Parvamussium siebenrocki ( Sturany, 1901 )

Dijkstra, H. H. & Maestrati, P., 2015, Pectinoidea (Bivalvia: Propeamussiidae and Cyclochlamydidae) from the southwestern Indian Ocean, African Invertebrates 56 (3), pp. 585-585 : 606-608

Parvamussium siebenrocki ( Sturany, 1901)

Fig. 4D–F

Amussium siebenrocki SturanY, 1901: 269, pl. 4, figs 5–8. TYpe localitY: Red Sea , near Shadwan Island (27°25'N 34°30'E), - 1082 m, yellowish muddy sand, 02.iv.1896 ( Pola I, stn 72) .

Propeamussium (Parvamussium) siebenrocki: Oliver 1992: 70 , 73, pl. 12, figs 3a–3b, text-figs 7a–b.

Parvamussium siebenrocki: Bosch, Dance, Moolenbeek & Oliver 1995: 232 , fig. 1011; Dijkstra & Knudsen 1998: 46, pl. 1, figs 1–4; Dijkstra & Janssen 2013: 194, figs 23–25, 36–37, 43–45.

Description: Shell up to 9.1 mm in height, fragile, subcircular, inequivalve, nearly equilateral, right valve slightly more convex than left valve, auricles unequal, umbonal angle 110°, colour of left valve creamy with milky-white, orange or brown dots, right valve more uniformly whitish. Prodissoconch 200 µm long. Left valve sculptured with irregularly spaced and developed radial riblets and weak commarginal lamellae (most specimens), also almost smooth, lacking commarginal and most of radial sculpture in central disc area and rudimentary laterally (some specimens). Preradial stage only with fine commarginal lamellae. Anterior auricle with fine commarginal lamellae, posterior same sculpture, but more delicate. Right valve with regularly spaced commarginal lamellae. Anterior auricle with some small radial riblets near the byssal fasciole, and commarginal lamellae, prominent near dorsal margin. Posterior auricle only sculptured with commarginal lamellae. Internal ribs 7–10 (usually 9–10), sometimes with a few rudimentary interstitial riblets.

Type material examined: Lectotype (pr) NHMW 84.355, selected by Dijkstra & Janssen (2013: 194, pl. 4, figs 5–8); paralectotYpes, NHMW 84.177.

