Simulamerelina lepteseiras, 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 : 864

Simulamerelina lepteseiras n. sp.

( Figs 41 ; 52B ; 53R ; Tables 7 ; 8 ; 9 )

urn:lsid:zoobank.org:act:7E3425DF-8342-4367-A382-AB0FA931D123

TYPE MATERIAL. — Holotype. Tuamotu • dd (height 1.47 mm, width 0.88 mm, Figs 41 ; 53R ); Moruroa ; 21°46’37”S, 138°53’31”W; beached; on the sea-line; MNHN-IM-2000-38727 .

TYPE LOCALITY. — Tuamotu. Moruroa, 21°46’37”S, 138°53’31”W; on the sea-line.

OTHER MATERIAL EXAMINED. — Tuamotu • 1 dd (photograph only); Ana’a, Tukuhora; 17°20’41”S, 145°31’26”W; 1-2 m; lagoon; coll. JL • 1 dd (photograph only); Rangiroa, Tiputa; 14°58’15”S, 147°37’33”W; beached; coll. JL.

Gambier • 1 dd (photograph only);Totegegi; 23°5’2”S, 134°52’58”W; 1-2 m; beached sediment; coll. JL.

DISTRIBUTION AND SYMPATRY. — Simulamerelina lepteseiras n. sp. is known from the South Pacific Ocean in the Tuamotu (Moruroa, Rangiroa, Ana’a) and Gambier ( Fig. 52B ).

S. lepteseiras n. sp. is sympatric with S. australes n. sp. and S. gracilis n. sp. in the Tuamotu (Moruroa) ( Table 9 ).

ETYMOLOGY. — For the thin basal cords, from the Greek ΛΕΠΤά (meaning thin), and σΕΙΡάς (meaning cords).

DIAGNOSIS. — Simulamerelina with small shell for the genus (<1.50 mm), pupoid, moderately robust. Protoconch paucispiral. Teleoconch with axial and spiral sculpture of the same strength. Axial ribs interrupted before reaching the base. Nine spiral cordlets on last whorl, four above the aperture, the second cordlet strongest, acute. Entire surface covered by dense evenly spaced spiral threads. Start of 3 spiral cordlets after protoconch-teleoconch boundary. Colouration uniform white.

DESCRIPTION OF HOLOTYPE

Shell ( Figs 41 A-C, F; 53R)

Small for the genus, height 1.47 mm, width 0.88 mm height/ width ratio 1.67, elongate ovate.

Protoconch ( Fig. 41D, E, G )

Paucispiral with barely twisted nucleus, of 1.35 convex whorls, height 0.237 mm, nucleus diameter 0.087 mm, first half whorl diameter 0.175 mm, maximum diameter 0.275 mm. Sculpture of one adapical spiral keel, and sparse microgranules on the whole surface. Protoconch-teleoconch boundary well marked.

Teleoconch

Of 2.9 convex whorls, suture scarcely impressed. Axial sculpture on the last whorl of 12 orthocline or slightly opisthocline ribs, thinner than the interspaces and sharply interrupted before reaching the base. Spiral sculpture of 9 equidistant spiral cordlets on the last whorl, 4 above the aperture, of same strength as axials, cordlet II acute; cordlets II, III, IV starting immediately after protoconch-teleoconch boundary.Subsutural cordlet I very weak, gradually forming after one whorl. Basal cordlets weaker and with wide interspaces. Microsculpture ( Fig. 41H ) of dense spiral threads, more marked and spaced in the interspaces. Umbilical fissure absent. Aperture oval, height 0.65 mm, height/aperture height ratio 2.26, peristome duplicated, outer lip broad, internally smooth, externally thickened by a strong opisthocline and flexuose varix.

Colour

Colouration uniform white.

Operculum and soft parts

Unknown.

VARIABILITY

Minimum and maximum dimensions: height 1.4-1.5 mm, width 0.68-0.86 mm. Number of spiral cords on last whorls 8-9 (4 above aperture) (See Table 8 and Appendix 19).

REMARKS Simulamerelina novemstriata Faber & Moolenbeek, 2004 from the Cayman Islands ( Faber & Moolenbeek 2004: 61, 62, fig. 2), differs from S. lepteseiras n. sp. in its more slender shell, with a higher height/width ratio (1.88 vs 1.67-1.77 in S. lepteseiras n. sp.); the two spiral cordlets starting after the protoconch-teleoconch boundary vs three in S. lepteseiras n. sp.; the broader and closer basal spiral cordlets; the more numerous axial ribs (17 vs 12 in S. lepteseiras n. sp.); the proportionally smaller aperture (height/ aperture height ratio 2.77 vs 2.20-2.26 in S. lepteseiras n. sp.). See under S. micrometrica n. sp. for detailed comparison.

Figures

FIG. 41. — Simulamerelina lepteseiras n. sp., holotype, Tuamotu. Moruroa, beached, height 1.47 mm, width 0.88 mm, MNHN-IM-2000-38727: A-C, F, shell; E, G, detail of the protoconch; H, detail of the microsculpture of the teleoconch. Scale bars: E, H, 40 μm, D, G, 100 μm.

FIG. 52. — Distribution maps of the Polynesian species of Simulamerelina Ponder, 1985 and Subestea Cotton, 1944: A, Simulamerelina australes n. sp.; B, Simulamerelina densestriata n. sp. (○), Simulamerelina gracilis n. sp. (●), Simulamerelina lepteseiras n. sp. (✩); C, Simulamerelina micrometrica n. sp. (○), Simulamerelina tuamotu n. sp. (●); D, Subestea moruroa n. sp. (○).

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.