Aeolidiidae Gray, 1827

Family Aeolidiidae Gray, 1827 View in CoL

( Figs 1, 2; Table 4)

Gray 1827: pl. 3, figs 16–19.

Korshunova et al. 2017a: supplementary materials.

Diagnosis: Body broad to narrow. Notal edge completely reduced in majority of genera. Ceratal rows simple or arched, numerous non-elevated cerata per row. Rhinophores smooth, perfoliate, or papillate. Anus commonly cleioproctic, rarely pleuroproctic. Masticatory edges of jaws commonly smooth, but can also be moderately denticulated with single row of denticles. Radula formula 0.1.0. Central teeth arc-shaped, pectinate. Commonly proximal receptaculum seminis. Vas deferens moderately long to very long, prostate indistinct to moderately distinct. Accessory gland absent. Massive external permanent penial collar absent. Penis internal, narrow or broad, unarmed.

Genera included: Aeolidia Cuvier, 1798 , Aeolidiella Bergh, 1867 , Aeolidiopsis Pruvot-Fol, 1956 , Anteaeolidiella M. C. Miller, 2001 , Baeolidia Bergh,1888 , Berghia Trinchese,1877 , Bulbaeolidia Carmona, Pola et al., 2013 , Cerberilla Bergh, 1873 , Limenandra Haefelfinger and Stamm,1958 , Spurilla Bergh,1864 ,and Zeusia Korshunova et al.,2017 .

Remarks: One of the two oldest families within the suborder Aeolidacea , Aeolidiidae Gray, 1827 at the diagnostic level is well characterized by the presence of a cleioproctic anus in combination with broad, arc-shaped, pectinate radular teeth, but the deep-sea genus Zeusia Korshunova et al., 2017 , which evolutionarily is sister to the type genus of the family, Aeolidia , was proved as having a well-defined pleuroproctic anus ( Korshunova et al. 2017d). This fact that arc-shaped, pectinate radular teeth occur not only within the familiesFacelinidae(genus Burnaia Miller,2001 ) andPleurolidiidae, which are related to Aeolidiidae , but also within the very distantly related families Xenocratenidae and Trinchesiidae (genus Trinchesia Ihering, 1879 in narrow sense, see above), and understanding that pleuroproctic anus is an ancestral feature, in some form preserved at least in a few genera in a majority of the Aeolidacean superfamilies and families (e.g. even within the superfamily Fionoidea with a predominantly acleioproctic anus, there is a family Murmaniidae , in which, as a rarest exception, the pleuroproctic anus has been documented; Martynov 2006; Tables 3, 4), an overlumping approach has the potential to dismantle the entire family-level taxonomic structure within the suborder Aeolidacea , and place every species into a single family Aeolidiidae Gray, 1827 , or Glaucidae Gray, 1827 . Therefore, to prevent this, fine-scale morphological differentiation in combination with molecular data (Synopsis; Figs 1, 2; Tables 3, 4) must be applied regardless of whether the outcome results in species that are ‘easily characterized and recognized by the general public’ or not. To say that one must lump species into a single genus (e.g. Kim et al. 2024) so that it will be easier to identify nudibranchs in the field truly hinders the quest for knowledge that is the purpose of public scientific inquiry.

