Cornisepta marshalli sp. nov.

urn:lsid:zoobank.org:act: 1D805ECB-2850-4290-9696-E9A5E8867488

Fig. 8

Diagnosis

Shell asymmetrically conical, anterior slope longer, straight or lightly convex; posterior slope distinctly concave; protoconch missing; apical foramen at summit of anterior slope, internal transverse septum well developed; shell lacking raised pustules; sculpture primarily of thin, irregularly-spaced, co-marginal ridges; microsculpture extremely fine, comprising concentric ripples and radial threads; translucent white.

Etymology

Named for Dr Bruce Marshall (National Museum of New Zealand – Te Papa Tongarewa), in recognition of his invaluable contribution to vetigastropod taxonomy and systematics, and of his friendship and support during my early career.

Material examined

Holotype

WALTERS SHOAL • empty shell; slopes, stn DW4898; 33°09′ S, 44°01′ E; depth 652–668 m; 6 May 2017; MNHN-IM-2000-38269.

Paratypes

WALTERS SHOAL – slopes • 3 empty shells; stn DW4886; 33°17′ S, 43°56′ E; depth 573–582 m; 3 May 2017; MNHN-IM-2000-38270 • 1 empty shell; stn DW4892; 33°12′ S, 44°01′ E; depth 624– 646 m; 4 May 2017; MNHN-IM-2000-38271 • 1 empty shell; same collection data as for holotype; MNHN-IM-2000-38272 • 1 empty shell; stn DW4900; 33°10′ S, 44°01′ E; depth 660–670 m; 6 May 2017; MNHN-IM-2000-38273.

Description

SHELL. Basal outline evenly elliptical (L/W=1.33–1.36), flat in side view; height moderate (H/L=0.56– 0,72); lateral profile asymmetrically conical; anterior slope longer, straight or slightly convex; posterior slope shorter, distinctly concave; apical foramen at summit of anterior slope, its posterior border higher than anterior one and lateral profile of apex thus somewhat notched (Fig. 8A); internal transverse septum well developed, straight, extending ventrally for about half shell height, its ventral margin shallowly concave; sculpture primarily of thin, irregularly-spaced, co-marginal ridges of uneven strength and sometimes discontinuous; shell lacking raised pustules, but with a rather uneven microsculpture of extremely fine, close-set, concentric ripples crossed by similarly fine radial threads.

PROTOCONCH. Missing.

COLOUR. Translucent white, co-marginal ridges more opaque.

DIMENSIONS. Holotype, base 4.50 × 3.30 mm, height 3.25 mm; largest specimen, base 6.0 × 4.5 mm, height 3.35 mm.

Distribution

Known only from sandy substrata on the slopes of Walters Shoal, at depths of 582–660 m; living specimens unknown.

Remarks

The loss of the protoconch, elevated-conical profile of the shell and strong internal septum clearly ally this species with Cornisepta McLean & Geiger, 1998. However, it differs from other members of this genus in having a sculpture of concentric ridges rather than raised pustules. In terms of its concentric sculpture, C. marshalli sp. nov. somewhat resembles Profundisepta denudata Simone & Cunha, 2014 from Brazil, but that species retains its protoconch and has radial rows of fine pustules.