Alvania letourneuxi Amati & Giulio & Oliverio 2023, n. sp.
Creators: name: Amati, Bruno
name: Giulio, Andrea Di
name: Oliverio, Marco
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Rissoidae
Alvania
Alvania letourneuxi

description: 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.
description: Published as part of 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, pp. 803-892 in Zoosystema 45 (25) on pages 809-811, DOI: 10.5252/zoosystema2023v45a25, http://zenodo.org/record/10458066