analysis, which included all the families so far known, and two newly described aeolidacean families ( Figs 1, 2). In a tight connection with the reliable comparison of the two new families from different aeolidacean lineages ( Fig. 2) with all other aeolidacean family-level taxa, it needs to be specially highlighted that the current system of superfamilies of aeolidacean nudibranchs employed in the World Register of Marine Species (WoRMS 2024) is inconsistent with existing morphological and molecular data (see Results, and Synopsis below, including diagnoses of the new families; Figs 1, 2; Tables 1, 2). One of the major inconsistencies is that a number of families that belong to respective phylogenetically clearly distinct clades and correspond to morphological aeolidacean supergroups, such as Fionoidea , Flabellinoidea , and Aeolidioidea ( Fig. 2), currently are chaotically scattered among the only two currently recognized superfamilies, Aeolidioidea and Fionoidea . For example, the core flabellinoideans of the families Coryphellidae and Paracoryphellidae (see Results andFigs 1, 2), for some reason are currently placed in WoRMS (2024) within a completely different morphological and molecular superfamily Fionoidea . Whereas, simultaneously, the actual Flabellinidae are definitely closer to the above-mentioned Coryphellidae and Paracoryphellidae than to any aeolidioidean families ( Fig. 2), but for some equally unexplained reason they are placed instead into a very different molecular and morphological superfamily Aeolidioidea (WoRMS 2024) .

To counter this synonymization, over the past seven years we have presented several comprehensive aeolidacean phylogenies, which included all previously known and newly described families ( Korshunova et al. 2017a, 2019b, Martynov et al. 2020, present study; Figs 1, 2). Therefore, we now have a sufficient basis for a superfamilies-based classification of Aeolidacea . In those previous, and these present, phylogenies, no representatives of the core of the main superfamilies Flabellinoidea , Aeolidioidea , and Fionoidea have been mixed with each other and all three major supergroups are monophyletic with high support ( Figs 1, 2). The genus Edmundsella , which previously has shown some paraphyly with regard to other families ( Goodheart et al. 2018), is invariably placed as an integral part of the monophyletic family Flabellinidae with the inclusion of the family stem-genus Flabellina ( Korshunova et al. 2017a, present study; Figs 1, 2) and consistently nested within other flabellinoids, but not with any other Fionoidea ( Figs 1, 2). In turn, Flabellinopsidae are invariably placed as sister to the majority of core Flabellinoidea , but never with the family Notaeolidiidae ( Korshunova et al. 2017a, present study; Figs 1, 2).

Therefore, the load of accumulated inconsistencies in the superfamily-based classification of the suborder Aeolidacea is currently so high that while we have separated two new taxa at the family-level (see below) in the present study, further progress in aeolidacean nudibranch phylogeny and classification is impossible without proper resolution of the above-mentioned serious objective contradiction in the superfamily-based classification of aeolidacean nudibranchs. Thus, before further comparison of the Hantazuidae fam. nov. and Chudidae fam. nov. (which are definitely distinctly different from any aeolidacean families—see diagnoses and descriptions in the Synopsis below; Figs 1, 2; Tables 1, 2) can be presented, we need to clarify the superfamily system of the suborder Aeolidacea . Fortunately, separation of the superfamilies is a nomenclaturally relatively easy action because according to ICZN (1999, article 36), and to the principle of coordination, a taxon of any rank in the family group, including superfamily, ‘is deemed to have been simultaneously established for nominal taxa at all other ranks in the family group’, with the same genus-derived stem family-group name and, importantly, the same authorship. Thus, using the accumulated comprehensive morphological and phylogenetic data on aeolidacean nudibranchs, we may now refine the aeolidacean superfamily system.

