Flabellinidae Bergh, 1889, restricted

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 : 39-40

Family Flabellinidae Bergh, 1889, restricted

Diagnosis.

Body commonly narrow. Notal edge discontinuous or fully reduced. Cerata in separate clusters, on elevations or distinct stalks. Rhinophores smooth, annulated or papillated. Anus mixed (pleuroproctic in higher acleioproctic position) or pleuroproctic under the reduced notal edge. Distinct oral glands present, commonly penetrate below anterior cerata. Radula formula 1.1.1. Rachidian teeth usually compressed by adjacent lateral denticles. Lateral teeth with attenuated process basally, usually denticulated, rarely smooth. Number and position of receptaculum seminis variable: two separate ones, or double proximal and single distal, or double distal one, in few cases proximal receptaculum not evident. Vas deferens usually long, with indistinct prostate. External permanent penial collar absent. Penis usually elongated conical, narrow, always internal unarmed.

Genera included.

Calmella Eliot, 1910, Carronella gen. n., Coryphellina O’Donoghue, 1929, Edmundsella gen. n., Flabellina Gray, 1833 in Griffith and Pidgeon, 1833-1834, Paraflabellina gen. n., Piseinotecus (?) Marcus, 1955.

Remarks.

The name Flabellinidae has been used for a long time to encompass all the diversity of aeolidaceans with a triseriate radula and without a clearly defined supplementary (or penial) gland in the male part of reproductive system. However, according to our present molecular phylogenetic analysis (Figs 1, 2), the former Flabellinidae form several distinct clades. Remarkably, some of them appear to be closely related to traditional Tergipedidae or Facelinidae thus making any notion that traditional Flabellinidae can be saved as a monophyletic unit highly unlikely.

Therefore, following the phylogenetic pattern discovered from the DNA analysis (Fig. 1) and consolidated morphological data (Fig. 2) we consistently utilise a differential approach, and propose several family level groups within traditional " Flabellinidae ". The super-cluster of the majority of traditional Flabellinidae holds a central position within this group and is apparently monophyletic (Fig. 2). It is, however, comprised of three clearly defined clades, which roughly correspond to the traditional genera Chlamylla , Coryphella , and Flabellina . However, a decision to maintain these phylogenetic superclusters just at generic levels will considerably obscure the complicated evolutionary patterns discovered from the molecular analysis (Fig. 1) which must be consistently reflected in a classification. Importantly, every large phylogenetic cluster has clear morphological trends. For example, the reinstated family Paracoryphellidae is characterised by the invariable presence of a wide body and continuous notal edge, elongated penis, and presence of complicated external penial collars or external permanent penis in two genera, and also invariably an uncompressed cusp of the rachidian teeth. The reinstated family Coryphellidae contains mostly taxa with a narrow body and discontinuous notal edge, but importantly there are several genera not directly related to other coryphellids (e.g., Borealia , Himatina , Gulenia , Itaxia , see above) that possess a continuous notal edge, which are all basal to various clades of narrow-bodied coryphellids. Internally most of the genera of the family Coryphellidae possess a non-compressed cusp of the rachidian teeth, short vas deferens, and broad penis always without an external penial collar. In turn, the considerably restricted family Flabellinidae s. str. includes taxa which usually have various ceratal elevations, up to highly ramified stalks in the genus Flabellina s. str. The family Flabellinidae in the restricted sense also includes such clear morphological trends as an almost invariably compressed cusp of the rachidian teeth, lateral teeth with attenuated bases, commonly large oral glands and usually a relatively long vas deferens and elongated penis (see below).

The minimum uncorrected p-distances of the mitochondrial barcode marker (COI) between the species of family Flabellinidae are given in Table 2. The minimum uncorrected p-distances between all genera range from 13.1 to 20.2%. The lowest distances occurred between Coryphellina rubrolineata and Edmundsella pedata (13.1%). Such considerable molecular divergence between taxa of the family Flabellinidae supports the reliability of the multi-genera approach consistently applied in this study.