Dioryx Benson, 1859

Pall-Gergely, Barna, Sajan, Sheikh, Tripathy, Basudev, Meng, Kaibaryer, Asami, Takahiro & Ablett, Jonathan D., 2020, Genus-level revision of the Alycaeidae (Gastropoda, Cyclophoroidea), with an annotated species catalogue, ZooKeys 981, pp. 1-220 : 1

Genus Dioryx Benson, 1859

Dioryx Benson, 1859: 177. [section (subgenus) of Alycaeus ]

Dioryx - Kobelt and Möllendorff 1897: 146; Gude 1921: 198; Thiele 1929: 107; Wenz 1938: 477; Egorov 2013: 34.

Type species.

Alycaeus amphora Benson, 1856 (Fig. 26 ), SD Gude (1921: 198).

Diagnosis.

Shell small to very large (3.5-9 mm), globose, sometimes the body whorl is angled or keeled; protoconch smooth, not spirally striated; R1 usually very finely reticulated due to fine radial ribs and fine spiral striation, or smooth; R2 short to long, usually without ribs (superficially smooth, with alternating lighter and darker stripes); R3 practically absent (the inner opening of the sutural tube is situated close to the aperture). Operculum thin, usually proteinaceous ( “horny”), in some species can be thicker, calcified. Central tooth with 5-7 cusps, broad, central cusp blunt.

Differential diagnosis.

The combination of the globular shell, the reduced sculpture (only very fine spiral and radial lines are present), and the absence of the R2 region characteristic for the vast majority of alycaeid species make Dioryx species distinguishable from other alycaeid genera.

Distribution.

Dioryx is distributed from the southeastern Himalayan region to Taiwan in the east, and down to the northern part of the Malay Peninsula and southern Vietnam in the south (Fig. 7 ).

Remarks.

Dioryx is primarily classified based on the reduced R3. This character state is found in other genera of the Alycaeidae as well, such as in Alycaeus conformis , Chamalycaeus microconus , and in Awalycaeus (treated as a synonym of Dicharax ). Even presuming that similar morphology has appeared multiple times in the Alycaeidae , we can reasonably assume the monophyly of Dioryx due to the uniform, simple sculpture across all species, and the generally globose shell.

Figures

Figure 7. Distribution of Alycaeus Gray, 1850 (dark shaded area) and Dioryx Benson, 1859 (light shaded area).

Figure 26. Dioryx amphora (Benson, 1856), probable syntype (UMZC I. 102850; type species of Dioryx). Photographs: Harold Taylor (NHM).