Facelinidae Bergh, 1889

Family Facelinidae Bergh, 1889 View in CoL s.l.

( Figs 1, 2; Table 4)

Subfam. Facelininae Bergh 1889: 213 .

Family Facelinidae View in CoL ‘ Odhner 1939 ’ Odhner in Franc 1968: 886. Korshunova et al. 2017a: supplementary materials (part., not yet separated from Myrrhinidae View in CoL ).

Diagnosis: Body moderate to narrow. Notal edge commonly completely reduced or some lateral extensions formed. Cerata without distinct elevations, commonly numerous per row. Ceratal rows simple, arched, or branched. Rhinophores smooth, annulate, perfoliate, papillate, or covered with complex folds and wrinkles. Anus commonly cleioproctic, rarely acleioproctic or pleuroproctic. Masticatory edges of jaws moderately denticulated with single or more rows of blunt or sharpened denticles, sometimes partly compound, or smooth. Radula formula 0.1.0. Central teeth with largely non-compressed, but sometimes compressed, cusp, rarely pectinate. Distal and proximal receptaculum seminis or only proximal receptaculum. Vas deferens long to short, prostate indistinct or distinct. Accessory gland absent or present. Massive external permanent penial collar absent. Penis internal, narrow, or broad, unarmed or armed with several or single stylets or spines, sometimes partly glandular, in addition can be covered with various papillae, flaps or lobes.

Genera included: Adfacelina Millen and Hermosillo, 2012 , Algarvia Garcia-Gomez and Cervera, 1990 , Amanda Macnae, 1954 , Anetarca Gosliner, 1991 , Antonietta Schmekel, 1966 , Austraeolis Burn, 1962 , Bajaeolis Gosliner and Behrens, 1986 , Burnaia Miller, 2001 , Caloria Trinchese, 1888 , Cratena Bergh, 1864 , Dicata Schmekel 1967 , Echinopsole Macnae, 1954 , Emarcusia Roller, 1972 , Facelina Alder and Hancock, 1855 , Facelinopsis Pruvot-Fol, 1954 , Hermosita Gosliner and Behrens, 1986 , Herviella Baba, 1949 , Janssonius Ortea and Moro, 2022 , Jason Miller, 1974 , Learchis Bergh, 1896 , Moridilla Bergh, 1888 , Myja Bergh 1896 , Noumeaella Risbec, 1937 , Palisa Edmunds, 1964 , Pauleo Millen and Hamann, 1992 , Phidiana Gray, 1850 , Pruvotfolia Tardy, 1969 , Pteraeolidia Bergh, 1875 , Sakuraeolis Baba, 1965 , and Setoeolis Baba and Hamatani, 1965 .

Remarks: The family Facelinidae , even in a restricted sense ( Martynov et al. 2019), with perhaps the largest composition by genus-level within the suborder Aeolidacea and an almost maximally possible number of genera, well demonstrates the profound relativeness of the still currently employed typological taxonomic methods rooted in the basically anti-evolutionary works by Linnaeus (e.g. 1758), that persist in the apparently strictly ‘phylogenetic’ era. The diagnoses of so many genera represent the finest level of morphology-based differentiated taxonomy. So the question is why, on the one hand, are genera allowed that include only a few species per genus or monotypic (e.g. Millen and Hamann 1992, Millen and Hermosillo 2012, Gosliner et al. 2015) in one family, but on the other hand obvious and undisputable morphological and molecular diversity is completely denied or suppressed within, for example, the superfamily Flabellinoidea ( Gosliner and Griffiths 1981, Gosliner et al. 2015) or the family Coryphellidae ( Ekimova et al. 2022) . Simultaneously keeping the numerous finely differentiated Facelinidae genera, and the fundamentally typology-based anti-evolutionary style that implies, while using various completely non-scientific arguments to make a decision such as ‘didactic simplicity’, ‘tradition’, ‘usage by some putative “authority”’ (e.g. Epstein et al. 2018, Gosliner et al. 2018) for the validity of a taxon, is both illogical and counter to actual evolutionary processes.

If we really want to see systematics (taxonomy) as a true science, not as some branch of subjective and seemingly random decision-making, then we must follow the true mosaicism of evolution and not decide that something is ‘oversplit’ when the conclusions are non-traditional or inconvenient for humans. That is why the term ‘splitters’, along with the entire ‘splitter-lumper’ unpleasant dichotomy [see especially the case described by Willan (2021) for oyster taxonomy; see also Discussion], must be completely removed from scientific arguments (Korshunova et al. 2022). And as we thoroughly argued previously and throughout the present study, the only scientific alternative to the ‘policy-based’ non-scientific bias in current taxonomy is the use of maximal fine-scale taxonomic differentiation, where finer and finer scale morphological and molecular groups must be not disregarded, but instead recognized to a maximal degree ( Figs 1, 2). While this methodology, as in any scientific endeavour, is not free from problems and inconsistencies (see: Korshunova et al. 2022), it is the only reliable alternative to the currently commonly employed manner of doing taxonomy—when a phylogenetic tree is obtained, based on some not always clearly explained taxon selection, and some apparently monophyletic groups are afterwards detected, then the ‘taxonomic arrangement’ of how many ‘species’, genera, families, and so on to be recognized is matter of largely non-evolutionary, non-scientific argumentation of ‘general policy in a given group’, plainly understood ‘usability’, and, ultimately, ‘authority-approval’. All these highly archaic and cautious-sounding (but still persistent in taxonomy at a practical level) ‘set of methods’ must definitely be changed if we really want a coherent future for both our very old and very modern, basic biological science of systematics (taxonomy).

The family Facelinidae in its current genera composition is obviously still too heterogenous, both at a morphological and a molecular level, even after removing the families Myrrhinidae ( Martynov et al. 2019) and Favorinidae (present study; Figs 1, 2), and definitely more family-level taxa need to be recognized within the current ‘ Facelinidae s.l.’.