Apataidae Korshunova et al. , 2017

Family Apataidae Korshunova et al., 2017 View in CoL

( Figs 1, 2; Table 4)

‘Genus Flabellina sensu latissimo ’ Gosliner and Griffiths 1981: 105 , 109–15.

Family Apataidae Korshunova et al. 2017a: 63 View in CoL .

Diagnosis: Body moderately narrow. Notal edge completely reduced. Cerata in separate rows, on elevations, numerous per row. Ceratal rows partly branched. Rhinophores perfoliate. Anus mixed (pleuroproctic in a higher acleioproctic position). Jaws with masticatory edges bear several moderate denticles, tuberculate to more sharpened. Radula formula 1.1.1. Central teeth cusp compressed by adjacent lateral denticles. Lateral teeth smooth with moderately attenuated process basally. Distal receptaculum seminis. Vas deferens moderately long, prostate relatively distinct. Supplementary and accessory glands absent. Massive external permanent penial collar absent. Penis internal, narrow, unarmed.

Genera included: Apata Korshunova et al., 2017 and? Tularia Burn, 1966 .

Superfamily Unidentioidea Millen and Hermosillo, 2012 , herein established

( Figs 1–4; Tables 1–3)

Diagnosis: Aeolidacean superfamily with uniserial radula. Notal edge completely reduced. Cerata on indistinct elevations or low stalks. Ceratal rows branched to simple. Rhinophores smooth. Anus pleuroproctic or mixed in a higher acleioproctic position. Anterior foot corners present. Elaborate oral glands commonly present. Jaws with masticatory edges bear a single or several irregular to distinctly sharpened, elongate denticles. Central teeth with non-compressed cusp. Distal and proximal receptaculum seminis or only a proximal receptaculum. Clasping organ in female part of reproductive system absent. Vas deferens moderately long to short, prostate distinct. Supplementary gland absent. Accessory gland absent or, rarely present. Massive external permanent penial collar absent. Penis internal, not considerably widened, armed or unarmed.

Families included: Unidentiidae Millen and Hermosillo, 2012 .

Remarks: Family Unidentiidae in the present study is sister to the superfamily Fionoidea , although not with the highest support ( Figs 1, 2). In other phylogenies Unidentiidae also never nested unequivocally with any of the known Aeolidacean families (see: Korshunova et al. 2017a, 2019b, Karmeinsky et al. 2021, present study; Figs 1, 2). Consistent with the molecular data, morphologically, Unidentiidae represent a bizarre combination of several traits that otherwise can be mosaically found within all three major Aeolidacean superfamilies, Fionoidea , Aeolidioidea , and Flabellinoidea : uniserial radula, reduced notal edge, but at the same time cerata on elevations or low stalks, and a pleuroproctic to higher acleioproctic anus, complemented with the absence of a supplementary gland, but very rarely the presence of a not-well documented accessory gland. Even taxonomically this unusual family, which externally may simultaneously look like ‘a flabellinid’ or a ‘facelinid’, has been highlighted as having features of several, otherwise distantly related superfamilies and its representatives were initially called ‘ Flabellina ’ sensu latissimo ( Gosliner 2010) , but finally were assigned to a completely separate family, remarkably in the molecular era, using only morphological argumentation ( Millen and Hermosillo 2012). Taking into consideration that Unidentiidae never place consistently into any of the Aeolidacean superfamilies, the separate superfamily status for Unidentioidea , herein established, is highly justified.