Alvania letourneuxi, Amati & Giulio & Oliverio, 2023

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 : 809-811

Alvania letourneuxi n. sp.

( Figs 5 ; 6 ; 49A ; 53A ; Tables 1 ; 2 )

urn:lsid:zoobank.org:act:A14FC6C0-1612-4047-9680-667661FE88A5

TYPE MATERIAL. — Holotype. Tuamotu • dd (height 1.60 mm, width 0.95 mm, Figs 5 ; 6 ; 49A ); Makemo , Passe Arikitamiro ; 16°37’15”S, 143°33’50”W; 1-20 m; J. Letourneux leg.; MNHN-IM-2000-38703 .

TYPE LOCALITY. — Tuamotu: Makemo, Passe Arikitamiro; 16°37’15”S, 143°33’50”W; 1- 20 m.

DISTRIBUTION AND SYMPATRY. — Alvania letourneuxi n. sp. is known from the South Pacific Ocean, in the Tuamotu Archipelago (Makemo) ( Fig. 49A ).

Alvania letourneuxi n. sp. is sympatric with Alvania parvimaculata n. sp. in the Tuamotu (Makemo) .

ETYMOLOGY. — Named after Jean Letourneux (Mahina, Tahiti), who collected the type material in the Tuamotu, for his continuous study of the Polynesian molluscs, and for having made materials from his collection available for this revision.

DIAGNOSIS. — Alvania with small shell (<2 mm height); protoconch paucispiral; spiral sculpture a little stronger than axial; two spiral cordlets starting after protoconch-teleoconch boundary; colouration uniform white.

DESCRIPTION OF HOLOTYPE

Shell ( Figs 5 A-C; 6A; 53A)

Small for the genus, height 1.60 mm, width 0.95 mm, height/ width ratio 1.69, robust, ovate-conical.

Protoconch ( Figs 5D, E ; 6 B-D)

Paucispiral with nucleus intorted, of 1 convex whorl, height 0.250 mm, nucleus diameter 0.075 mm, first half whorl diameter 0.150 mm, maximum diameter 0.200 mm; with 5 small keels, interspaced by axial riblets, replaced by scattered on the last quarter of whorl. Protoconch-teleoconch boundary well marked, prosocline.

Teleoconch

Of 2.90 convex whorls, with suture impressed. Axial sculpture on the last whorl of 21 slightly prosocline ribs thinner than interspaces, gradually vanishing at the base. Spiral sculpture of equidistant cordlets slightly broader than axials, 7 on the last whorl, 3 above the aperture, one on suture line and 3 on the base. Cordlets II and III starting immediately after the protoconch-teleoconch boundary; cordlet I (subsutural) thinner, starting subsequently. Medium size, rounded tubercles at the intersections; interspaces quadrangular. Microsculpture of weak, minute spiral threads crossing the growth lines ( Fig. 6B ). Umbilical fissure absent. Aperture piriform, height 0.92 mm, height/aperture height ratio 1.74, peristome continuous and simple, external varix moderately thickened, outer lip sharp, smooth internally, prosocline.

Colour

Colouration uniform white.

Operculum and soft parts

Unknown.

VARIABILITY

A single specimen known. (See Table 1 and Appendix 1).

REMARK

See under A. parvimaculata n. sp. for detailed comparison.

Figures

FIG. 5. — Alvania letourneuxi n. sp.: holotype, Tuamotu, Makemo, Passe Arikitamiro 1-20 m, MNHN-IM-2000-38703, height 1.60 mm: A-C, shell; D, E, details of the protoconch. Scale bars: D, E, 20 μm.

FIG. 6. — Alvania letourneuxi n. sp.: holotype, Tuamotu, Makemo, Passe Arikitamiro 1-20 m, MNHN-IM-2000-38703, height 1.60 mm: A, shell; B-D, detail of the protoconch sculpture. Scale bars: B, C, 100 μm; D, 20 μm.

FIG. 49. — Type locality of Alvania isolata (Laseron, 1956) (○, Christmas Island), and location of the stations of the “Valdivia” deep-water expedition (●) where types of Alvania denseclathrata (Thiele, 1925) (Stns 81, 95 and 104) and of Alvania proditoris (Thiele, 1925) n. comb. (Stns 81, 95 and 101) were collected.

FIG. 53. — Alvania Risso,1826,Ellenstrongia n. gen., Haurakia Iredale,1915,Parashiela Laseron,1956,Simulamerelina Ponder,1985 and Substea Cotton,1944:A, Alvania letouneuxi n.sp., holotype,MNHN-IM-2000 38703, height 1.60 mm; B, Alvania herosae n. sp., holotype,MNHN-IM-2000-38704, height 2.02 mm;C, Alvania herosae n.sp.(morph B),MNHN,height 2.16 mm;D, Alvania parvimaculata n. sp.,holotype,MNHN-IM-2000-38706, height 1.65 mm;E, Alvania prosocostata n.sp., holotype, MNHN-IM-2000-38708 height 2.05 mm; F, Alvania uapou n. sp., holotype, MNHN-IM-2000-38710, height 1.70 mm; G, Ellenstrongia tarasoc n. gen., n. sp., holotype,MNHN-IM-2000-39448, height 4.50 mm; H, Haurakia marmorata (Hedley, 1907), Society Islands,height 1.95 mm, coll. JL; I, Parashiela ambulata Laseron, 1956, Australes: Rapa Pointe Kauira, height 1.60 mm, MNHN; J, Parashiela expansilabrum n. sp. holotype, MNHN-IM-2000-38712 height 1.47 mm; K, Parashiela obesula n. sp. holotype, MNHN-IM-2000-38714, height 1.32 mm; L, Parashiela rimatara n. sp. holotype, MNHN-IM-2000-38716, height 1.47 mm; M, Parashiela rotundata n. sp. holotype, MNHN-IM-200038718-, height 1.10 mm; N, Parashiela soniae n. sp., holotype, MNHN-IM-2000-38720, height 1.17 mm; O, Simulamerelina australes n. sp. holotype, MNHN-IM-2000-38722, height 2.47 mm; P, Simulamerelina densestriata n. sp., holotype, MNHN-IM-2000-38724, height 2.45 mm; Q, Simulamerelina gracilis n. sp., holotype, MNHN-IM-2000-38726, height 2.45 mm; R, Simulamerelina lepteseiras n. sp., holotype, MNHN- IM-2000-38727, height 1.47 mm; S, Simulamerelina micrometrica n. sp., holotype, MNHN-IM-2000-38728, height 1.33 mm; T, Simulamerelina tuamotu n. sp. holotype, MNHN-IM-2000-38730, height 1.57 mm; U, Subestea moruroa n. sp., holotype, MNHN-IM-2000-38732, height 1.96 mm.