A particular case, related to the family Aeolidiidae , needs to be specially addressed. A family, Magallanidae , has been described recently by Ortea and Moro (2020) in an unusual manner. First, in the same paper, a new species, Aeolidiopsis elcanoi ( Ortea and Moro 2020: 16–24) , was described within an old genus, Aeolidiopsis , and the new species initially was placed unambiguously in the family Aeolidiidae ( Ortea and Moro 2020: 16) . However, at the end of the description of the new species Aeolidiopsis elcanoi ( Ortea and Moro 2020: 24) , it was assigned to a new genus Magallanes and a new family Magallanidae , very unusual for common taxonomic works; thus, its taxonomic position was presented in the same paper two times using two different sets of families and genera ( Ortea and Moro 2020: 24). Aeolidiopsis / Magallanes elcanoi possesses broad, arc-shaped, pectinated central teeth, a reproductive system with a relatively long vas deferens without a supplementary gland, and rather flattened cerata. All these characters are consistent with the current family Aeolidiidae , even taking into consideration our major principle of fine-scale taxonomy as consistently employed in the present study. Molecular data are not available for this taxon, although according to morphological data the genus Magallanes and the family Magallanidae are probably a part of the intrageneric diversity of the family Aeolidiidae (and, therefore, Magallanidae are not listed separately in the synopsis and Tables 3, 4), we refrain from its synonymy with Aeolidiidae , because with more data, Magallanidae may potentially contribute to a further fine-scale differentiation within Aeolidiidae , which is still partly heterogeneous and contains morphologically considerably different taxa.

Superfamily Flabellinopsoidea Korshunova et al., 2017 , herein established

( Figs 1, 2; Tables 1–3)

Diagnosis: Aeolidacean superfamily with triserial and uniserial radula.Body relatively wide to narrow.Notal edge discontinuous. Cerata on broad flap-like extensions, numerous per row. Ceratal rows branched. Rhinophores perfoliate, granulated to smooth. Anus pleuroproctic. Anterior foot corners present. Elaborate oral glands absent or present. Masticatory edges of jaws bear several rows of compound, sharpened or tubercle-like denticles. Central teeth usually with cusp compressed by adjacent lateral denticles. Lateral teeth narrow or with attenuated process basally, denticulated, smooth, or completely absent. Distal receptaculum seminis or proximal receptaculum also present. Clasping organ in female part of reproductive system absent. Vas deferens long, with distinct or indistinct prostate. Supplementary and accessory glands absent. Massive external permanent penial collar absent. Penis internal, unarmed or armed with stylet.

Families included: Flabellinopsidae Korshunova et al., 2017 and Hantazuidae fam. nov..

Remarks: The families Flabellinopsidae Korshunova et al., 2017 and Hantazuidae fam. nov., although internally completely disparate regarding such key family-level aeolidacean characters as the presence of a triserial or uniserial radula, as well as the absence or presence of a distinct hollow cuticular penial stylet (see Synopsis below), robustly align as sister to each other according to molecular phylogenetic analysis ( Figs 1, 2), and in turn are sister to the families Paracoryphellidae , Flabellinidae , and Coryphellidae , however, with lower support ( Figs 1, 2). Although previously the family Flabellinopsidae was also placed as sister to Paracoryphellidae , Flabellinidae , and Coryphellidae ( Korshunova et al. 2017a) , in some other analyses it is more distantly related to Flabellinidae ( Karmeinski et al. 2021) , or even as sister to Notaeolidiidae ( Goodheart et al. 2018) , which definitely possess a very different, ancestral oligoserial radula. Despite that, in our phylogenies with a maximally possible (at that time) broad taxon sampling ( Korshunova et al. 2017a), Flabellinopsidae invariably aligned as sister to Paracoryphellidae , Flabellinidae , and Coryphellidae . The previous results ( Goodheart et al. 2018, Karmeinski et al. 2021), and relatively low support in the present study ( Figs 1, 2), justified the separation of Flabellinopsidae Korshunova et al., 2017 and Hantazuidae fam. nov. into a separate superfamily Flabellinopsoidea Korshunova et al., 2017 , established herein (see Synopsis below; Figs 1, 2; Tables 1–4). In further support of this, despite that Flabellinopsidae Korshunova et al., 2017 and Hantazuidae fam. nov. internally are drastically different to a maximal degree, externally they show some similarity in the presence of flap-like, notal-derived ceratal bases ( MacFarland 1966, present study, see Synopsis below) instead of merely discontinuous notal edge or stalk-like ceratal bases as in the superfamily Flabellinoidea ( Korshunova et al. 2017a) , which thus morphologically justifies the separation of the superfamily Flabellinopsoidea ( Figs 1, 2).