Metalycaeus polygonoma (W.T. Blanford, 1862)

Figs 83–88

Alycaeus polygonoma W.T. Blanford, 1862: 140–141 .

Alycaeus distinctus Godwin-Austen, 1893: 592 . Syn. nov.

Alycaeus rotundatus Godwin-Austen, 1914: 359, pl. 154 fig. 6. Syn. nov.

Alycaeus kamakiaensis Godwin-Austen, 1914: 375–376, pl. 141 fig. 8. Syn. nov.

Metalycaeus posteriobulbus Gittenberger & Sherub Sherub in Gittenberger et al., 2024: 193, figs 1, 6–7. Syn. nov.

Alycaeus ingrami var. – Godwin-Austen 1871: 91–92, pl. 4 fig. 3.

Alycaeus polygonus [sic] – Sowerby 1877: pl. 2, species 11.

Alycaeus (Dicharax) polygonoma – Kobelt 1902: 375. — Gude 1921: 265–266. Alycaeus polygonoma – Godwin-Austen 1914: 423, pl. 141 fig. 5.

Alycaeus distinctus – Godwin-Austen 1914: 363; 1914: 390, pl. 145 figs 3, 3a–b.

Alycaeus distinctus var. – Godwin-Austen 1914: 363, pl. 137 figs 2, 2a–b, 391, pl. 149 fig. 4 (2 varieties). Alycaeus kamakiaensis – Gude 1921: 209.

Alycaeus rotundatus – Gude 1921: 217.

Alycaeus (Chamalycaeus) distinctus – Gude 1921: 226–227.

Alycaeus (Alycaeus) kamakiaensis – Ramakrishna et al. 2010: 48.

Alycaeus (Alycaeus) rotundatus – Ramakrishna et al. 2010: 51.

Chamalycaeus (Chamalycaeus) distinctus – Ramakrishna et al. 2010: 53.

Metalycaeus distinctus – Páll-Gergely et al. 2020: 142.

Metalycaeus kamakiaensis – Páll-Gergely et al. 2020: 145.

Metalycaeus polygonoma – Páll-Gergely et al. 2020: 151.

Metalycaeus rotundatus – Páll-Gergely et al. 2020: 153.

Diagnosis

This species can be recognised based on the relatively large aperture, finely undulated peristome, the elongated basal peristome edge and the blunt centrally located R3 swelling. We indicate that the Himalayan species of Metalycaeus are not revised in this study, and a comprehensive revision should identify the species-specific traits.

Type material examined

INDIA • 10 syntypes of A. distinctus (Fig. 83F–J); Naga Hills; NHMUK 1903.7.1.2619 • 1 syntype of A. kamakiaensis (Fig. 84A–E); Kamakia Hill, Gowhatty, Assam; NHMUK 1903.7.1.2705 • holotype (single shell mentioned in the original description: Fig. 83F–J) of A. rotundatus; Dafla Hills (?); NHMUK 1903.7.1.2543 .

MYANMAR • 2 syntypes of A. polygonoma in different vials (Fig. 83A–E); Tongoop Pass, Arakan Hills; NHMUK 1906.4.4.51 .

Additional material examined

BANGLADESH • 2 shells (Fig. 88); Chittagong, natural mango garden on a river bank; 22°31.559′ N, 92°7.652′ E; 27 Sep. 2024; T. Saito and M.S. Shariar leg.; Coll. PGB .

INDIA • 2 shells of “ Alycaeus distinctus var.”; Sadia, Assam; NHMUK 1903.7.1.2620 • 19 + 6 shells of “ Alycaeus distinctus var.”; Jatinga Valley, N. Cachar; Godwin-Austen coll.; NHMUK 1903.7.1.2576 • 1 empty shell (Figs 12D, 85); Blue Mountain, Lawngtlai district; 22.727° N, 93.135° E; 1400 m a.s.l.; 27 Jan. 2019; N.A. Aravind leg.; Ar48; NZSI LM1762 • 2 empty shells (Figs 86–87 [operculum]); same data as for preceding; Ar71; NZSI LM1763 • 1 empty shell; same data as for preceding; Ar43; NZSI LM1909 • 5 empty shells; same data as for preceding; Ar46; NZSI LM1910 • 2 empty shells; same data as for preceding; Ar51; NZSI LM1911 .

Type localities

“in montibus Arakanensibus” ( A. polygonoma); “Neighbourhood of Asálú, N. Cachar Hills” ( A. distinctus); “Kamakia Temple Hill near Gowhatty, Assam ” ( A. kamakiaensis); “Dafla hills” ( A. rotundatus); “ Zhemgang Dzongkhag: between Duenmang Tsachu and Gongphu Zero Point, 24 km SE of Zhemgang, 335 m a.s.l., 27°02’N 90°48’E, scree in warm broadleaf forest” ( M. posteriobulbus).

Distribution

The new information reveals that M. polygonoma has a larger distribution than previously thought; its area spans from Bhutan and the Dafla Hills (India) to the Arakan Mountains in Myanmar (Fig. 89). Furthermore, this species is reported from Bangladesh for the first time. With these localities, M. polygonoma is one of the few species of Alycaeinae with a large distributional area besides Metalycaeus heudei (Páll-Gergely et al. 2017, 2021), Dicharax fimbriatus and D. cristatus (Möllendorff, 1886) (see Páll-Gergely et al. 2017).

Remarks

Type specimens of A. polygonoma, A. distinctus, A. kamakiaensis, A. rotundatus and M. posteriobulbus do not differ in any important conchological characters; therefore, the latter four are junior synonyms of the former. The types of those five species and the newly collected samples from the Blue Mountain show slight variability in shell size, length of R2, width of umbilicus, and the degree of undulation of the peristome, but all differences are attributed to intraspecific variability.