First, we separate and consider valid three major aeolidacean superfamilies, all of them having been previously supported for a sufficiently long time ( Bouchet et al. 2005, 2017; even with considerable reservations for the position of several families, see below) and in all of them, consistent morphological data align with evidently distinct phylogenetic clades ( Korshunova et al. 2017a, present study; Fig. 2): Flabellinoidea Bergh, 1889 , Aeolidioidea Gray, 1827 , and Fionoidea Gray, 1857 . The triserial superfamily Flabellinoidea Bergh, 1889 , reinstated, contains exclusively triserial families without a special supplementary gland in the male part of the hermaphroditic reproductive system (with the exception of a partly similar accessory gland in the coryphellid genus Occidenthella , but clearly independently evolved from fionoideans and aeolidioideans, see below)— Coryphellidae , Paracoryphellidae , and Flabellinidae . In turn, the uniserial superfamily Aeolidioidea Gray, 1827 contains a majority of the exclusively uniserial families without a special supplementary gland (some taxa with additional glandular formations associated with the copulative apparatus, independently evolved from fionoids)— Aeolidiidae , Myrrhinidae , Facelinidae , Favorinidae , Glaucidae , Babakinidae , and Pleurolidiidae . The triserial family Chudidae fam. nov., discovered through our present work, shows some relation to Aeolidioidea , but also aligns as a sister-taxon to several other Aeolidacean superfamilies ( Figs 1, 2), and thus cannot be unambiguously placed into any of the known or aeolidacean superfamilies ( Fig. 2; see detailed discussion below) established here; therefore, is placed in a separate superfamily Chudoidea superfam. nov. ( Figs 1, 2). Finally, the third largest aeolidacean superfamily, the predominantly uniserial superfamily Fionoidea Gray, 1857 contains a majority of the exclusively uniserial families with a special supplementary gland in the copulative apparatus (inserted more commonly into the penis or, more rarely, into the vas deferens)— Abronicidae , Murmaniidae , Xenocratenidae , Cuthonellidae , Calmidae , Cuthonidae , Tergipedidae , and Trinchesiidae . Paradoxically, within Fionoidea there is only a single family without a special supplementary gland and, notably, with a uniserial radula— the family Fionidae (the superfamily stem-genus Fiona bearing its name), but only a single triserial family, Eubranchidae ( Figs 1, 2).

However, apart from these three major aeolidacean superfamilies, there are several family-level taxa that cannot be included in any of these three major supergroups according to morphological and molecular data ( Figs 1, 2). The classificatory placement of these families according to their current superfamily position in WoRMS (2024) is also highly inconsistent. For example, two of the most basally placed aeolidacean triserial families, Apataidae and Samlidae —with disparate ceratal placement morphology and differing details of their reproductive systems—for some inexplicable reason are placed within the predominantly uniserial Fionoidea whose phylogenetic position is obviously very distant to Apataidae and Samlidae ( Figs 1, 2). The same is true for the triserial Cumanotidae , whose phylogenetic position, together with their paedomorphic sister-family Pseudovermidae ( Martynov et al. 2020) , do not show a definite relationship to any main aeolidacean superfamily or other family ( Fig. 2) according to all available analyses ( Martynov et al. 2020, present study; Fig. 1), but for some equally inexplicable reason are currently placed within the predominantly uniserial Fionoidea , which are obviously not directly related to the superfamily Cumanotidae . Furthermore, the triserial family Flabellinopsidae , together with the robustly morphologically and molecular confirmed ( Fig. 2) uniserial family Hantazuidae fam. nov. ( Fig. 2, see below), align as sister to the superfamily, Flabellinoidea , but without significant support ( Fig. 1).

