Simulamerelina micrometrica 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
Simulamerelina
Simulamerelina micrometrica

description: Simulamerelina micrometrica n. sp.
(Figs 42; 43; 52C; 53S; Tables 7; 8; 9)
urn:lsid:zoobank.org:act: BFD5B726-DC44-46A7-98A1-C00A1AAE7E36
Simulamerelina sp. 2 – Boutet et al. 2020: 240.
TYPE MATERIAL. — Holotype. Australes • dd (height 1.33 mm, width 0.73 mm, Figs 42 A-C; 43A-C; 53S); E of Rapa, BENTHAUS Stn DW1889; 27°37’1”S, 144°16’1”W; 600-620 m; 7.XI.2002; MNHN-IM-2000-38728.
Paratype. Australes • 1 dd (height 1.46 mm, Figs 42 F-H; 43DF); same locality and data as holotype; MNHN-IM-2000-38729.
TYPE LOCALITY. — Australes: E of Rapa, BENTHAUS Stn DW1889; 27°37’1”S, 144°16’1”W; 600- 620 m.
OTHER MATERIAL EXAMINED. — Australes • 5 dd; Banc Président Thiers, BENTHAUS Stn DW1926; 24°38’9”S, 146°0’50”W; 50-90 m; 13.XI.2002; MNHN • 3 dd; Banc Président Thiers, BENTHAUS Stn DW1932; 24°40’58”S, 146°1’58”W; 500-800 m; 14.XI.2002; MNHN • 3 dd; Banc Président Thiers, BENTHAUS Stn DW1933; 24°40’58”S, 146°1’1”W; 500-850 m; 14.XI.2002; MNHN • 3 dd; N of Raivavae, BENTHAUS Stn DW1943; 23°49’1”S, 147°39’0”W; 950 m; 5.XI.2002; MNHN • 11 dd; Tubuai; 23°20’38”S, 149°28’33”W; beached; sea line; coll. JL • 2 dd; Tubuai, BENTHAUS Stn DW1962; 23°21’0”S, 149°33’0”W; 470-800 m; 19.XI.2002; MNHN • 1 dd; Tubuai, BENTHAUS Stn DW1962; 23°21’0”S, 149°33’0”W; 470-800 m; 19.XI.2002; MNHN • 1 dd; Tubuai, Motu Motihia; 23°22’4”S, 149°23’52”W; beached; beached sediment; coll. JL • 1 dd; Banc Arago, BENTHAUS Stn DW1978; 23°22’1”S, 150°43’1”W; 120-180 m; 21.XI.2002; MNHN • 19 dd; S of Rurutu BENTHAUS Stn DW2010; 22°31’58”S, 151°20’59”W; 520-950 m; 24.XI.2002; MNHN • 13 dd; S of Rurutu BENTHAUS Stn DW2010; 22°31’58”S, 151°20’59”W; 520-950 m; 24.XI.2002; MNHN • 1 dd; E coast of Rurutu, BENTHAUS Stn DW 2003; 22°28’1”S, 151°19’1”W; 250-330 m; 24.XI.2002; MNHN • 1 dd; Rurutu, Toataratara; 22°31’29”S, 151°20’38”W; beached; beached sediment; coll. MB • 15 dd; Rimatara, BENTHAUS Stn DW2020; 22°37’1”S, 152°49’1”W; 920-930 m; 25.XI.2002; MNHN • 2 dd; Rimatara, BENTHAUS Stn DW2021; 22°37’1”S, 152°49’1”W; 1200-1226 m; 25.XI.2002; MNHN • 4 dd; Rimatara, BENTHAUS Stn DW2021; 22°37’1”S, 152°49’1”W; 1200-1226 m; 25.XI.2002; MNHN. Gambier • 1 dd; Mangareva, Rikitea; 23°6’39”S, 134°58’1”W; beached; lagoon; coll. JL • 4 dd; Mangareva, Rikitea; 23°6’39”S, 134°58’1”W beached; beached sediment; coll. MB.
Tuamotu • 1 dd; Gatavake; 23°6’50”S, 134°58’55”W- 23°6’50”S, 134°58’55”W; 1-3 m; coll. JL • 1 dd; Tenoko; 23°4’26”S, 135°0’35”W; 1-3 m; coll. JL • 2 dd; Totegegi; 23°5’2”S, 134°52’58”W; 1-3 m; coll. JL • 1 dd; Moruroa; 21°46’37”S, 138°53’31”W; beached; on the sea-line; coll. MB • 1 dd; Vairaatea; 19°19’44”S, 139°13’8”W; beached; coll. MB.
Society Islands • 36 dd; Motu One; 15°48’21”S, 154°30’39”W; 1 m; reef edge; coll. JL.
DISTRIBUTION AND SYMPATRY. — Simulamerelina micrometrica n. sp. is known from the South Pacific Ocean, in the Australes (Rapa, Banc Président Thiers, Raivavae, Tubuai, Banc Arago, Rurutu, Rimatara), Gambier, Tuamotu (Moruroa) and Society Islands (Motu One) (Fig. 52C).
Simulamerelina micrometrica n. sp. is sympatric with S. australes n. sp. in the Australes (Rapa, Banc Président Thiers Banc, Arago, Rurutu, Rimatara) and with Simulamerelina densestriata n. sp. in the Australes (Tubuai) (Table 9).
