Schistoloma Kobelt, 1902

Páll-Gergely, Barna, Nguyen, Phi Khanh & Chen, Yansen, 2019, A review of Vietnamese Schistoloma Kobelt, 1902 with a list of all known species of the genus (Caenogastropoda: Cyclophoroidea: Pupinidae), Raffles Bulletin of Zoology 67, pp. 322-327 : 322-323

Genus Schistoloma Kobelt, 1902

Schistoloma Kobelt, 1902: 298 (nom. nov. pro Coptocheilus Gould, 1862 ).

Pinteria Varga, 1972: 134 (type species: Pinteria croesus Varga, 1972 , by original designation)

Schistoloma (Hololoma) Bartsch, 1916: 195 (type species: Megalomastoma quadrasi Hidalgo, 1889 , by monotypy).

Type species. Cyclostoma altum Sowerby, 1842 by original designation.

Diagnosis. Shell high conical to elongate oviform, sculpture mostly smooth, rarely ribbed, periumbilical keel present or absent, aperture rounded without any tubes or slits, operculum corneous, multispiral, the individual coils overlap with each other and fuse only at their centre.

Remarks. It is obvious that the Vietnamese members of Schistoloma can be divided into two groups. Namely, one with a periumbilical keel (S. cochinchinense, S. messageri ) and one without ( S. inermis , S. maydelineae new species). The presence or absence of this character has been used as a distinguishing mark on the genus level in other pupinid genera ( Páll-Gergely et al., 2015). In the Philippine members of this genus however, there is a continuous variability between those two types. Therefore, it is not suggested to subdivide the genus based on this character at the moment. The subgenus Hololoma Bartsch, 1916 is said to have a narrow slit in the upper edge of the aperture, but this character is not clear in the illustrations of Bartsch (1916). Even if a slight slit is present in some species, it might not be sensible to split the genus based on this character with our current understanding, especially because this is only the edge of the distribution of the genus, and it is unlikely that the nominal genus has an extremely wide distribution. Given the large geographical area and the simple shell, it is possible that the genus Schistoloma is a group of species with plesiomorphic characters, and therefore, not monophyletic. Keeled species might be phylogenetically closer to Tortulosa Gray, 1847 , than to non-keeled Schistoloma species.