Externally both the triserial Flabellinopsidae and the uniserial Hantazuidae fam. nov. are partly similar in the possession of a flap-like—rather than only discontinuous—notal edge or stalk-like ceratal peduncles of Flabellinoidea . But partly similar flaps may occur in core species of the otherwise distantly related ( Figs 1, 2) Notaeolidiidae ( Wägele 1990) family with an oligoserial radula. That external feature may not indicate a close relationship, but instead may have very ancient evolutionary roots for Aeolidacea , so that feature must be considered in the Aeolidacea superfamily classification. Additionally, the family Flabellinopsidae obviously shows a more distantly-related position compared to the core Flabellinoidea family, Flabellinidae , according to phylogenomic analysis (e.g. Karmeinski et al. 2021), and this provides additional justification of the more significant separation between core Flabellinoidea ( Paracoryphellidae , Flabellinidae , and Coryphellidae ) species and Flabellinopsidae . Therefore, taking into consideration the molecularly robust support between the triserial Flabellinopsidae and the uniserial Hantazuidae fam. nov. ( Figs 1, 2), the morphological disparity between Flabellinopsidae and Hantazuidae fam. nov. on the one hand, and the core triserial families Paracoryphellidae , Flabellinidae , and Coryphellidae (superfamily Flabellinoidea ) on the other hand, we have established the separate superfamily Flabellinopsoidea Korshunova et al., 2017 for the families Flabellinopsidae and Hantazuidae fam. nov. ( Fig. 1).

Ultimately, one of the most basal aeolidacean families, the family Notaeolidiidae (which aligns as sister to the family Samlidae , and together with Apataidae is sister to all other Aeolidacean families; Fig. 2), has the pattern of an oligoserial radula with more than one and less than 10 regular longitudinal rows of lateral teeth per each side, which is unknown in any other aeolidaceanfamily (seeTables 1,2). Nevertheless, Notaeolidiidae are currently placed in the drastically morphologically different, exclusively uniserial superfamily Aeolidioidea in WoRMS (2024). Considering all these obvious morphological and molecular inconsistencies, along with the above-outlined three major aeolidacean superfamilies, we recognize the following ‘lesser’ aeolidacean superfamilies: Notaeolidioidea Eliot, 1910 , Samloidea Korshunova et al., 2017 , Apataoidea Korshunova et al., 2017 , Unidentioidea Millen and Hermosillo, 2012 , Cumanotoidea Odhner, 1907 (apart from Cumanotidae also to include its paedomorphic close relatives Pseudovermidae , see: Martynov et al. 2020), and Flabellinopsoidea Korshunova et al., 2017 . The position of two smaller families with long-discussed uncertain positions such as Embletoniidae (Karmienski et al. 2021) and ‘Piseinotecidae’ ( Korshunova et al. 2017a), plus a few more uncertain taxa, are considered further in the present study (see Synopsis of all aeolidacean superfamilies and families below).

The separation of several ‘lesser’ superfamilies within Aeolidacea is not pursued to perform classic ‘classificatory division’, but clearly aims to maximally reflect the extremely complex, genuine evolutionary patterns within Aeolidacea ( Fig. 1), uncovered in all the performed analyses up to this point. Nearly all families are traditionally assessed as having strict distinct correspondence to particular family-level taxa features, such as patterns of the notal edge, position of the anus, a triserial or uniserial radula (e.g. Odhner 1934, Odhner in Franc 1968), and other characters that are distributed over family-level aeolidacean groups in a highly intricate, sometimes counter-intuitive pattern, forming an evolutionary-fuelled morphological and molecular immensely complicated picture ( Figs 1, 2). This complexity must be correspondingly reflected in the respective family- and superfamily-based revised Aeolidacean taxonomy. The family Embletoniidae Pruvot-Fol, 1954 shows a somewhat unsettled phylogenetic relationship to Aeolidacea (see: Martynov et al. 2020, Karmeinski et al. 2021) and is included in the present Synopsis as a separate superfamily addition, after all other aeolidacean superfamilies.

The updated Synopsis with the diagnoses of all of the abovediscussed valid aeolidacean superfamilies and families of the suborder Aeolidacea is, therefore, presented below and throughout the text. Further data may potentially correct some aspects of this classification of superfamilies, but according to the currently available extensive morphological data and robustly supported numerous aeolidacean phylogenetic superfamily clades ( Fig. 1), this classification scheme has a reliable evolutionary basis. In the future, more detailed genomic data may add further details to some of these clades and respective groups, but it is unlikely that it will change the major patterns of aeolidacean phylogeny. For example, the later phylogenomic study of Karmeinski et al. (2021) largely confirmed the major aeolidacean family-level clades originally revealed in Korshunova et al. (2017a).

