taxonID	type	description	language	source
FE2EAC6FFFC2B048FF5B6BAA7841D97C.taxon	materials_examined	Type species: Ostrea saccellus Dujardin, 1837 (a fossil species).	en	Lukehurst, Sherralee S., Tan, Siong Kiat, Tan, Koh Siang, Dehm, Jasha, Hewavitharane, Chinthaka, Wells, Fred E. (2026): Clarifying the identities of Saccostrea scyphophilla (Péron & Lesueur, 1807) and S. mordax (Gould, 1850) (Bivalvia: Ostreidae) from the Indo-Pacific. Zootaxa 5799 (1): 1-31, DOI: 10.11646/zootaxa.5799.1.1, URL: https://doi.org/10.11646/zootaxa.5799.1.1
FE2EAC6FFFC2B048FF5B6AFB7824DE7B.taxon	description	Figs. 4 – 7 Original description: Ostrea scyphophilla Péron & Lesueur, 1807 [in Péron, 1807 – 1816]: 119. Type locality: Bernier Island (“ l’île Bernier ”), Western Australia, Australia.	en	Lukehurst, Sherralee S., Tan, Siong Kiat, Tan, Koh Siang, Dehm, Jasha, Hewavitharane, Chinthaka, Wells, Fred E. (2026): Clarifying the identities of Saccostrea scyphophilla (Péron & Lesueur, 1807) and S. mordax (Gould, 1850) (Bivalvia: Ostreidae) from the Indo-Pacific. Zootaxa 5799 (1): 1-31, DOI: 10.11646/zootaxa.5799.1.1, URL: https://doi.org/10.11646/zootaxa.5799.1.1
FE2EAC6FFFDFB052FF5B6E247E4DDB08.taxon	description	Figs. 8 C, D, 9 – 11, 12 A, B Original description: Ostrea mordax Gould, 1850: 346. Type locality: Fiji (“ Feejee Islands ”). Synonym: Saccostrea mordoides Cui et al., 2021: 70 – 71, fig. 4. Type locality: Haitang Bay, Hainan Province, China. New synonym.	en	Lukehurst, Sherralee S., Tan, Siong Kiat, Tan, Koh Siang, Dehm, Jasha, Hewavitharane, Chinthaka, Wells, Fred E. (2026): Clarifying the identities of Saccostrea scyphophilla (Péron & Lesueur, 1807) and S. mordax (Gould, 1850) (Bivalvia: Ostreidae) from the Indo-Pacific. Zootaxa 5799 (1): 1-31, DOI: 10.11646/zootaxa.5799.1.1, URL: https://doi.org/10.11646/zootaxa.5799.1.1
FE2EAC6FFFDFB052FF5B6E247E4DDB08.taxon	materials_examined	Type material: Syntypes (USNM 5958; MCZ: Mala: 178593), Fiji. Other material examined: Fiji: 19 ex. (ZRC. MOL. 32263 – 32272, ZRC. MOL. 32288 – 32297 [DNA]), USP School of Marine Studies, Suva, 18 ° 09 ' 03.0 " S 178 ° 27 ' 13.4 " E, coll. 2 October 2024; 3 ex. (ZRC. MOL. 32273 – 32274, ZRC. MOL. 32308 [DNA]), USP School of Marine Studies Jetty, Suva, 18 ° 09 ' 02.9 " S 178 ° 27 ' 15.2 " E, coll. 3 October 2024; 3 ex. (ZRC. MOL. 32275 – 32276, ZRC. MOL. 32306 [DNA]), USP School of Marine Studies Foreshore, Suva, 18 ° 09 ' 01.6 " S 178 ° 27 ' 18.6 " E, coll. 3 October 2024; 9 ex. (ZRC. MOL. 32277, ZRC. MOL. 32298 – 32305 [DNA]), USP School of Marine Studies Jetty, Suva, 18 ° 09 ' 02.9 " S 178 ° 27 ' 15.2 " E, coll. 3 October 2024; 10 ex. (ZRC. MOL. 32278 – 32281, ZRC. MOL. 32309 – 32314 [DNA]), FNU Fiji Maritime Foreshore, Suva, 18 ° 09 ' 05.6 " S 178 ° 27 ' 08.6 " E, coll. 4 October 2024; 10 ex. (ZRC. MOL. 32282 – 32287, ZRC. MOL. 31315 – 32318 [DNA]), FNU Fiji Maritime Foreshore, Suva, 18 ° 09 ' 05.8 " S 178 ° 27 ' 08.2 " E, coll. 4 October 2024. Indonesia: 1 ex. (ZRC. MOL. 35008), Tanjung Gemal, Pulau Bintan, coll. 11 May 1993. Malaysia: 6 ex. (ZRC. MOL. 35005), Tanjung Layar, Pulau Tioman, coll. 2 Jul. 1987; 3 ex. (ZRC. MOL. 32211), Pulau Babi Kechil, off Mersing, no coll. date. Philippines: 1 ex. (NHMUK 20080637), Island of Luzon, no coll. date. Singapore: 4 ex. (ZRC. 34376 [3 halves], ZRC. MOL. 34377), Pulau Salu, coll. 4 Nov. 1968; 1 ex. (ZRC. MOL. 34623), Tanjong Teritip, coll. Feb. 1969; 6 ex. (ZRC. MOL. 27639 [DNA], ZRC. MOL. 33319), Lazarus Island-Pulau Seringat, 1 ° 13.690 ' N 103 ° 50.999 ' E, coll. 20 February 2023.	en	Lukehurst, Sherralee S., Tan, Siong Kiat, Tan, Koh Siang, Dehm, Jasha, Hewavitharane, Chinthaka, Wells, Fred E. (2026): Clarifying the identities of Saccostrea scyphophilla (Péron & Lesueur, 1807) and S. mordax (Gould, 1850) (Bivalvia: Ostreidae) from the Indo-Pacific. Zootaxa 5799 (1): 1-31, DOI: 10.11646/zootaxa.5799.1.1, URL: https://doi.org/10.11646/zootaxa.5799.1.1
