Serrata dentata, Boyer, 2008

Boyer, Franck, 2008, The genus Serrata Jousseaume, 1875 (Caenogastropoda: Marginellidae) in New Caledonia, Mémoires du Muséum national d'Histoire naturelle 196, pp. 389-436 : 403-404

Serrata dentata n. sp.

Figs 19, 20

TYPE MATERIAL. — Holotype (lv) MNHN 20599 and 4 paratypes (lv and dd) MNHN 20600 .

TYPE LOCALITY. — Southern New Caledonia, 22°48’S, 167°16’E, 444-445 m [BATHUS 2: stn DW 719] .

MATERIAL EXAMINED. — Southern New Caledonia. BIOCAL: stn DW 33, 23°10’S, 167°10’E, 675-680 m, 1 dd; stn DW 44, 22°47’S, 167°14’E, 440-450, 10 dd; stn DW 48 ,

23°00’S, 167°29’E, 775 m, 1 dd. — BATHUS 2: stn DW 719, 22°48’S, 167°16’E, 444-445 m, 3 lv, 2 dd (holotype, Fig. 19 and 4 paratypes, Fig. 20).

DISTRIBUTION. — Southern New Caledonia, live in 444-445 m, shells in 445-775 m.

DESCRIPTION. — Shell slender ovate, fusiform, solid, subtranslucent. Protoconch paucispiral, small, slightly bulging, smooth. Spire moderate-sized, narrow, conical, whorls faintly convex. Aperture narrow, very oblique, gently widening towards base. Base rather tapering. Outer lip nearly vertical, thickened in the centre, narrowed posteriorly and along anterior third, weakly reflected. Shoulder short, moderately sloping, its outline making a double angle, anterior half of edge weakly oblique, outer margin thick, protruding, flat, stepped, inner edge faintly oblique, nearly straight, bearing 12 sharp, subequal, well spaced denticles. Five narrow columellar plaits, 2 anterior ones oblique and nearly straight, second one very long, 3 upper ones less oblique, decreasing in size posteriorly, fifth plait not fully formed.

Ground colour whitish opalescent, with 2 pale narrow orange bands on dorsum, both more marked on outer margin than elsewhere and decreasing in intensity over last whorl.

Dimensions: 6.90 x 3.15 mm

Radula unknown.

REMARKS. — The shell outline of Serrata dentata ranges from slender to moderately ovate (Figs 19-20). The anterior part of the aperture widens weakly in most specimens, but opens slightly more widely in a few specimens (Fig. 20). Other shell morphology characters are very constant, especially the shape, thickness and position of the columellar plaits, and the number, size and position of the labial denticles. The length ranges from 5.50 to 6.90 mm. The species seems to be moderately common within its range (known from 22°47’S to 23°10’S).

Serrata dentata is very similar to S. aureosa , principally in shell length and in the organisation and length of its columellar plaits. However, S. dentata differs from S. aureosa in several constant characters: its more ovate outline, the smaller number of sharper and more widely spaced labial denticles (11-12 in S. dentata , 13-17 in S. aureosa ), the more strongly reflected inner labrum, and the decoration of 2 pale, narrow orange bands on a whitish ground instead of a uniform light amber dorsum and medium golden amber outer margin in S. aureosa (holotype).

Despite obvious similarities between the two species and the narrow distribution of S. aureosa within the geographic range of S. dentata , no intergrades have been seen.

ETYMOLOGY. — Latin dentatus (adj., having teeth), referring to the prominent subequal labial denticles of this species.