Himatina Thiele, 1931, reinstated (Figs 1, 2, 13; Table 5) Thiele 1931: 453. Korshunova et al. 2017a: 39. Type species: Himatella trophina Bergh, 1894. Diagnosis: Body wide. Notal edge present, continuous. Cerata in continuous rows. Rhinophores perfoliate. Anterior foot corners present. Central teeth almost pectinate, with moderately compressed apically narrow, basally distinctly widened cusp (in some posterior teeth the cusp can be reduced), and distinct, strong denticles. Lateral teeth denticulated with strongly attenuated process basally. Distal and proximal receptaculum seminis. Very short vas deferens expands into a broad penial sheath, prostate indistinct. Penis broad, discoid. Species included: Himatina trophina (Bergh, 1894) comb nov .. Detailed morphological data in Korshunova et al. (2017a). Remarks: The genus Himatina was described more than 100 years ago, even without, at that time, the aid of molecular data, due to its immediate external and radular differences from any other coryphellid genera (Bergh 1894, Thiele 1931). The broad body of Himatina with its continuous notal edge represents an ancestral feature, more characteristic of the family Paracoryphellidae, than for the majority of Coryphellidae genera with their discontinuous or completely reduced notal edge. Perfoliate rhinophores are also very rarely present, especially in boreal Coryphellidae, being more characteristic of the families Flabellinidae and Facelinidae, and some warm-water coryphellids (see below). The radula of Himatina, with an almost pectinate general pattern, both central and lateral teeth strongly denticulated (the latter with a strongly attenuated process basally), is significantly different from all Coryphellidae, and by its general pattern more similar to the phylogenetically distantly related genus Polaria from the family Paracoryphellidae (Korshunova et al. 2017a), than to any other true coryphellid genera. In total, the genus Himatina is different from any known genera of the family Coryphellidae by the combination of a wide body, perfoliate rhinophores, almost pectinate central teeth, and a very short vas deferens. Comparison of the genus Himatina with all valid, currently included Coryphellidae genera is presented in Table 5.

Published as part of Korshunova, Tatiana, Fletcher, Karin & Martynov, Alexander, 2025, The endless forms are the most differentiated-how taxonomic pseudo-optimization masked natural diversity and evolution: the nudibranch case in Zoological Journal of the Linnean Society 204 (4), DOI: 10.1093/zoolinnean/zlaf057