taxonID	type	description	language	source
038E878C7B43FFA3DFB1FF03FC8BFAD5.taxon	description	(Fig. 4 D – F) Ostrea belcheri Sowerby II, 1871 (in 1870 – 1871): pl. 7, fig. 11 (type locality: “ Eastern Seas? ”).	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B43FFA3DFB1FF03FC8BFAD5.taxon	materials_examined	Material examined. Site 2, Samaesan seafood market. Published Gulf of Thailand records. Crassostrea belcheri (Sowerby II, 1871): Chaitiamwong et al. (1971); Aungtonya et al. (1999); Yoosukh & Duangdee (1999); Day et al. (2000); Klinbunga et al. (2000, 2001, 2002, 2003, 2005); Yoosukh (2000); Bussarawit & Simonsen (2006 a); ONEP (2007); Nabhitabhata (2009); Bussarawit & Cedhagen (2010; 2012); Phuwan et al. (2018); Trivej & Kesjinda (2018); Ninwichian et al. (2021). Geographic range. Native to Southeast Asia, with sequenced records from Pakistan, Myanmar, India, Thailand, Malaysia, Singapore, Vietnam, China, and Indonesia (Willan et al., 2021).	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B43FFA3DFB1FF03FC8BFAD5.taxon	discussion	Remarks. This is an important aquaculture species on both sides of the Gulf of Thailand, particularly on the eastern side (Bussarawit & Cedhagen, 2010; Trivej & Kesjinda, 2018). Three specimens purchased in the Samaesan seafood market were field identified as Crassostrea sp. (Table 2). M. belcheri is known as the white scar oyster because its white adductor muscle scar differentiates it from M. bilineata, the black scar oyster with its black adductor muscle scar (see below).	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B43FFA3DFA5FA8FFBD3FC08.taxon	description	(Figs. 4 A – C, 6 A, B)	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B43FFA3DFA5FA8FFBD3FC08.taxon	materials_examined	Material examined. Site 1, Sriracha; Site 6, mouth of Kungkraben Bay; Site 7, south Kungkraben Bay; Site 9, Pattaya. Magallana bilineata was also identified from the aquaculture farms in Chonburi. Published Gulf of Thailand records. Crassostrea bilineata (Röding, 1798): Nabhitabhata (2009); Bussarawit & Cedhagen (2010, 2012). Crassostrea lugubris (Sowerby II, 1871): Aungtonya et al. (1999); Murugan et al. (1999); Day et al. (2000); Trivej & Kesjinda (2018). Crassostrea iredalei Faustino, 1932: Aungtonya et al. (1999); Yoosukh & Duangdee (1999); Klinbunga et al. (2000, 2001, 2002, 2003, 2005); Yoosukh (2000); Lam & Morton (2004); Bussarawit et al. (2006); Bussarawit & Simonsen (2006 a). Geographic range. Native to Southeast Asia, with sequenced records from: India, Thailand, Malaysia, Singapore, southern Japan, and Vietnam. Unsequenced records are from Pakistan and the Philippines (Tan et al., 2024). Introduced to Queensland, Australia (Willan et al., 2021).	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B43FFA3DFA5FA8FFBD3FC08.taxon	discussion	Remarks. Magallana bilineata is known as the black scar oyster because its black adductor muscle scar differentiates it from M. belcheri, the white scar oyster, with its white adductor muscle scar. Magallana bilineata is well known in Thailand where it has been variously identified as Crassostrea bilineata, C. lugubris, and C. iredalei. Torigoe and Bussarawit (2010) clarified that there is a single species present in Thailand (C. bilineata), and C. lugubris and C. iredalei are synonyms. Identified in the field as Crassostrea sp. (Table 2). The species was introduced to aquaculture farms in the Sriracha area about 20 years ago from Kungkraben Bay and has now become naturalised in the region (Attawut Kuntavong, pers. comm.).	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B40FFA1DFFBF8CCFA34F7C2.taxon	description	Saccostrea species present in the upper Gulf of Thailand:	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B47FFA7DEDBFB1CFE6EF8E6.taxon	description	(Figs. 5 D – F, 6 C, D) Habitat. Hanging ropes, rocky shores and pier.	