Superfamilies included: Notaeolidioidea Eliot, 1910 , reinstated; Samloidea Korshunova et al., 2017 , herein established; Apataoidea Korshunova et al., 2017 , herein established; Unidentioidea Millen and Hermosillo, 2012 , herein established; Fionoidea Gray, 1857 , restricted; Cumanotoidea Odhner, 1907 , herein established; Chudoidea superfam. nov.; Aeolidioidea Gray, 1827 , restricted; Flabellinopsoidea Korshunova et al., 2017 , herein established; Flabellinoidea Bergh, 1889 , reinstated.

Synopsis of the suborder Aeolidacea

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

Order

Nudibranchia

Loc

Nudibranchia Cuvier

Korshunova, Tatiana, Fletcher, Karin & Martynov, Alexander 2025
2025
Loc

Bathydevius

Robison and Haddock 2024
2024
Loc

Curnonidae d’Udekem d’Acoz, 2017

d'Udekem d'Acoz 2017
2017
Loc

Trivettea

Bertsch 2014
2014
Loc

Lemindidae

Griffiths 1985
1985
Loc

Tritoniacea

Lamarck, 1809 sensu Minichev and Starobogatov 1979
1979
Loc

Tritoniacea

Lamarck, 1809 sensu Minichev and Starobogatov 1979
1979
Loc

Tritoniacea

Lamarck, 1809 sensu Minichev and Starobogatov 1979
1979
Loc

Janolacea

Minichev and Starobogatov 1979
1979
Loc

Janolacea

Minichev and Starobogatov 1979
1979
Loc

Doridomorphidae Er.Marcus and Ev. Marcus, 1960

Er. Marcus and Ev. Marcus 1960
1960
Loc

Arminacea

Odhner 1934
1934
Loc

Dendronotacea

Odhner 1934
1934
Loc

Arminacea

Odhner 1934
1934
Loc

Aeolidacea

Odhner 1934
1934
Loc

Aeolidacea

Odhner 1934
1934
Loc

Aeolidacea

Odhner 1934
1934
Loc

Janolidae

Pruvot-Fol 1933
1933
Loc

Arminoidea Iredale and O’Donoghue, 1923

Iredale and O'Donoghue 1923
1923
Loc

Arminidae Iredale and O’Donoghue, 1923

Iredale and O'Donoghue 1923
1923
Loc

Hancockiidae

MacFarland 1923
1923
Loc

Arminidae

Iredale and O'Donoghue 1923
1923
Loc

Madrellidae

Preston 1911
1911
Loc

Dironidae

Eliot 1910
1910
Loc

Doridoxoidea

Bergh 1899
1899
Loc

Doridoxidae

Bergh 1899
1899
Loc

Doridoxidae

Bergh 1899
1899
Loc

Lomanotidae

Bergh 1890
1890
Loc

Heterodorididae

Verrill and Emerton 1882
1882
Loc

Bornellidae

Bergh 1874
1874
Loc

Heroidae

Gray 1857
1857
Loc

Scyllaeidae

Alder and Hancock 1855
1855
Loc

Dotidae

Gray 1853
1853
Loc

Proctonotoidea

Gray 1853
1853
Loc

Proctonotoidea

Gray 1853
1853
Loc

Proctonotidae

Gray 1853
1853
Loc

Dendronotoidea

Allman 1845
1845
Loc

Dendronotidae

Allman 1845
1845
Loc

Phylliroidae

Menke 1830
1830
Loc

Tethydidae

Rafinesque 1815
1815
Loc

Tritonioidea

Lamarck 1809
1809
Loc

Tritoniidae

Lamarck 1809
1809
Loc

Tritoniidae

Lamarck 1809
1809
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