Serrata inflata, 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 : 415-418

Serrata inflata n. sp.

Fig. 39

TYPE MATERIAL. — Holotype (dd) MNHN 20619 .

TYPE LOCALITY. — Northeastern New Caledonia, Passe de Hienghu , 20°33’S, 165°00’E, 270-282 m [BATHUS 1: stn DW 688] .

MATERIAL EXAMINED. — Northeastern New Caledonia. BATHUS 1: stn DW 688, 20°33’S, 165°00’E, 270-282 m, 1 dd (holotype, Fig. 39) .

DISTRIBUTION. — Northeastern New Caledonia, one shell in 270-282 m.

DESCRIPTION. — Shell bulbous, rounded, weakly pyriform, solid, subtranslucent. Protoconch paucispiral, wide, very narrow, smooth. Spire very short, blunt. Aperture narrow, sinuous, oblique, anterior part widening slightly. Base bluntly tapering. Outer lip strongly thickened, slightly reflected over lower half, shoulder high, rounded, outer edge very arched, outer margin very thick, rounded, stepped, inner edge slightly sinuous, lower part excavated, bearing 3 well-defined low denticles, 6 ill-defined tiny denticles on central part, other denticles suggested but indistinct along upper part. Four thin, oblique columellar plaits, 3 anterior closely packed ones visible outside aperture, fourth one well-defined but hidden on internal part of columella.

Ground colour pale yellowish-amber, outer margin white, suprasutural zone intense white.

Dimensions: 2.25 x 1.55 mm.

Radula unknown.

REMARKS. — The generic placement of Serrata inflata is based mainly on the outer lip morphology, with an excavated anterior part bearing 3 distinct well-spaced denticles, followed by a series of smaller denticles on the central part of the inner edge. This kind of outer lip morphology is very common in Serrata and has no equivalent in other marginellid genera. Serrata inflata differs from Cystiscus species (family Cystiscidae Stimpson, 1865 ) in its well-defined, stepped outer margin. Despite its general outline, it cannot be placed in Granulina because of the well-defined short spire of S. inflata (rather than the sunken one of Granulina ), its smooth surface lacking microsculpture, and the simple pattern of columellar plaits, which are biplicate or angular inside the aperture in Granulina (cf. Boyer & Rolán 2004).

On the other hand, the shell morphology of S. inflata is not so different from that of S. translata (Fig. 4), which has a similar, inflated, somewhat heart-shaped outline, with a very low, blunt spire, a similar organisation and shape of the 3 lower columellar plaits (the fourth tiny plait being visible externally but well-separated in S. translata ), a similar, long, narrow aperture, and a similar outer lip slightly excavated over the anterior part and showing the same organisation and shape of the labial denticles. Serrata inflata also has morphological affinities with S. granum (Fig. 38), and in my opinion both species belong in the S. translata species group. The uniform yellowish-amber ground colour of S. inflata (also found for instance in S. tahanea Wakefield & McCleery, 2002 from the Tuamotu Islands) is within the range of variation in Serrata species and in the S. translata species group itself (see Wakefield & McCleery 2002).

FIGS 33-48. 33, Serrata perlucida n. sp., holotype MNHN 20613, Norfolk Ridge, BIOCAL stn CP 61, H 6.90 mm. 34, Serrata laevis n. sp., holotype MNHN 20615, Norfolk Ridge, BERYX 11 stn DW 09, H 5.10 mm. 35, Serrata carinata n. sp., holotype MNHN 20616, Norfolk Ridge, BERYX 11 stn DW 09, H 6.65 mm. 36, Serrata tenuis n. sp., holotype MNHN 20617, southern New Caledonia, BIOCAL stn DW 48, H 5.40 mm. 37, Serrata beatrix ( Cossignani, 2001) , holotype MNHN 0370, northern New Caledonia, TUI 2, H 6.63 mm. 38, Serrata granum n. sp., holotype MNHN 20618, Norfolk Ridge, BATHUS 3 stn DW 827, H 4.00 mm. 39, Serrata inflata n. sp., holotype MNHN 20619, northeastern New Caledonia, BATHUS 1 stn DW 688, H 2.25 mm. 40, Serrata stylaster ( Boyer, 2001) , holotype MNHN 20748, Norfolk Ridge SMIB 8 stn DW 167, H 4.70 mm. 41-43, Serrata tuii ( Cossignani, 2001) ; 41, holotype MNHN 1430, northern New Caledonia, TUI 2, H 9.70 mm; 42, northern New Caledonia, BATHUS 4 stn DW 927, H 8.35 mm; 43, northern New Caledonia, MUSORSTOM 4 stn DW 197, H 10.80 mm. 44, Serrata robusta n. sp., holotype MNHN 20620, southern New Caledonia, SMIB 8 stn DW 201, H 6.90 mm. 45-47, Serrata magna n. sp.; 45, holotype MNHN 20622, southern New Caledonia, BIOCAL stn DW 51, H 9.70 mm; 46, BIOCAL stn DW 48, H 10.00 mm; 47, BIOCAL stn DW 48, H 10.10 mm. 48, Serrata robusta n. sp., southern New Caledonia, BATHUS 2 stn DW 720, H 7.10 mm.

Serrata inflata differs from S. translata and from S. granum in its more rounded and stouter outline, its wider aperture, its more reflected and sinuous outer lip, and its 3 visible columellar plaits. Serrata inflata differs also from S. translata in its smaller protoconch, and from S. granum in its wider protoconch and its slightly larger spire.

ETYMOLOGY. — Latin inflatus (adj., swollen, inflated), referring to the bulbous outline of the shell.