Manganesepta atiaia new species

Figures 103–108

Types. Holotype MNHN 25317. Paratypes: MNHN 25318, 1 shell, MZSP 102941, 2 shells, all from type locality. Brazil. Espírito Santo; continental slope of Abrolhos (MD55; Bouchet, Leal & Métivier col, 27/v/1987); off Itaúnas, 19°01’S 37°47’W, 1500–1575 m, MNHN 25319, 1 shell, MZSP 102946, 1 shell (sta. CB79).

Type locality. Brazil. Espírito Santo; continental slope of Abrolhos, off Itaúnas, 19°00’S 37°49’W, 950–1050 m (MD55 sta. DC77; Bouchet, Leal & Métivier col, 27/v/1987).

Diagnosis. Height 64% of length. Sculpted by pustules aligned radially, ca. 60 radial alignments, with primary long alignments intercalated with secondary alignments. Protoconch smooth, glossy.

Description. Shell size ca. 5 mm; broadly conical, very-slightly arched posteriorly (Fig. 104); height 64% of length. White, translucent; periostracum beige, dehiscent. Protoconch of 1.5 rounded whorls (Fig. 108); situated on right (Figs 104, 105, 108), forming posterior apex of foramen; smooth, glossy; size 260 µm. Foramen subterminal, approximately diamond-shaped, width ca. 55% of length; dorsally positioned, slightly turned anteriorly; ca. 10% of aperture area; edges irregular (Figs 105, 106). Shell profile almost straight; angle 62°. Sculpture of small pustules aligned in ca. 60 radial alignments (Figs 103–105), primary alignments long clearly intercalated with secondary alignments (with half shell height); pustules elliptical (longer axis parallel to shell edge), separated from neighbor pustules by distance equivalent to half pustule width; interspaces between cords twice as wide as cords. Aperture planar (Fig. 104), elliptical, width 78% of length; edges more or less regular, slightly denticulated by radial alignments. Inner surface smooth, glossy (Figs 106, 107). Septum ca. 40% of shell height; about as tall as wide, ventral edge slightly concave, 37% of aperture width; gradually narrowing up to posterior edge of foramen, constituting posterior and ventral floor of foramen (Fig. 105).

Measurements (in mm). Holotype: 3.5 by 2.0; paratype MZSP 102946: 5.4 by 3.0.

Distribution. Continental slope off Espírito Santo, Brazil.

Habitat. Sandy mud bottoms, 950–1575 m (dead specimens).

Material examined. Types.

Etymology. The specific epithet is derived from the Tupy native language atiaîa, meaning ray, beam of light, an allusion to the outer surface of shell with delicate radial sculpture.

Remarks. The generic attribution of Manganesepta atiaia is based on the large fissure, persistence of protoconch, delicate sculpture, and presence of a septum (McLean & Geiger 1998). Manganesepta atiaia differs from the equatorial Pacific M. hessleri by the more delicate and less dense radial sculpture, in lacking concentric sculpture, and by the wider foramen (Fig. 108). There is not other species in the Atlantic that can be confused with it.