Tomoberthella, Moles & Brenzinger & Berning & Martynov & TatianaKorshunova & Schrödl, 2024

Tomoberthella gen. nov.

( Fig. 1H View Figure 1 )

urn:lsid:zoobank.org:act:8D6B1A52-6901-4EF6-853E-0A68B0859EB6 .

Type species: Tomoberthella martensi (Pilsbry, 1896) comb. nov.

Pleurobranchus scutatus E. von Martens, 1880 ( non-Pleurobranchus scutatus Forbes, 1844).

Gymnotoplax martensi Pilsbry , 1896 new name for homonymy; the type species of Gymnotoplax is considered species dubia according to Willan (1978).

Berthella martensi (Pilsbry , 1896).

Diagnosis: Dorsum divided into distinctive, autotomizable areas. Mantle and head delimited by black margins. Jaw platelets’ central cusp broad, with smooth margins.

Etymology: The genus name is constructed in apposition of tomos (Ancient Greek for slice or section) that denotes cut pieces, alluding to the sectorized mantle, and Berthella .

Genre: Feminine.

Remarks: Originally, ‘ Berthella ’ martensi was included in the genus Gymnotoplax (Pilsbry, 1896). However, the type species of the genus Gymnotoplax is Pleurobranchus americanus A.E.Verrill , 1885, collected off the coast of the NE United States in 457 m. The genus Gymnotoplax was originally described to include two species: G. americanus (A.E.Verrill , 1885) and G. martensi Pilsbry , 1896, but the type species was not designated. Posteriorly, Zilch (1959) designated G. americanus as the type species of Gymnotoplax genus, and Marcus (1977) also agreed. An exposed shell was considered characteristic of the genus and thus deserving the erection of Gymnotoplax . Willan (1978, 1987) revised the original material and consistently showed that G. americanus consists of a single specimen with an exposed shell because of a damaged dorsum. Thus, Willan (1978) considered, pending clarification of the identity of its type species, Gymnotoplax as genus dubium. Accordingly, the genus Gymnotoplax cannot be used as a valid name for ‘ Berthella ’ martensi . Moreover, ‘ B. ’ martensi was described based on a juvenile specimen off Mauritius, and Pilsbry (1896) mentioned that this specimen has a frontal incision. This character may be referring to the partite mantle typical of this ‘ martensi group’, and thus specimens with a typical partite mantle from the Indo-Pacific were attributed subsequently to this species. Yet the exposed shell of G. americanus is an artefact that cannot be matched to the partite mantle of ‘ B. ’ martensi . Therefore, according to the morphological diagnosis, we erect the new genus Tomoberthella gen. nov. for martensi species described by Pilsbry (1896). Molecular data further reinforces the morphological uniqueness of Tomoberthella martensi comb. nov., which appears as a distinct clade sister to the species of Pleurehdera , and most probably represents a species complex.