Ditropopsis E.A. Smith, 1897

Vermeulen, Jaap J., Liew, Thor-Seng & Schilthuizen, Menno, 2015, Additions to the knowledge of the land snails of Sabah (Malaysia, Borneo), including 48 new species, ZooKeys 531, pp. 1-139 : 11

Taxon classification Animalia Architaenioglossa Cyclophoridae

Genus Ditropopsis E.A. Smith, 1897

Ditropopsis E.A. Smith, 1897: 416; Fukuda 2000: 1.

Cyclophorus subgenus Ditropis Blanford, 1869: 126. Genus Ditropis Hanley & Theobald, 1875: xiv.

Ditropopsis [Not Ditropis Kirschbaum ( Delphacidae , Hemiptera )]

Diagnosis for the Sabah species.

Shell very small, white to pale corneous or pale greenish, without any colour patterns. Surface shiny or glossy. Spire rather high-conical, to approx. flat with a protruding apex. Radial sculpture absent or inconspicuous. Spiral sculpture prominent, consisting of distinct cords and keels. Peristome simple or double, expanded or not, without a notch in the angular corner. Height up to 2.3 mm. Umbilicus wide.

Cross diagnosis.

Borneo species of Japonia Gould, 1859 (s.l., including Pilosphaera Lee et al., 2008), have larger shells: usually more than 4 mm high or more. Japonia also has a notch in the angular corner of the peristome, and many have shells with brown colour markings. Only Japonia hyalina Vermeulen & Junau, 2007, and Japonia ditropis Vermeulen & Junau, 2007, from Sarawak, have whitish shells 2.0-3.5 mm high. These two differ from Ditropopsis by having a more distinct radial sculpture.

The two Borneo species of Craspedotropis Blanford, 1864, see Vermeulen 1999, differ by having a narrower umbilicus and more prominent radial sculpture.

We provide a review of the Sabah species of the genus.

Remarks.

The cyclophorid fauna of Borneo includes a small number of species with small shells with conspicuous spiral cords: Jerdonia (?) borneensis Godwin Austen, 1889, Cyathopoma everetti E.A. Smith, 1895, Craspedotropis andrei Vermeulen, 1999 and Craspedotropis juvenilis Vermeulen, 1999. Except for the second species, all were included in Craspedotropis Blanford, 1864 by Vermeulen (1999) with due expression of doubt. His concern was the general similarity of Craspedotropis with two largely continental Asiatic genera Cyathopoma Blanford, 1864, and Jerdonia Blanford & Blanford, 1861. Diagnostic differences between the three are mainly sought in the operculum morphology, a part unfortunately missing in the material of his two new species. The matter is still unresolved, and further complicated when, as we do here, we include Bornean species that show similarity with a fourth genus Ditropopsis E.A. Smith, 1897 = Ditropis Blanford, 1869. Operculum morphology, again, is not decisive, although the operculum of Ditropis koperbergi (Zilch, 1955), see below, differs from that of Craspedotropis borneensis (Godwin Austen, 1889) in lacking the erect and outwards folded whorl edges. However, Ditropis aenigmatica (Van Benthem Jutting, 1963) (Biak Island, Indonesia) and Ditropis heterospirifera (Van Benthem Jutting, 1958) (from Misool Island, Indonesia) are similar to our Bornean species in general terms, but have an operculum with very distinct, erect, calcareous whorl edges.

For the Borneo material we conclude that the species listed below generally differ from the ones included in Craspedotropis by Vermeulen, 1999 by having a wider umbilicus and a less distinct radial sculpture. Their shell morphology agrees well with species generally included in Ditropopsis , and we include them in that genus. Below, we list all the Sabah species present in the collections available to us.

We divide the genus into three informal groups.