Metalycaeus anas Páll-Gergely & A. Reischütz, 2021

Páll-Gergely, Barna, Hunyadi, András, Grego, Jozef, Reischütz, Alexander & Auffenberg, Kurt, 2021, Nineteen new species of Alycaeidae from Myanmar and Thailand (Gastropoda: Caenogastropoda: Cyclophoroidea), Zootaxa 4973 (1), pp. 1-61 : 45-48

Metalycaeus anas Páll-Gergely & A. Reischütz n. sp.

Figs 35–36

Material examined. Holotype: Thailand, Chiang Rai Province, Wat Phra That Tham Doi Khong Khao Meditation Centre, ca. 8 km W of Chiang Rai, cave clay at entrance of cave, 19°54.771’N, 99°46.607’E, ca. 420 m a.s.l. (locality code: Th6), Sep. 2007, A. Reischütz leg., NHMW 113489 (D: 3.3 mm, H: 2.05 mm) . Paratypes: 1 shell (fig. 35B), same data as holotype, NHMW 113490 ; 7 shells, same data as holotype, RE ; 2 shells, same data as holotype, CUMZ 5270 . Other Material: 4 broken shells, same data as holotype, RE .

Etymology. The specific epithet (noun in apposition) derives from the shape of R3 that resembles a duck’s beak ( anas = duck in Latin).

Diagnosis. A medium-sized Metalycaeus species with a weakly sculptured R1 (fine growth lines and spiral striae), almost smooth R2, a R3 with convex, central swelling and a rounded aperture.

Description. Shell light grey, probably somewhat translucent when fresh; shell outline slightly oval in dorsal view, spire somewhat elevated, low conical; body whorl rounded (rather “parabolic”); protoconch conspicuously large to shell size, somewhat elevated, last whorl spirally striated, 1.5 whorls; R1 of 1.25 whorls, with very weak ribs (growth lines) occasionally moderately strong near suture, and fine spiral striations; boundary between R1 and R2 distinct due to R2 axial sculpture; R2 with narrow, somewhat elevated light-coloured stripes alternating with broader, darker stripes, ca. 24–32 R2 stripes present; R2+R3 approximately or slightly more than quarter whorl; R2 slightly shorter than R3; R3 practically smooth, bearing only low growth lines; boundary between R2 and R3 distinct due to lack of R3 light stripes (ribs) and rather deep constriction; R3 with elevated, convex central swelling with anterior slope steeper than posterior; aperture strongly oblique to shell axis; round; boundary between inner and outer peristomes distinct; inner peristome protruding, expanded, rather slim; outer peristome of comparable strength, expanded, and slightly reflected toward umbilicus; umbilicus relatively narrow, approximately one fourth the shell width.

A cross-sectional view of R2 of one specimen was examined ( Fig. 36E–G ): anterior crust very slightly elevated, forming very low, blunt rib; anterior crust and the slightly weaker posterior crust adnate, forming slender microtunnel in cross-sectional view.

Measurements. D: 3.3–3.91 mm, H: 2.05–2.26 mm.

Operculum. unknown.

Differential diagnosis. Metalycaeus rubinus (Godwin-Austen, 1893) (examined material: Ruby Mines District, Up. Burma, leg. Doherty, NHMUK 1903.7.1.2685, 2 syntypes, Fig. 37 ) is the only Metalycaeus species reported from Myanmar having atypical R2 ribbing. It is far larger and has an elevated spire.

Distribution. This new species is known only from the type locality ( Fig. 17 ).

Figures

FIGURE 17. Distribution of alycaeid species in northern Thailand and Myanmar. filled circle: Dicharax admirandus Páll- Gergely & Auffenberg, n. sp., empty square: Dicharax ebrius Páll-Gergely & Auffenberg, n. sp., filled triangle: Dicharax gnomus Páll-Gergely, n. sp., filled square: Dicharax mirounga Páll-Gergely, n. sp., inverted empty triangles: Dicharax verruco- sus Páll-Gergely & Hunyadi n. sp., rhombus: Dicharax stuparum Páll-Gergely & Hunyadi, 2018, empty triangle: Metalycaeus anas Páll-Gergely & A. Reischütz, n. sp.

FIGURE 35. Metalycaeus anas Páll-Gergely & A. Reischütz n. sp., A: holotype (NHMW 113489); B: paratype (NHMW 113490).

FIGURE 36. Shell sculpture of Metalycaeus anas Páll-Gergely & A. Reischütz n. sp., A–D: holotype (NHMW 113489); E–G: cross-sectional view of R2 (paratype from the type locality, RE). Abbreviations: a—anterior crust; p—posterior crust; t—microtunnel.

FIGURE 37. Metalycaeus rubinus (Godwin-Austen, 1893), syntype (NHMUK 1903.7.1.2685).