Other material examined: NW MADAGASCAR: West of Cap d’Ambre (12°08'S 48°56'E), - 238–249 m, dead, campaign Miriky, stn DW3196, 28.vi.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) ; Manantenina (24°23'S 47°32'E), - 154–168 m, dead, expedition Atimo Vatae, stn DW3522, 01.v.2010 ( MNHN) ; Manantenina (24°23'S 47°31'E), - 200–220 m, dead, expedition Atimo Vatae, stn DW3523, 01.v.2010 ( MNHN) ; Manantenina (24°23'S 47°32'E), - 307–319 m, dead, expedition Atimo Vatae, stn DW3524, 01.v.2010 ( MNHN) ; Sainte Luce (24°43'S 47°32'E), - 296–307 m, dead, expedition Atimo Vatae, stn DW3534, 02.v.2010 ( MNHN) ; S Pointe Barrow (25°30'S 44°16'E), - 209–229 m, dead, expedition Atimo Vatae, stn DW3581, 10.v.2010 ( MNHN) ; S Pointe Barrow (25°31'S 44°16'E), - 296–302 m, dead, expedition Atimo Vatae, stn CP3583, 10.v.2010 ( MNHN) ; SE Pointe Barrow (25°28'S 44°25'E), - 203–210 m, dead, expedition Atimo Vatae, stn CP3584, 10.v.2010 ( MNHN) ; SE Pointe Barrow (25°03'S 44°00'E), - 113–135 m, dead, expedition Atimo Vatae, stn DW3588, 11.v.2010 ( MNHN) ; SW Pointe Barrow (25°03'S 44°00'E), - 132–153 m, dead, expedition Atimo Vatae, stn CP3589, 11.v.2010 ( MNHN) ; Lavanono (25°45'S 44°29'E), - 122–123 m, dead, expedition Atimo Vatae, stn DW3599, 12.v.2010 ( MNHN) ; S Cap Sainte Marie (26°13'S 45°08'E), - 250–300 m, dead, expedition Atimo Vatae, stn CP3614, 14.v.2010 ( MNHN) . MOZAMBIQUE CHANNEL: Inhambane transect (23°59'S 35°39'E), - 206–210 m, live, campaign Mainbaza, stn CC3160, 15.iv.2009 ( MNHN) ; Maputo transect (25°53'S 33°07'E), - 112–127 m, dead, campaign Mainbaza, stn CP3130, 09.iv.2009 ( MNHN) ; Maputo transect (25°11'S 35°02'E), - 101–102 m, dead, campaign Mainbaza, stn CP3132, 10.iv.2009 ( MNHN) ; Maputo transect (25°11'S 35°10'E), - 200–201 m, dead, campaign Mainbaza, stn CP3133, 10.iv.2009 ( MNHN) ; Maputo transect (23°33'S 35°41'E), - 171–180 m, dead, campaign Mainbaza, stn CP3144, 11.iv.2009 ( MNHN) ; Zambeze transect (19°31'S 36°46'E), - 261–264 m, live, campaign Mainbaza, stn CC3150, 13.iv.2009 ( MNHN) ; Zambeze transect (19°34'S 36°45'E), - 352– 357 m, dead, campaign Mainbaza, stn CC3151, 13.iv.2009 ( MNHN) ; Inhambane transect (23°55'S 35°37'E), - 148–152 m, live, campaign Mainbaza, stn CC3159, 15.iv.2009 ( MNHN) . MOZAMBIQUE: Inhaca Island: In front of Ponta Malengane (26°03.6'S 33°03.8'E), - 130 m, dead, expedition Inhaca 2011, stn MD27, 05.xii.2011 ( MNHN) ; NE Ponta do Farol (25°54.8'S 33°06.6'E), - 145 m, live, expedition Inhaca 2011, stn MD28, 05.xii.2011 ( MNHN) ; SW Ilha dos Portugueses (25°59.7'S 32°54.2'E), - 8 m, dead, expedition Inhaca 2011, stn MS12, 05.xii.2011 ( MNHN) . SOUTH AFRICA: Zululand: Off du Leven Point (27°55.0'S 32°38.8'E), - 250 m, dead, NMDP stn ZL5, dredged RV Meiring Naudé, 09.vi.1988 ( NMSA E3564 and S9362) ; SE of Neill Peak ( Cunge ) (28°43.0'S 32°21.7'E), - 110–115 m, dead, mud, stones, NMDP stn ZP2, dredged RV Meiring Naudé, 12.vi.1988 ( NMSA E3813 ) . KwaZulu­Natal: SE of Sheffield Beach (29°30.3'S 31°45.7'E), - 100–105 m, dead, glutinous grey mud, NMDP stn XX139, dredged RV Meiring Naudé, 14.vi.1988 ( NMSA E5057 ) ; Off Tongaat Bluff (29°43.8'S 31°26.7'E), - 240 m, dead, fine, soft mud, NMDP stn ZV1, dredged RV Meiring Naudé, 20.vi.1989 ( NMSA E9907 ) ; Off Durban (29°53.2'S 31°11.2'E), - 165 m, dead, fine muddy sand, corals, NMDP stn XX14, dredged RV Meiring Naudé, 16.vi.1983 ( NMSA B5895 ) . KwaZulu­Natal: Off Umlaas Canal (30°00.8'S 31°02.6'E, - 100 m, dead, coarse sand, NMDP stn XX73, dredged RV Meiring Naudé, 10.vii.1985 ( NMSA D1207 ) ; KwaZulu­Natal: Off Port Edward (31°06.4'S 30°18.0'E), - 125 m, dead, living sponges, NMDP stn XX58, dredged RV Meiring Naudé, 08.vii.1985 ( NMSA D917 ) . Off Amanzimtoti (30°05.0'S 31°00.4'E), - 100 m, dead, medium sand, NMDP stn XX60, dredged RV Meiring Naudé, 08.vii.1985 ( NMSA D1472 ) ; Off Park Rynie , - 136 m, dead, sponge rubble, dredged by R. Kilburn, 05.iii.1981 ( NMSA B3891 ) ; Off Park Rynie , - 100 m, dead, sand, sponge rubble, dredged by R. Kilburn, 04.iii.1981 ( NMSA B3574 ) ; Off Park Rynie , - 110–130 m, dead, eroded shell & conglomerate, dredged by R. Kilburn, 02.iii.1981 ( NMSA B3563 ) ; Off Umzinto (30°21.6'S 30°51.0'E), - 84 m, dead, NMDP stn X2, dredged RV Meiring Naudé, 15.vii.1982 ( NMSA E103 ) . Transkei: between Mtamvuna and Mzamba River (31°05.6'S 30°18.6'E), - 100 m, dead, large living sponges, rubble, NMDP stn XX6, dredged RV Meiring Naudé, 15.vi.1983 ( NMSA C5436 ) . Transkei: Off Port Grosvenor (29°57.6'S 31°26.2'E), - 100–115 m, dead, sand, some mud, solitary coral, shells, NMDP stn D3, dredged RV Meiring Naudé, viii.1981 ( NMSA C1347 ) . Transkei: Off Port Grosvenor (31°25.6'S 29°58.0'E), - 95–100 m, dead, coarse sand, very few gorgonians, NMDP stn D12, dredged RV Meiring Naudé, viii.1981 ( NMSA C588 ) ; Off Whale Rock (31°58.8'S 29°16.8'E), - 90 m, dead, sponge rubble, coarse sand, some rocks, NMDP stn M12, dredged RV Meiring Naudé, 03.vii.1985 ( NMSA C9442 ) ; Off Whale Rock (32°01.7'S 29°18.2'E), - 150–165 m, dead, coarse sand, discoid corals, NMDP stn M9, dredged RV Meiring Naudé, 20.vii.1982 ( NMSA C2344 ) ; Off Bulungula River mouth (32°09.8'S 29°04.6'E), - 90 m, dead, slightly muddy sand, NMDP stn O1, dredged RV Meiring Naudé, 17.vii.1982 ( NMSA C2627 ) ; Off Nthlonyane River (32°15.4'S 29°00.8'E), - 90–95 m, dead, lithothamnion pebbles, NMDP stn P5, dredged RV Meiring Naudé, 17.vii.1982 ( NMSA C2555 ) ; Off Qora River (32°33.4'S 28°48.0'E), - 100 m, dead, coarse sand, some sponge rubble, NMDP stn U6, dredged RV Meiring Naudé, 14.vi.1983 ( NMSA C4858 ) ; Off Qora River (32°34.0'S 28°49.7'E), - 400–420 m, dead, coarse slightly muddy sand, NMDP stn U13, dredged RV Meiring Naudé, 12.vii.1984 ( NMSA C6861 ) ; Off Sandy Point (32°37.4'S 28°36.9'E), - 90 m, dead, calcareous debris, coarse sand, NMDP stn W1, dredged RV Meiring Naudé, 11.vi.1983 ( NMSA C4533 , 1 lv, 3 rv) ; Off Qolora River (32°41.4'S 28°30.0'E), - 80 m, dead, coarse sand, NMDP stn Y5, dredged RV Meiring Naudé, 13.vi.1983 ( NMSA C3954 ) ; Off Sandy Point (32°42.9'S 28°48.6'E), - 350 m, dead, coarse sand, broken shell, NMDP stn W14, dredged RV Meiring Naudé, 14.vii.1984 ( NMSA C6783 ) ; Off Qolora River (32°46.2'S 28°37.5'E), - 440–446 m, dead, fine sand, branching coral, NMDP stn Y1, dredged RV Meiring Naudé, 12.vi.1983 ( NMSA C4067 ) ; Off Kei River (32°49.3'S 28°31.2'E), - 138 m, dead, coarse sand, NMDP stn Z4, dredged RV Meiring Naudé, 13.vi.1983 ( NMSA C5085 ) .

