Propeamussium sibogai ( Dautzenberg & Bavay, 1904 )

Dijkstra, H. H. & Maestrati, P., 2015, Pectinoidea (Bivalvia: Propeamussiidae and Cyclochlamydidae) from the southwestern Indian Ocean, African Invertebrates 56 (3), pp. 585-585 : 594-595

Propeamussium sibogai ( Dautzenberg & Bavay, 1904)

Fig. 1I, J

Amussium sibogai Dautzenberg & BavaY, 1904: 207 , figs 1–4; Dautzenberg & BavaY 1912: 31, pl. 28, figs 1–4. Type locality: Indonesia, Bali Sea (7°15'S 115°15'E), - 289 m, live, mud and broken shells, 14.iii.1899 ( Siboga , stn 12).

Propeamussium sibogai: Knudsen 1967: 272 , pl. 1, figs 23–24; Dijkstra 1995: 23, figs 19–22; 2001: 81; 2013: 14, pl. 1, figs 4a–d, pl. 4, fig. 4; Dijkstra & Kastoro 1997: 253, figs 24–29.; Dijkstra & Marshall 1997: 79, pl. 3, figs 1–3.; 2008: 5, figs 1, 3H–J; Wang 2002: 151, pl. 5, fig. 7; Dijkstra & Maestrati 2008: 84 ; 2013: 470.

Amussium cf. sibogai: Barnard 1969: 655 , pl. 1, figs a–d.

Description: Shell fragile, up to 65 mm in height (most specimens smaller up to 40– 50 mm), hyaline, almost circular, inequivalve, somewhat inequilateral, slightly oblique, left valve more inflated than right valve, laterallY gaping rather stronglY, auricles small and equal in size, umbonal angle 120°–125°. Left valve creamy brown, right valve creamy. Prodissoconch 220 µm high. Left valve covered with a few delicate commarginal growth lines; a few minute commarginal lamellae present near ventral margin of some specimens. Delicate radial lirae developed near posterior margin. Auricles smooth, somewhat raised on lateral margins. Right valve with widely spaced commarginal lirae, weaker at periphery, and microscopic interstitial granules. Marginal apron lacking from most specimens due to the verY thin laYer of prismatic calcite ( HaYami 1988: fig. 4). Auricles smooth. Hinge line straight. Internal costae 7 in most specimens, deep brown on left valve, white and broader on right valve. Marginal costae with 4 or 5 small nodules, visible through lateral gape. Resilifer triangular, elongate. No byssal notch.

Type material examined: Holotype (pr) ZMA Moll. 304001.

Other material examined: NW MADAGASCAR: Between Nosy-Bé and Banc du Leven (12°38'S 48°14'E), - 420–436 m, live, campaign Miriky, stn CP3183, 26.vi.2009 ( MNHN) ; Northwest region , between Nosy-Bé and Banc du Leven (12°40'S 48°12'E), - 492–524 m, live, campaign Miriky, stn CP3184, 26.vi.2009 ( MNHN) ; Northwest region , between Nosy-Bé and Banc du Leven (12°30'S 48°18'E), - 346–376 m, dead, campaign Miriky, stn CP3189, 27.vi.2009 ( MNHN) ; Northwest region , between Nosy-Bé and Banc du Leven (12°31'S 48°15'E), - 415–416 m, dead, campaign Miriky, stn CP3190, 27.vi.2009 ( MNHN) ; Northwest region , between Nosy-Bé and Banc du Leven (12°44'S 48°12'E), - 442–491 m, live, campaign Miriky, stn CP3210, 29.vi.2009 ( MNHN) ; Northwest region , between Nosy-Bé and Banc du Leven (12°33'S 47°56'E), - 391–438 m, live, campaign Miriky, stn DW3217, 30.vi.2009 ( MNHN) ; Northwest region , between Nosy-Bé and Banc du Leven (12°46'S 48°11'E), - 430–488 m, live, campaign Miriky, stn CP3223, 02.vii.2009 ( MNHN) ; Mahajamba Bay (14°50'S 46°57'E), - 340–446 m, live, campaign Miriky, stn CP3248, 07.vii.2009 ( MNHN) ; Majunga (15°22'S 46°00'E), - 493–750 m, live, campaign Miriky, stn CP3250, 08.vii.2009 ( MNHN) ; in front of Narendry Bay (14°29'S 47°26'E), - 409–425 m, live, campaign Miriky, stn CP3290, 14.vii.2009 ( MNHN) . S MADAGASCAR: Between Lokaro and Sainte Luce (24°53'S 47°28'E), - 184–203 m, dead, expedition Atimo Vatae, stn DW3515, 30.iv.2010 ( MNHN) . MOZAMBIQUE CHANNEL: Maputo transect (25°12'S 35°17'E), - 503–505 m, dead, campaign Mainbaza, stn CP3136, 10.iv.2009 ( MNHN) ; Maputo transect (23°31'S 35°50'E), - 446–475 m, live, campaign Mainbaza, stn CP3142, 11.iv.2009 ( MNHN) . MOZAMBIQUE: E of Inhaca Island , - 457 m, live, don. Mrs K. Eastwood ( NMSA 5294 , 1 pr) ; Bazaruto Island , - 549 m, live, ex colln K. Eastwood ( NMSA J5095 ) . SOUTH AFRICA: Zululand: Off Matigulu River mouth (29°22.3'S 31°57.7'E), - 400 m, dead, mud, NMDP stn ZR12, dredged RV Meiring Naudé, 16.vi.1989 ( NMSA E8820 ) . KwaZulu­Natal: Off Durban (29°55.8'S 31°13.0'E), - 337–346 m, live, stn B3.1, trawled ORI, 20.ii.2006 ( NMSA W8601 ) ; Off Durban , - 366 m, live, don. R. Kilburn, 01.ix.1969 ( NMSA 4492 ) .

Distribution and habitat: Propeamussium sibogai is recorded throughout the tropical Indo-West Pacific from southern Japan (HaYami 2000), southwards to the Philippines and Indonesia (Dautzenberg & Bavay 1912; Knudsen 1967; Dijkstra & Kastoro 1997; Dijkstra 2013), eastwards to the Solomon Islands, Vanuatu Archipelago, Loyalty Islands, New Caledonia, Wallis and Futuna Islands, Fiji, Tonga, and Kermadec Islands (Dijkstra 1995; 2001; Dijkstra & Maestrati 2008; 2013; Dijkstra & Marshall 2008), and westwards only recorded from off Durban, South Africa ( Knudsen 1967). Now also from the Mozambique Channel and northwestern and southern Madagascar (new record). Propeamussium sibogai is living on soft substrata of mud or muddy sand at a bathyal depth of - 90–750 m ( Dijkstra 2013; present records).Present material live at - 340– 750 m.

Remarks: All morphological characters of the present material are identical to the holotype from the Bali Sea, Indonesia. These characters are rather constant and can slightly vary in number of the internal ribs. Occasionally on one or both sides the lateral rib is divided into two separated ribs. The southwestern Indian Ocean morph does not have divided lateral ribs and thus only 6 internal ribs (typically 7).

Propeamussium sibogai is the type species of Luteamussium Oyama, 1951: 82 , which was treated by Hertlein (1969: N350) as a junior synonym of Propeamussium , subsequently followed in literature by most authors (see references). Descriptions of the soft parts, reproduction and diet are given by Knudsen (1967: 272).