Alvania isolata ( Laseron, 1956 )

Amati, Bruno, Giulio, Andrea Di & Oliverio, Marco, 2023, Shallow-water Rissoidae of the genera Alvania Risso 1826 Haurakia Iredale 1915 Parashiela Laseron 1956 Simulamerelina Ponder 1985 and Subestea Cotton 1944 Gastropoda Caenogastropoda Rissooidea from French Polynesia with the description of a new deep-water genus, Zoosystema 45 (25), pp. 803-892 : 808-809

Alvania isolata ( Laseron, 1956)

( Figs 4 ; 48 )

Haurakia isolata Laseron, 1956: 439 , fig. 144.

Alvania isolata – Ponder 1985: 142, figs 93A, B.

TYPE MATERIAL. — Holotype. Australia • dd (height 1.5 mm, Fig. 4A, B ); Christmas Island ; AMS C.102476.

Paratypes. Australia • dd (height 1.6 mm, Fig. 4 D-F); Christmas Island ; AMS C.102476 • 7 dd (one of these height 1.6 mm, Fig. 4G, H ); Christmas Island ; AMS C.304689 .

TYPE LOCALITY. — Christmas Island ( Australia).

DISTRIBUTION. — Only known from the type locality, in the eastern Indian Ocean ( Fig. 48 ).

DIAGNOSIS. — Alvania with small (height <2 mm) and robust shell, ovate-conical shape; with double sculpture (axial and spiral) of equal thickness, aperture piriform, continuous and simple peristome, outer lip with mediocre varix and devoid of umbilical fissure. Protoconch paucispiral, dome-shaped sculptured of 4-5 smooth spiral cordlets. Colouration whitish, with series of pairs of short brown lines.

REMARKS

Besides Laseron (1956) and Ponder (1985), some authors have used the name Alvania isolata ( Laseron, 1956) for three similar, yet distinct and probably all undescribed species. One from Hawaii ( Kay 1979: 78, fig. 27C; Severns 2011: 114, pl. 41, fig. 1) with finely striated protoconch, teleoconch with angled whorls, and three sets of red-orange subsutural lines; another from Taiwan ( Chang & Wu 2004: 10, 11, 71, fig. 5) and the Philippines ( Hasegawa 2006b: 107, fig. 2), also with finely striated protoconch with more convex whorls, and teleoconch with broader base. Finally, Alvania isolata has also been reported from French Polynesia ( Tröndlé & Boutet 2009; Salvat & Tröndlé 2017). The latter records actually refer to a further undescribed species (see below Alvania uapou n. sp.).

Figures

FIG. 4. — Alvania isolata (Laseron, 1956): A, B, holotype, height 1.5 mm, Christmas Island, AMS C.102476; C, original drawing; D-F, paratype, height 1.6 mm, Christmas Island, AMS C.102476; G, H, paratype, height 1.6 mm, Christmas Island, AMS C.304689. Images: A. C. Miller; copyright: Australian Museum. Scale bar: 100 mm.

FIG. 48. — Distribution maps of the Polynesian species of Alvania Risso, 1826 and Ellenstrongia n. gen.: A, Alvania letourneuxi n. sp. (●) and Alvania herosae n. sp. (○); B, Alvania parvimaculata n. sp. (○) and Alvania prosocostata n. sp. (●); C, Alvania uapou n. sp.; D, Ellenstrongia tarasoc n. gen., n. sp.