Occidentella, Korshunova, Tatiana, Martynov, Alexander, Bakken, Torkild, Evertsen, Jussi, Fletcher, Karin, Mudianta, I Wayan, Saito, Hiroshi, Lundin, Kennet, Michael Schroedl, & Picton, Bernard, 2017

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 : 37-38

Occidentella gen. n. Figs 21, 32

Type species.

Coryphella athadona Bergh, 1875.

Etymology.

After the Western Pacific (from occidens = “west” in Latin), where the type species predominantly occurs.

Diagnosis.

Body narrow. Notal ridge completely reduced. Cerata in several groups. Rhinophores smooth. Anterior foot corners absent. Rachidian teeth with non-compressed cusp and distinct denticles. Lateral teeth denticulated without attenuated process basally. Distal and proximal receptaculum seminis. Vas deferens very short, expanding into broad penial sheath with an additional glandular formation. Penis small, amorphous.

Species included.

Occidentella athadona (Bergh, 1875), comb. n. (Fig. 32) (original description in Bergh 1875; redescription in Baba 1987a)

Remarks.

The genus Occidentella with only a single known species O. athadona has unique external and internal morphological features compared to all described Coryphellidae taxa: a rounded anterior part of the foot (no foot corners) and a highly developed glandular part of vas deferens which is similar to a true penial gland in some other families (e.g., Tergipedidae and Eubranchidae ) (Fig. 21). Millen and Hermosillo (2007) indicated that some other taxa, e.g., Coryphella trilineata possess in a some degree a similar glandular structure; however, the penial complex in C. trilineata is still similar (see MacFarland 1966) to other coryphellids and not so obviously separated from the penial sheath as in O. athadona . By other features, e.g., presence of annulated rhinophores and anterior foot corners, C. trilineata differs considerably from O. athadona . Possibly in agreement with data on the similarity of a glandular formation in the penis, C. trilineata is placed within the same clade with O. athadona according to our molecular analysis (Figs 1, 2). However, this result may also be because we do not have molecular data for other coryphellids which are morphologically similar to C. trilineata from the Eastern Pacific (e.g., C. cooperi (Cockerell, 1901), Flabellina fogata Millen & Hermosillo, 2007) and C. trilineata together with these other species will probably be further separated from O. athadona . However, because it is morphologically very different from all other coryphellid taxa, C. athadona deserves its own genus. This is consistent with one of the general rules of integration of morphological and molecular data which were outlined above (see Materials and methods section), when a morphologically strongly aberrant taxon should not be merged with a phylogenetically relatively close taxon. This implies that if we merge the morphologically strongly aberrant C. athadona with the morphologically different but phylogenetically possibly relatively close C. trilineata we will considerably mask the natural diversity and will therefore make further classification much more difficult. If more species are discovered within these species complexes, we will need to compare them with morphologically very disparate taxa instead of making a comparison within narrow morphological and molecular units. According to these principles, the species Coryphella trilineata O’Donoghue, 1921 is separated here into another new genus (see below), within which we tentatively include at least two more Eastern Pacific species C. cooperi and Flabellina fogata Millen & Hermosillo, 2007 with similar external characters (rhinophores annulated in two species and warted in one species) and reproductive features (glandular formation at the base of penis).