Coryphellidae Bergh, 1889, reinstated

Korshunova, Tatiana, Martynov, Alexander, Bakken, Torkild, Evertsen, Jussi, Fletcher, Karin, Mudianta, I Wayan, Saito, Hiroshi, Lundin, Kennet, Michael Schroedl, & Picton, Bernard, 2017, Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda), ZooKeys 717, pp. 1-139 : 21-22

Family Coryphellidae Bergh, 1889, reinstated

Diagnosis.

Body wide to narrow. Notal edge reduced continuous, discontinuous, or fully reduced. Cerata not stalked, in continuous or discontinuous numerous rows. Rhinophores smooth, wrinkled, rarely annulated or perfoliated. Anus pleuroproctic under the reduced notal edge. Distinct oral glands commonly absent. Radula formula 1.1.1. Rachidian teeth usually with strong cusp, only rarely compressed by adjacent lateral denticles. Lateral teeth narrow or with attenuated process basally, always denticulated. Commonly both distal and proximal receptaculum seminis present. Vas deferens usually short, rarely long, with indistinct prostate. External permanent penial collar absent. Penis in many cases broad to disk-shaped, more rarely elongated conical, always internal, unarmed.

Genera included.

Borealia gen. n., Coryphella Gray, 1850, Fjordia gen. n., Gulenia gen. n., Himatina Thiele, 1931, Itaxia gen. n., Microchlamylla gen. n., Occidentella gen. n., Orientella gen. n.

Remarks.

The molecular analysis showed the presence of a well-supported (PP = 1, BS = 94) big clade (Figs 1, 2) which encompassed the majority of the traditional Coryphella (originally suggested by Gray 1850) including type species C. verrucosa , and also C. lineata , C. nobilis and C. gracilis . This clade is clearly distinct from the other traditional Flabellinidae as well as traditional basal Coryphellidae now placed in the separate family Paracoryphellidae (see above). However, even in the restricted sense Coryphella remains extremely heterogeneous by morphology of the notal ridge (continuous to discontinuous) and reproductive system anatomy (relatively long as in C. gracilis and C. amabilis , S-shaped in the type species C. verrucosa , or very short as in C. lineata or C. browni ; C. athadona instead possesses an aberrant penial gland distal part of the prostate). The penis usually appears as a wide lobe in many species but may also be narrow and conical as in C. gracilis and C. nobilis ). Thus, a further separation of more narrow genera within the reinstated family Coryphellidae is clearly necessary. The molecular analysis based on broad sampling of many Coryphellidae across both northern and southern hemispheres supports such a decision since it resulted in the formation of many well-supported smaller clades within the family Coryphellidae (Fig. 2). For example, the morphologically quite different C. athadona and C. trilineata stand apart and cluster more basally from the majority of the traditional Coryphella . Presence within the traditional genus Coryphella of wide bodied taxa like C. nobilis , C. trophina with continuous notal ridges, and the complete separateness (along with paraphyly) of the genus Flabellina implies that transformation of the continuous well-defined ancestral notal ridge into derived stalks or elevations has occurred several times independently within the family Flabellinidae . It is notable that wide bodied (new and resurrected) genera with a continuous notal edge, namely Borealia , Itaxia and Himatina , hold the most basal positions within various smaller clades of the family Coryphellidae (Fig. 2) suggesting that the common ancestor of all Coryphellidae was wide-bodied with a well-defined notal edge, as in the more basally placed members of the family Paracoryphellidae . The minimum uncorrected p-distances for the partial COI gene between the species of family Coryphellidae are given in Table 1. The minimum uncorrected p- distances between all genera range 10.1-18.3%. The lowest distances occurred between Himatina trophina and Fjordia chriskaugei (10.1%). Whereas the maximal uncorrected p-distances for the COI fragments between Fjordia browni and Fjordia lineata reach 6.4%, between Fjordia lineata and Fjordia chriskaugei sp. n. they reach 6.1%. Intra-genera variability reached significantly smaller values than variability between genera. The biggest distances occurred between Itaxia falklandica and other genera of family Coryphellidae (range 12.0-18.3%). Such considerable molecular divergences between taxa of the family Coryphellidae (Table 1) support the reliability of a multi-genera approach consistently applied in this study.