Mgueolia Korshunova et al. , 2025

Genus Mgueolia Korshunova et al., 2025

( Figs 1, 10)

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Type species: Mgueolia almamater Korshunova et al., 2025

Etymology: In honour of the first, largest and the most famous Russian University, Moscow State Univesity (MGU, Moskovskyi Gosudarstvennyi Universitet in Russian), and its 270-year anniversary in 2025. Additionally, ‘Aeolia’ (short form ‘Eolia’) both refers to aeolidacean nudibranchs and also means a floating island in Greek mythology. ‘Aeolus’ Kingdom can be metaphorically assigned to Moscow State University as a dynamic ‘island’, permanently searching for knowledge and education in an ocean of the world/universe that still needs to be understood. Ultimately, the combination of genus and species name Mgueolia almamater (Alma mater = nourishing mother) refers to both a common symbolic word for any worldwide university to denote a cradle of education, and in reference to the obviously relict nature of the new species and thus its ‘alma mater’ is the middle Kuril Islands, where probably that externally splendid and internally amazing taxon was able to survive.

Diagnosis: Body moderately wide. Notal edge present, continuous. Cerata not stalked, continuous. Rhinophores smooth to wrinkled with some peculiar folds, somewhat shorter or similar in size to oral tentacles. Anterior foot corners present, short. Anus pleuroproctic under the notal edge, but external opening is very difficult to observe both in living and preserved specimens due to the tight adherence of the notal edge with cerata to the body sides. Edges of masticatory processes bear denticles that may form several longitudinal rows of denticles and tubercles from the internal side, diminishing toward the inner part of the jaw. Central teeth with narrow, compressed cusp, the majority of lateral denticles clearly delineated from cusp. Lateral teeth smooth to very weakly serrated/wavy with a long, broad process latero-basally, not significantly smaller than central teeth. Both distal and proximal receptaculum seminis present. Vas deferens long, coiled with several loops, relatively narrow, no distinct prostate. Massive external penial collar absent. Penis elongated conical, unarmed.

Species included: Mgueolia almamater Korshunova et al., 2025 ( Mgueolia almamater Korshunova et al. gen. et sp. nov. in Martynov and Korshunova 2025).

Remarks: Mgueolia almamater Korshunova et al., 2025 , herein for the first time described in detail, according to the molecular phylogenetic data, is robustly placed as a distinct clade of the family Paracoryphellidae , sister to all the genera so far known— Chlamylla , Paracoryphella , and Polaria ( Figs 1, 2)—with external features generally in agreement with all genera of the family Paracoryphellidae (a continuous notal edge and numerous cerata in continuous rows ( Fig. 10A, B, D–I)). However, according to the radular patterns, the new genus is drastically different from all known adult paracoryphellids by the combination of a narrow, compressed cusp of the central tooth and almost smooth lateral teeth with a broad massive latero-basal process ( Fig. 10P), similar to the family Eubranchidae from the completely different and phylogenetically very distantly related superfamily Fionoidea ( Figs 1, 2). The somewhat swollen cerata of the new genus and species also partly recall members of the family Eubranchidae . Thus, Mgueolia almamater is a highly unusual and remarkable taxon, that evolution preserved in the rarely visited and understudied waters of the middle Kurile Islands, and combined both relatively advanced and very archaic features. The discovery and description of Mgueolia almamater represents an important landmark in nudibranch taxonomy.