Simulamerelina densestriata 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 densestriata

description: Simulamerelina densestriata n. sp.
(Figs 38; 39; 52B; 53P; Tables 7; 8; 9)
urn:lsid:zoobank.org:act: 644D549E-259D-4899-8620-C088996F2936
TYPE MATERIAL. — Holotype. Australes • dd (height 2.45 mm, width 1.15 mm, Figs 38 A-C, 39, 53P); Marotiri, BENTHAUS Stn DW1885; 27°52’1”S, 143°33’0”W; 700-800 m; MNHN- IM-2000-38724.
Paratypes. Australes • 41 dd (Fig. 38 D-G); same locality data as holotype; MNHN-IM-2000-38725.
TYPE LOCALITY. — Australes, Marotiri, BENTHAUS Stn DW1885; 27°52’1”S, 143°33’0”W; 700- 800 m.
OTHER MATERIAL EXAMINED. — Australes • 12 dd; Marotiri, BENTHAUS Stn DW1886; 27°51’0”S, 143°31’58”W; 620-1000 m; 6.XI.2002; MNHN • 10 dd; Marotiri, BENTHAUS Stn DW 1884; 27°53’59”S, 143°33’0”W; 570-620 m; 6.XI.2002; MNHN • 1 dd; Tubuai, BENTHAUS Stn DW1962; 23°21’0”S, 149°33’0”W; 470- 800 m; 19.XI.2002; MNHN.
DISTRIBUTION AND SYMPATRY. — Simulamerelina densestriata n. sp. is known from the South Pacific Ocean, in the Australes (Marotiri, Tubuai), with empty shells collected in 570-1000 m (Fig. 52B).
S. densestriata n. sp. is sympatric with S. australes n. sp. in the Australes (Marotiri) (Table 9).
ETYMOLOGY. — The name refers to the dense spiral microsculpture on the teleoconch, from the Latin dense (meaning densely) and striatus, -a, -um (meaning striated).
DIAGNOSIS. — Simulamerelina with large shell for the genus (> 2 mm), slender, pupoid and strong. Paucispiral protoconch. Teleoconch with axial and spiral sculpture of the same strength. Axial ribs fading towards the base. Marked spiral microsculpture. Start of 2 spiral cordlets after protoconch-teleoconch boundary. Colouration uniform white to yellowish.
DESCRIPTION OF HOLOTYPE
Shell (Figs 38 A-C; 39A; 53P)
Large for the genus, height 2.45 mm, width 1.15 mm height/ width ratio 2.17, turriculate-slender, elongate ovate.
Protoconch (Fig. 39B)
Paucispiral with twisted nucleus, of 1.25 convex whorls, height 0.316 mm, nucleus diameter 0.116 mm, first half whorl diameter 0.233 mm, maximum diameter 0.350 mm. Sculpture of 5 spiral cordlets, first, second and fourth more developed; scattered minute granules on last third of whorl. Protoconch-teleoconch boundary well marked.
Teleoconch
Of 4.2 convex whorls, suture large and impressed. Axial sculpture on the last whorl of 14 slightly orthocline ribs, narrower than interspaces, fading toward the base. Spiral sculpture of same strength as axial, of non-equidistant cordlets, 2 on the first whorl, 3 on the second, 8 on the last whorl, of which 3 above the aperture and 5 on the base. Subsutural cordlet more spaced from the others, the basal ones closer each other. Cordlets II and III starting immediately after protoconch-teleoconch boundary; subsutural cordlet I formed on next whorl, weaker; cordlet II most prominent, located on the center of the whorl.Weak, slightly acute tubercles at intersections, interspaces quadrangular. Microsculpture (Fig. 39C) of granulose threads and sparse microgranules. Umbilical fissure very narrow. Aperture oval height 0.82 mm, height/aperture height ratio 2.97, peristome duplicated, internally smooth, externally thickened by a strong opisthocline varix.
Colour
Colouration uniform white to yellowish.
Operculum and soft parts
Unknown.
VARIABILITY
Shell with weak variability.An additional ninth spiral cordlets, entering the narrow umbilical fissure, is infrequently observed. Minimum and maximum height in the examined material, 2.1 and 2.8 mm, respectively. Number of axial ribs on the last whorl varying from 13 to 20. Some specimens orange-pink (see Table 8 and Appendix 17).
REMARKS
Manzonia (Simulamerelina) tokunagai (sensu Hasegawa 2000: 149, pl. 74, fig. 7 non Yokoyama 1927), is very similar to Simulamerelina densestriata n. sp., but it differs in the chromatic pattern, light yellow background, often with indistinct brown spiral bands vs uniform white to orange-pink in S. densestriata n. sp.; the equally spaced spiral cordlets above the aperture vs the subsutural cordlet more spaced from the other two in S. densestriata n. sp.; the number of basal spiral cordlets (4 vs 5-6 in S. densestriata n. sp.).
Simulamerelina australes n. sp. differs from S. densestriata n. sp. in the weaker microsculpture on the teleoconch; the nodulose tubercles at the intersections (vs weaker and slightly acute in S. densestriata n. sp.); the axial ribs reaching the base; the apical sculpture of a keel on the upper fifth, and micro granules on the whole surface vaguely arranged in spiral bands vs five spiral cordlets, the first, second and fourth more developed in S. densestriata n. sp.
See under Simulamerelina gracilis n. sp. for detailed comparisons.
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 860-861, DOI: 10.5252/zoosystema2023v45a25, http://zenodo.org/record/10458066