Belomitra minutula, Kantor & Puillandre & Rivasseau & Bouchet, 2012

Kantor, Yuri I., Puillandre, Nicolas, Rivasseau, Audrey & Bouchet, Philippe, 2012, 3496, Zootaxa 3496, pp. 1-64 : 52-54

Belomitra minutula new species

Figures 20, 31, 32

Type material: Holotype MNHN 24497 (sequenced as MNHN IM200918857 ) (measurements: SL 8.4 mm, BWL 5.6, AL 4.0, SW 3.3 mm), 4 paratypes MNHN 24498 (1 sequenced as MNHN IM200918858 ).

Type locality: Coral Sea , east Bellona Plateau, 21º06’S, 158º37’E, 488–493 m, 11 October 2005 [EBISCO sta. DW2546 ] .

Material examined: CORAL SEA. EBISCO, sta. DW2546 , 21º06’S, 158º37’E, 488–493 m, 2 lv, 3 dd (holotype and paratypes) .

Description (holotype, Fig. 31A–C): Shell small, solid, glossy, turriform, with elevated spire, consisting of ca. 1.5 protoconch and 4.5 convex teleoconch whorls which are slightly angulated at shoulder. Protoconch globose, smooth, ca 950 µm in diameter, height 700 µm. Protoconch-teleoconch transition marked by weak orthocline rib. Suture deeply impressed. Last whorl high, 0.66 of SL, evenly convex. Subsutural ramp present on all teleoconch whorls, poorly defined, very slightly concave. Beside numerous growth lines, axial sculpture consisting of narrow, closely spaced, and very weakly recurved, orthocline ribs. Number of ribs increasing from 12 on first teleoconch whorl to 16 on penultimate and 23 on last whorl. Ribs extending from suture to suture on spire whorls and to canal on last whorl. Spiral sculpture of distinct, low, narrow, closely spaced cords, poorly visible between ribs, of even width, covering entire shell surface, most of them subdivided by very narrow groove. Subsutural cord larger than others, 2 smaller cords on subsutural ramp, 4–5 below ramp on teleoconch whorls and 21 below ramp on last whorl. On intersections with axial ribs cords form small, oval knobs. Aperture medium high, 0.47 of SL, narrowelongate, poorly delimitated from short and broad siphonal canal, slightly recurved to left. Outer lip thin, very slightly concave adapically and convex and evenly rounded abapically. Columella slightly convex, nearly straight, smooth. Callus narrow, of thin transparent glaze overlying the parietal region. Siphonal notch absent. Shell colour off-white. Periostracum absent.

Operculum ( Fig. 31H) of paratype 2 is of medium size, oval, long axis of nucleus at approximately 60º to main axis of operculum. Nucleus terminal, partially abraded.

Radula of holotype ( Fig. 32) short, consisting of about 65 rows of teeth (7 nascent), 0.78 mm long (0.20 AL), narrow, about 30 µm in width (0.75% of AL). Lateral teeth about 45 µm in maximum length (1.1% of AL), with narrow base and rounded posterior edge. Laterals bicuspid, inner cusp much longer than outer one. Outer cusp situated at outer surface of tooth and not seen in dorsal view ( Fig. 32A, upper row of teeth). Rachidian teeth rather broadly spaced and cusps only slightly overlapping previous row. Tooth base trapezoidal, with slightly notched broader anterior edge and rounded angles. Three weak, narrow cusps (central longest) emanating from posterior edge of tooth base. Anteriormost rows of teeth showing extreme wear ( Fig. 32C), cusps of lateral teeth completely worn off. Radula of paratype ( Fig. 32D) very similar to holotype.

Distribution: Known only from type locality ( Fig. 20).

Etymology: Minutulus (adjective) is a diminutive of minutus, Latin for small.

Remarks: The sequenced paratype 2 (MNHN IM200918858) was cracked prior to fixation, but the remaining shell parts leave no doubts on its identity. Dead collected paratypes 3 and 4 ( Fig. 31D–E, F–G respectively) are rather similar to holotype, varying slightly in having less prominent spiral cords.

The only species which can be compared with Belomitra minutula is B. granulata . The latter can be easily differentiated by its characteristic beaded shell surface and the presence of columellar plaits.