Cassidula nucleus (Gmelin, 1791)

Figs 4 L, 11 C

Helix nucleus Gmelin, 1791: 3193. Type locality: “ Tahiti ” [Cooktown, Queensland, Australia].

Auricula mustelina Deshayes, 1830: 92. Type locality: “ New Zealand ”.

Cassidula nucleus. Cernohorsky 1972: 212, pl. 60, fig. 8. Bosch et al. 1995: 183, fig. 851. Subba Rao and Dey 2000: 188. Swennen et al. 2001: 60, 143, fig. 526. Hylleberg and Kilburn 2003: 133. Robba et al. 2004: 242 – 243, pl. 35, fig. 6. Dharma 2005: 208, pl. 79, fig. 1 a, b. Thach 2005: 233, pl. 72, fig. 8. Dey 2006: 55 – 56, figs 73, 74. Raven and Vermeulen 2007: 50 – 51, pl. 4, figs 35, 36. Robba et al. 2007: 98 (appendix). Kesavan et al. 2009: 382, with in-text fig. Nabhitabhata 2009: 227. Groh 2010: 448, pl. 915, figs 9 – 11. Zvonareva and Kantor 2016: 429 – 430, fig. 8 s, t. BEDO 2017 b: 80, with in-text fig. Kantharajan et al. 2017: table 1, fig. 4 - 32. Yang et al. 2017: 134, fig. 545. Tudu et al. 2018: table 1. Wells et al. 2021: 145.

Cassidula mustelina. Brandt 1974: 221, pl. 16, fig. 88. Tantanasiriwong 1978: 20, fig. 259. Nateewathana et al. 1981: 62. Way and Purchon 1981: 321. Hylleberg and Kilburn 2003: 133. Sri-aroon et al. 2004: table 1, fig. 2 - 9. Sri-aroon et al. 2005: tables 2 – 6. Dechruksa et al. 2014: fig. 3 c. BEDO 2017 b: 80, with in-text fig. Okutani 2017: 1128, pl. 427, fig. 4.

Referred material.

CUF - NKNY - G 63 (1 shell; Figs 4 L, 11 C).

Habitat.

On mud in shaded areas and on tree trunks in mangrove and nipa palm forests, sometimes present in salt marsh or on muddy tidal flats (Brandt 1974; Raven and Vermeulen 2007; Zvonareva and Kantor 2016).

Distribution.

Arabian Gulf and Indian Ocean; Indo-West Pacific, from Japan to Australia (Brandt 1974; Bosch et al. 1995; Subba Rao and Dey 2000; Okutani 2017). Records of fossils from the Holocene in Thailand (Robba et al. 2004).

Record in Thailand.

Gulf of Thailand and Andaman Sea (Brandt 1974; Swennen et al. 2001; Wells et al. 2021).

Taxonomic remarks and comparisons.

This species differs from its similar species, Cassidula aurisfelis (Bruguière, 1789), by having a normal and non-bifurcated columellar fold, a less rounded outline with a less convex shoulder, a straighter aperture, and a thinner palatal ridge (Raven and Vermeulen 2007). See also comprehensive taxonomic remarks in Raven and Vermeulen (2007).

Class Bivalvia Linnaeus, 1758

Subclass Protobranchia Pelseneer, 1889

Order Nuculanida Carter et al., 2000

Superfamily Nuculanoidea H. Adams & A. Adams, 1858