Placuna placenta ( Linnaeus, 1758 )

Jirapatrasilp, Parin, Cuny, Gilles, Kocsis, László, Sutcharit, Chirasak, Ngamnisai, Nom, Charoentitirat, Thasinee, Kumpitak, Satapat & Suraprasit, Kantapon, 2024, Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand, ZooKeys 1202, pp. 1-110 : 1-110

Placuna placenta ( Linnaeus, 1758)

Figs 13 A , 14 E

Anomia placenta Linnaeus, 1758: 703. Type locality: unknown.

Placuna placenta . Lynge 1909: 107 – 108. Tantanasiriwong 1979: 6. Morris and Purchon 1981: 324. Nateewathana et al. 1981: 64. Oliver 1992: 86, pl. 17, fig. 6 a, b. Bosch et al. 1995: 234, fig. 1018. Poutiers 1998 a: 218, with in-text figs. Aungtonya et al. 1999: 376. Subba Rao and Dey 2000: 230. Swennen et al. 2001: 46, 76, text-fig. 80, fig. 80. Robba et al. 2002: 77, pl. 6, fig. 10 a, b. Hylleberg and Kilburn 2003: 169 – 170. Robba et al. 2003: table 5. Dharma 2005: 246, pl. 98, fig. 17. Dey and Ramakrishna 2007: 154, 197. Robba et al. 2007: 84 (appendix). Nabhitabhata 2009: 20, with in-text fig., 347. Huber 2010: 190, with in-text fig. Sanpanich 2011: table 2. Huber 2015: C 5627. Yang et al. 2017: 176, fig. 681. Surakiatchai et al. 2018: table 6, pl. 3, fig. 8 a, b. Tudu et al. 2018: table 1. Wells et al. 2021: 64.

Placuna (Placuna) placenta . Dheeradilok et al. 1984: pl. 2, fig. 14. Thach 2005: 266, pl. 81, fig. 4.

Referred material.

CUF - NKNY - B 22 (19 L + 18 R shells; Figs 13 A , 14 E ).

Habitat.

Sandy mud in intertidal zones and shallow waters down to 35 m depth, in quiet waters of lagoons, protected bays, and mangrove areas, or near estuaries ( Poutiers 1998 a; Thach 2005; Yang et al. 2017).

Distribution.

Indian Ocean; Indo-West Pacific, from Japan to Australia ( Huber 2015). Records of fossils from the Late Miocene to Holocene in Indonesia, Japan, the Philippines, Taiwan, and Thailand ( Robba et al. 2002; Surakiatchai et al. 2018).

Record in Thailand.

Gulf of Thailand and Andaman Sea ( Wells et al. 2021).

Taxonomic remarks and comparisons.

This species differs from its similar species, Placuna ephippium (Philipsson, 1788) , by having an almost circular shell and a right valve bearing a hinge plate with arrowhead-shaped lamellar teeth with the posterior ridge distinctly longer than the anterior one ( Poutiers 1998 a; Swennen et al. 2001).

Superfamily Pectinoidea Rafinesque, 1815

Figures

Figure 13. Size comparison of bivalves and other invertebrates found in this study A Placuna placenta B Standella pellucida C Geloina bengalensis D Anadara inaequivalvis E Pegophysema bialata F Megabalanus cf. tintinnabulum G Cultellus maximus H Lutraria complanata I Thalassina sp. J Tellinides conspicuus.

Figure 14. Bivalves A Tegillarca nodifera B Estellacar olivacea C Noetiella pectunculiformis D Magallana cf. gigas E Placuna placenta F Volachlamys singaporina.