Similipecten eous, : Oliver, 1992

Dijkstra, H. H. & Maestrati, P., 2015, Pectinoidea (Bivalvia: Propeamussiidae and Cyclochlamydidae) from the southwestern Indian Ocean, African Invertebrates 56 (3), pp. 585-585 : 620-622

Similipecten eous (Melvill in Melvill & Standen, 1907)

Fig. 8G–H

Pecten eous Melvill in Melvill & Standen, 1907: 808, pl. 55, fig. 9. TYpe localitY: Gulf of Oman (24°58'N 56°54'E), - 285 m, shell-sand.

Similipecten eous: Oliver 1992: 74 , text-figs 9a–b; Bosch, Dance, Moolenbeek & Oliver 1995: 232; Dijkstra & Knudsen 1998: 50, pl. 3, figs 10–11; Dijkstra 2013: 22, pl. 3, figs 3a–d, 4a–c; Dijkstra & Janssen 2013: 199, figs 50–51.

Description: Shell small, up to 4.1 mm in height, fragile, almost circular, translucent or opaque milky-whitish or creamy, inequivalve, subequilateral, right valve more convex than left one. Prodissoconch 200 µm long. Left valve smooth, some specimens with minute commarginal lirae near the ventral margin. Right valve also smooth, with a microscopic granular structure. Anterior auricles with commarginal lamellae or lirae, more prominent near side of disc, posterior auricles smooth and continuous with disc. Internal riblets and ctenolium are lacking. Byssal notch small.

Type material examined: Lectotype NHMUK 1907.5.3.18, designated by Dijkstra & Knudsen (1998: 50); 2 paralectotypes NHMUK 1907.5.3.19-20, 17 paralectotypes NMW 1955.158.673. Several paralectotypes deposited in other museums (Dijkstra, personal observation).

Other material examined: MOZAMBIQUE CHANNEL: Maputo transect (25°11'S 35°02'E), - 101–102 m, dead, campaign Mainbaza, stn CP3132, 10.iv.2009 ( MNHN) ; Maputo transect (25°53'S 23°07'E), - 112– 127 m, live, campaign Mainbaza, stn CP3130, 09.iv.2009 ( MNHN) . MOZAMBIQUE: Inhaca Island: In front of Ponta Malengane (26°03.6'S 33°01.8'E), - 75 m, dead, expedition Inhaca 2011, stn MD26, 05.xii.2011 ( MNHN) . Maputo: offshore (25°55'S 33°07'E), - 140–160 m, dead, s/n, dredge, leg. J. Rosado, xi.2011 ( MNHN) . S MADAGASCAR: E of Faux Cap (25°38'S 46°13'E), - 128–133 m, dead, expedition Atimo Vatae, stn CP3561, RV Nosy Bé 11, 06.v.2010 ( MNHN) ; S Pointe Barrow (25°30'S 44°16'E), - 209–229 m, dead, expedition Atimo Vatae, stn DW3581, RV Nosy Bé 11, 10.v.2010 ( MNHN) ; SE Pointe Barrow (25°28'S 44°25'E), - 203–210 m, dead, expedition Atimo Vatae, stn CP3584, RV Nosy Bé 11, 10.v.2010 ( MNHN) ; SE Pointe Barrow (25°03'S 44°00'E), - 113–135 m, dead, expedition Atimo Vatae, stn DW3588, RV Nosy

Bé 11, 11.v.2010 ( MNHN). SOUTH AFRICA: KwaZulu­Natal: Off Umlaas Canal (29°58.5'S 31°00.8'E), - 75 m, dead, muddy sand, NMDP stn XX77, dredged RV Meiring Naudé , 10.vii.1985 ( NMSA D4899 ) .

Distribution and habitat: Red Sea, Gulf of Oman, Arabian Sea, Persian Gulf, Indonesia and Philippines ( Dijkstra & Knudsen 1998: 51; Dijkstra 2013: 22). Now also Mozambique Channel, southern Madagascar and northeastern South Africa (new record). Living sublittorally to upper bathyally (- 97–410 m, Dijkstra 2013: 22) on soft substrata (mud, muddy sand, shell grit). Present material live at - 112– 127 m.

Remarks: The present specimens from the Mozambique Channel and southern Madagascar are morphologically similar to the type material from the Gulf of Oman. A closely resembling species, Similipecten similis ( Laskey, 1811) from the eastern Atlantic, is larger in size (up to 8 mm in height) and more brightly coloured, rarely with some rudimentary interior riblets.These are lacking in S. eous . For comparison with Similipecten herosae Dijkstra & Maestrati, 2008 from Tonga, see Dijkstra and Maestrati (2008: 101).

Figures

Fig. 8. Cyclochlamys bacachorda sp. n., holotype: South Africa, off Nthlonyane River, (A) external view of the left valve, H = 3 mm, scale bar = 1 mm; (B) external view of the right valve, H =, scale bar = 1 mm; (D) prodissoconch of the left valve, H = 3 mm, scale bar = 0.1 mm; (E) details of the left valve, H = 3 mm, scale bar = 0.1 mm; (F) details of the right valve, H = 3 mm, scale bar = 0.1 mm (NMSA E55/T4029); paratype, (C) external view of the right valve, H = 2.2 mm, scale bar = 0.5 mm (NMSA P0325/T4030). (G–H) Similipecten eous (Melvill in Melvill & Standen, 1907): campaign Mainbaza, stn CP3132, (H) external view of a left valve, H = 2.6 mm, scale bar = 1 mm; (H) details of a left valve, H = 2.6 mm, scale bar = 0.1 mm (MNHN).