FE2EAC6FFFDFB052FF5B6E247E4DDB08.taxon	description	Description: Shell small to medium (c. 30 – 60 mm; SL of largest RV examined = 54.5 mm); irregularly oval (e. g., Figs. 9 A, B; 10 J – L) to slender elongate triangular (e. g., Figs. 10 G – I; 10 P – R); LV quite thick and solid, RV distinctly thinner. Shell exterior pinkish brown, usually with corroded / eroded patches of white. LV larger than RV, shallowly cupped to very deeply cupped; posterior side often thicker and prominently raised from the attached substate in shallowly cupped specimens, or boxy with entirely margin strongly raised in deeply cupped ones (e. g., 10 J; 10 M). RV exterior surface with several broad radial ribs; often corroded / eroded especially around the centre with or without dark brown bands and lines of the conchiolin layers, usually rimmed with a pinkish brown border. Shell margin scalloped, often strongly undulating with prominent lobes. Shell interior white with pink tint, LV usually with darker cloudy patches, occasionally with dark greenish brown spots and blotches; RV usually with pinkish brown to dark chocolate brown blotches and bands; interior margin pinkish brown, usually with prominent chocolate brown line or band, ranging from being present only near the hinge (e. g., Figs. 10 O; 10 R) to around the entire margin of the RV (e. g., 10 C). Umbonal cavity deep. Chomata usually prominent around entire margin, sometimes indistinct or absent along the ventral edge (e. g., Fig. 10 O). Adductor muscle scar of LV usually white (e. g., Figs. 10 D; 10 G), rarely stained brown (e. g., Fig. 10 J); RV usually dark brown to black (e. g., Fig. 9 C; 10 C), occasionally white streaked with brown lines and / or bands (e. g., Fig. 10 I; 11 C), often strongly raised, sometimes ridge-like, on ventral part (see Fig. 12 A, B). Habitat: In Laucala Bay, Fiji, S. mordax inhabits both natural rock substrates and artificial structures, thriving particularly on concrete surfaces such as seawalls, jetties, pylons, and pontoons in intertidal zones. Published distribution based on DNA analyses: Okinawa, Japan (Sekino & Yamashita 2013; Hamaguchi et al. 2014 as S. mordax - C), Hainan province, China (Cui et al. 2021 as S. mordoides), Guangdong province, China (Zhang et al. 2025), Queensland, Australia (McDougall et al. 2024; Richardson et al. 2024), Singapore (this study, GenBank PV 760218) and Indonesia (Zhang et al. 2025). Other records not based on DNA sequences: Indonesia: Pulau Bintan, Riau (this study); Malaysia: Pulau Tioman (this study); Pulau Babi Kechil (this study); Philippines: Luzon (this study).	en	Lukehurst, Sherralee S., Tan, Siong Kiat, Tan, Koh Siang, Dehm, Jasha, Hewavitharane, Chinthaka, Wells, Fred E. (2026): Clarifying the identities of Saccostrea scyphophilla (Péron & Lesueur, 1807) and S. mordax (Gould, 1850) (Bivalvia: Ostreidae) from the Indo-Pacific. Zootaxa 5799 (1): 1-31, DOI: 10.11646/zootaxa.5799.1.1, URL: https://doi.org/10.11646/zootaxa.5799.1.1
FE2EAC6FFFDFB052FF5B6E247E4DDB08.taxon	discussion	Remarks: Saccostrea mordax can be distinguished from S. scyphophilla based solely on their shell morphology. Compared to S. scyphophilla, S. mordax is generally smaller, and has a distinctive pink shell margin, which is usually more highly scalloped with fewer protruding lobes. The interior of the valves tends to be more distinctively pinkish brown, often featuring chocolate brown bands and blotches especially along the anterior and posterior margins. The often brown adductor muscle scar on the RV is typically raised, either a bump or only along its ventral side, compared to that of S. scyphophilla which is usually not as prominently raised (Fig. 12). Our study has also provided evidence that topotypes of S. mordax from Fiji are genetically and morphologically indistinguishable from the recently described S. mordoides from China and hence suggest that the two species are synonymous.	en	Lukehurst, Sherralee S., Tan, Siong Kiat, Tan, Koh Siang, Dehm, Jasha, Hewavitharane, Chinthaka, Wells, Fred E. (2026): Clarifying the identities of Saccostrea scyphophilla (Péron & Lesueur, 1807) and S. mordax (Gould, 1850) (Bivalvia: Ostreidae) from the Indo-Pacific. Zootaxa 5799 (1): 1-31, DOI: 10.11646/zootaxa.5799.1.1, URL: https://doi.org/10.11646/zootaxa.5799.1.1
