Metalycaeus Pilsbry, 1900

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 Metalycaeus Pilsbry, 1900

Alycaeus (Metalycaeus) Pilsbry, 1900: 382. (section of Alycaeus )

Raptomphalus Godwin-Austen, 1914: 366. syn. nov.

Metalycaeus - Bollinger 1918: 316; Páll-Gergely and Asami 2017: 4; Páll-Gergely et al. 2017: 73.

Chamalycaeus (Metalycaeus) - Thiele 1929: 108; Wenz 1938: 478; Egorov 2013: 37.

Chamalycaeus (Raptomphalus) - Thiele 1929: 108; Wenz 1938: 478; Egorov 2013: 37-38.

Type species.

Alycaeus (Metalycaeus) melanopoma Pilsbry, 1900 (Fig. 31A ) (junior synonym of Chamalycaeus nipponensis [Reinhardt, 1877], see Minato 1988), SD Thiele (1929: 108).

Diagnosis.

Shell small to very large (D: 3-10 mm), spire usually low, protoconch usually elevated, spirally striated (key character); spiral striation of protoconch very rarely absent (see under M. laevis ); R1 usually reticulated with sometimes prominent radial ribs; spiral lines always present on the teleoconch; R2 rarely short, usually long to very long, sometimes entirely smooth, but typically with widely spaced, straight, sharp ribs; R3 usually well-developed, although can be reduced. Operculum thin or relatively thickened, sometimes with funnel-shaped outer surface caused by the modification of the multispiral outer laminae. Radula usual for the family (central tooth with five cusps, broad, central cusp pointed).

Differential diagnosis.

Metalycaeus is recognised based on the spirally striated protoconch, which distinguishes Metalycaeus from species assigned to all other alycaeid genera.

Distribution.

Metalycaeus is widely distributed from the southeastern Himalaya to the south of Honshu Island (Japan) and the northern islands of the Philippines, but it does not extend any further south than northern Laos and Vietnam (Fig. 9 ).

The Metalycaeus records in Páll-Gergely and Auffenberg (2019) from Borneo ( Chamalycaeus everetti ) and Sumatra ( Chamalycaeus sumatranus ) later proved to be Chamalycaeus species.

Remarks.

The type species of Raptomphalus ( Metalycaeus magnificus ) (Fig. 31B ) and M. oakesi have a prominently keeled umbilicus which serve as the distinctive character for the genus Raptomphalus . A less prominently keeled umbilicus is observable in other species, such as Chamalycaeus vulcani and Metalycaeus brahma , which can be interpreted as intermediate forms between the non-keeled umbilicus of alycaeids and the keeled umbilicus of Raptomphalus . Moreover, a variety of Metalycaeus brahma has much less prominent umbilical keel than typical species in the genus. Therefore, the keeled umbilicus cannot serve as a distinctive character between genera. Consequently, Raptomphalus is a synonym of Metalycaeus .

For sake of simplicity, this genus is divided here into typical and atypical (or questionable) species. The first includes those having sharp, widely spaced R2 ribs, whereas the second includes species with R2 sculpture other than typical, including those which could not be examined.

Figures

Figure 9. Distribution of Chamalycaeus Moellendorff, 1897 (dark shaded area) and Metalycaeus Pilsbry, 1900 (light shaded area).

Figure 31. Type species of alycaeid genus-group taxa A Alycaeus melanopoma Pilsbry, 1900 (synonym of Chamalycaeus nipponensis (Reinhardt, 1877 )), lectotype (ANSP 78815; type species of Metalycaeus); B Metalycaeus magnificus (Godwin-Austen, 1914), syntype (NHMUK 1903.7.1.3115; type species of Raptomphalus). Photographs: downloaded from the website of ANSP (A), Harold Taylor (B).