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B47FFA7DEDBFB1CFE6EF8E6.taxon	materials_examined	Material examined. Site 1, Sriracha; Site 3, Ta Kuan Beach; Site 6, mouth of Kungkraben Bay; Site 7, south Kungkraben Bay; Site 9, Pattaya; Site 10, Klongwan Pier; Site 13, Kao Ta Kiep. Identified in the field as Saccostrea cuccullata, S. forskahlii, and Striostrea sp. (Table 2). Saccostrea F was also identified from the aquaculture farms in Chonburi. Published Gulf of Thailand records. None. Geographic range. Taiwan and Singapore (Lam & Morton, 2006), Japan (Sekino & Yamashita, 2016), and Queensland (McDougall et al., 2024).	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B47FFA7DEDBFB1CFE6EF8E6.taxon	discussion	Remarks. Published Gulf of Thailand records as Saccostrea forskahlii (Bussarawit et al., 2006), specimen collected from Ang Sila Chonburi oyster farm.	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B47FFA4DC32FB9CFD33FF28.taxon	description	(Fig. 4 G – I) Habitat. Rocky shore.	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B47FFA4DC32FB9CFD33FF28.taxon	materials_examined	Material examined. Site 2, Samaesan. Identified in the field as Saccostrea cuccullata (Table 2). Published Gulf of Thailand records. Reported as Saccostrea mordax (Gould, 1850) by Kurozumi et al. (1989) and Yoosukh (2000). Geographic range. Australia (Western Australia to New South Wales), Japan, China, and Taiwan (Lam & Morton, 2006). Sekino & Yamashita (2013) showed a S. cucullata seq (AY 038076) collected from Thailand was actually S. mordax, but S. mordax is considered to be a synonym of S. scyphophilla (MolluscaBase eds., 2024).	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B47FFA4DC32FB9CFD33FF28.taxon	discussion	Remarks. There are numerous literature references of S. mordax on the more open Thai coastline on the Andaman Sea, but we could only find records in the Gulf of Thailand by Kurozumi et al. (1989) and Yoosukh (2000). We detected the species only on the rocky shore at Samaesan. Saccostrea mordax was originally described from Fiji. While there are GenBank sequences available for the species, there are none from the type locality. Huber (2010) discusses the taxonomic history of the species in detail. Saccostrea scyphophilla was described by Péron & Lesueur (1807) from Shark Bay, Western Australia, and Huber (2010) considers the species to be the same, with S. scyphophilla having priority. Our DNA sequences of specimens collected in Samaesan (Fig. 3) match those of Snow et al. (2023) and Wells et al. (2024), so we consider the Thai species to be S. scyphophilla.	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B47FFA7DFB1F8DCFA4EFC26.taxon	description	(Fig. 5 G – I) Habitat. Rocky shore.	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B47FFA7DFB1F8DCFA4EFC26.taxon	materials_examined	Material examined. Site 2, Samaesan. Identified in the field as Ostrea sp. (Table 2). Published Gulf of Thailand records. None. Geographic range. Uncertain, sequenced records from Queensland, Western Australia, and Japan (McDougall et al., 2024).	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
038E878C7B47FFA7DFB1F8DCFA4EFC26.taxon	discussion	Remarks. This is the species previously referred to as Saccostrea J. Sekino & Yamashita (2016), McDougall et al. (2024), and Richardson et al. (2024) all presented evidence to support their conclusion Saccostrea J is actually S. spathulata.	en	Duangdee, Teerapong, , Kitithorn Sanpanich, , Sherralee S. Lukehurst, Wells,, Fred E. (2025): Clarification of the identity of oysters in the genera Magallana and Saccostrea in the upper Gulf of Thailand based on 16 S rRNA sequences. Raffles Bulletin of Zoology 73: 12-33, DOI: 10.26107/RBZ-2025-0002