ETYMOLOGY. — The name refers to the small size of this species, from the Greek μΙκΡός (meaning small) and μΕΤΡΙκός (meaning metric).
DIAGNOSIS. — Simulamerelina with small shell for the genus (<2 mm), slender, turriculate and robust. Protoconch paucispiral. Teleoconch axial and spiral sculpture of same strength, axials fading at the base. Cordlet II most prominent. Microsculpture of dense spiral threads. Start of 2 spiral cordlets after protoconch-teleoconch boundary. Colouration uniform white.
DESCRIPTION OF HOLOTYPE
Shell (Figs 42 A-C; 43A; 53S)
Small for the genus, height 1.33 mm, width 0.73 mm height/ width ratio 1.82, turriculate-slender, elongate ovate, robust.
Protoconch (Fig. 43B)
Paucispiral with weakly twisted nucleus, of 1.35 convex whorls, height 0.277 mm, nucleus diameter 0.083 mm, first half whorl diameter 0.167 mm, maximum diameter 0.283 mm. Sculpture of one spiral keel on upper third, microgranules over the entire surface. Protoconch-teleoconch boundary well marked.
Teleoconch
Of 2.9 convex whorls, suture evident and impressed. Axial sculpture on last whorl of 18 orthocline ribs, slightly prosocline, thinner than interspaces and not reaching the base. Spiral sculpture of same strength as axial, of equidistant cordlets, 2 central on first whorl, 3 on the next, 8 on last whorl, of which 3 above the aperture, the subsutural very weak, and 5 on the base. Cordlet II most prominent. Slightly acute tubercles at the intersections, interspaces quadrangular. Microsculpture (Fig. 43C) of dense spiral threads. Umbilical fissure absent. Aperture oval, height 0.50 mm, height/aperture height ratio 2.66, peristome duplicated, internally smooth, externally thickened by a strong slightly prosocline varix.
Colour
Colouration uniform white.
Operculum and soft parts
Unknown.
VARIABILITY
Minimum and maximum dimensions: height 1.13-1.67 mm, width 0.68-0.86 mm. Number of axial ribs on the last whorl: 13-24. Outer lip varix breadth corresponding to 3-6 appressed ribs (See Table 8 and Appendix 20).
REMARKS
Simulamerelina wanawana (Kay, 1979) from Barbers Point, Oahu, Hawaii (Kay 1979: 82, fig. 28a, b), is similar to S. micrometrica n. sp., but differs in the sculpture of the protoconch of 1.5 whorls, with abapical spiral striae vs 1.25-1.4 whorls with one adapical spiral keel on the upper third, and microgranules over the entire surface in S. micrometrica n. sp.; the larger size (height 1.75-1.80 mm vs height 1.23-1.67 mm in S. micrometrica n. sp.). Hasegawa (2000: 150, 151, fig. 18a-c) has figured two ‘forms’ of Merelina wanawana Kay, 1979 from Japan: its spiny form (Hasegawa 2000: fig. 18c) morphologically fits the real S. wanawana of Hawaii; the specimen with more numerous axial ribs (Hasegawa 2000: fig. 18a, b) is very similar to our Polynesian specimens of S. micrometrica n. sp., apparently larger (1.8 mm) and with a narrower protoconch.
Simulamerelina longinqua (Rehder, 1980) from Easter Island (Rehder 1980: 29, pl. 5, fig. 10), differs from S. micrometrica n. sp. in the larger size (height 1.8-2.01 mm vs height 1.23- 1.67 mm), and the different apical sculpture (two or three spiral cordlets, the abapical very weak, the apical forming a keel producing a flattened ramp vs one spiral keel on upper third, microgranules over the entire surface in S. micrometrica n. sp.).
Simulamerelina caribaea (d’Orbigny, 1842) from Cuba and Jamaica (d’Orbigny 1842: 21, pl. 11, figs 31-33), superficially resembles S. micrometrica n. sp. but can be separated by the chromatic pattern, white background with two reddish-brown subsutural and basal bands vs uniform white in S. micrometrica n. sp.; the larger size (height 1.8-2.0 mm vs height 1.23- 1.67 mm in S. micrometrica n. sp.); the spiral sculpture of three spiral cordlets above the aperture, of the same thickness, vs one (subsutural) very weak and two stronger cordlets In S. micrometrica n. sp.
Simulamerelina lepteseiras n. sp. superficially resembles S. micrometrica n. sp. but can be separated by its more numerous spiral cordlets (four on the upper whorls, and nine on the last whorl, four above the aperture, vs three on the upper whorls and eight on the last whorl, three above the aperture in S. micrometrica n. sp.), and its broader aperture
Simulamerelina tuamotu n. sp. has a protoconch with similar sculpture but with less convex whorls; fewer axial ribs (8-13 vs 13-24 in S. micrometrica n. sp.); 4-5 spiral cordlets on the base vs four in S. micrometrica n. sp.; the median spiral cordlet decidedly the more protruding and broader vs the spiral cordlets above the aperture almost of the same thickness in S. micrometrica n. sp.
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 864-868, DOI: 10.5252/zoosystema2023v45a25, http://zenodo.org/record/10458066