Distribution and habitat: Red Sea, Gulf of Aden, Arabian Sea, Persian Gulf, southwards to eastern South Africa. Living upper bathyally on soft substrata (mixture sediments of mud and sand). Present specimens live at - 145–261 m (minimum depth range).

Remarks: Parvamussium cristatellum (Dautzenberg & Bavay, 1912) recorded from the northern Indian Ocean, western, southwestern, and southern Pacific (Dijkstra & Maestrati 2012: 392) is morphologically very close to the present species. Parvamussium cristatellum differs somewhat in having a more prominent radial sculpture on the left valve, but other characters are similar.

Figures

Fig. 4. Parvamussium spp.: (A–C) P. scitulum (E.A. Smith, 1885): campaign Mainbaza, stn CP3130, (A) external view of the left valve, H = 6.2 mm, scale bar = 2 mm; (B) external view of the right valve, H = 5.7 mm, scale bar = 2 mm; (C) details of the left valve, H = 6.2 mm, scale bar = 0.1 mm (MNHN). (D–F) P.siebenrocki (Sturany,1901):campaign Mainbaza, stn CC3160, (D) external view of the left valve, H = 6.9 mm, scale bar = 2 mm; (E) external view of the right valve, H = 5.9 mm, scale bar = 2 mm; (F) details of the left valve, H = 6.9 mm, scale bar = 0.1 mm (MNHN). (G–M) P. strongae sp. n., holotype: campaign Miriky, stn DW3212, (G) external view of the left valve, H = 21.9 mm, scale bar = 1 cm; (H) internal view of the left valve, H = 21.9 mm, scale bar = 1 cm; (I) external view of the right valve, H = 17.4 mm, scale bar = 1 cm; (J) internal view of the right valve, H = 17.4 mm, scale bar = 1 cm; (K) prodissoconch of the left valve, H = 21.9 mm, scale bar = 0.2 mm; (L) details of the left valve, H = 21.9 mm, scale bar = 0.1 mm; (M) details of the right valve, H = 17.4 mm, scale bar = 0.1 mm (MNHN 39087).