Benthobrookula laticostata, Herbert, 2024

Herbert, David G., 2024, The Vetigastropoda (Mollusca) of Walters Shoal, with descriptions of two new genera and thirty new species, European Journal of Taxonomy 923, pp. 1-119 : 59-60

Benthobrookula laticostata sp. nov.

urn:lsid:zoobank.org:act:032568BA-403D-46F9-AD78-4D1249A81AD5

Figs 24G–I , 25C, H

Diagnosis

Shell turbiniform, H/D ± 1.0, whorls evenly rounded, broadly umbilicate; teleoconch sculptured with axial ribs, 13–16 on first whorl, penultimate and last adult whorls each with 14–18; ribs broad and robust, weakly prosocline, their intervals with fine, close-set, spiral threads which ascend and cross ribs; ribs weakening and appearing to split into 3–4 finer riblets below periphery, evanescing prior to umbilicus; umbilicus sculptured with uneven, undulant spiral cords; protoconch globose and exsert.

Etymology

From the Latin “ latus ” – “broad, wide” and “ costa, costata ” – “a rib, ribbed”; in reference to the sculpture of strong, stout ribs.

Material examined

Holotype

WALTERS SHOAL • empty shell; slopes, stn CP4907; 33°27′ S, 44°00′ E; depth 880 m; 9 May 2017; MNHN-IM-2000-38080 .

Paratypes

WALTERS SHOAL • 2 empty shells; same collection data as for holotype; MNHN-IM-2000-38081 • 3 empty shells; slopes, stn DW4899; 33°09′ S, 44°02′ E; depth 707–720 m; 6 May 2017; MNHN- IM-2000-38082 • 1 empty shell; south plain, stn CP4913; 33°52′ S, 44°05′ E; depth 1539–1615 m; 11 May 2017; MNHN-IM-2000-38083 .

Description

SHELL. Minute (height up to 1.0 mm), turbiniform; height and diameter more or less equal; whorls rounded, suture strongly indented; periphery evenly rounded, close to mid-whorl; base rounded, broadly umbilicate; teleoconch of up to 2.5 whorls. First teleoconch whorl with 13–16 broad axial ribs, increasing in strength toward end of whorl; subsequent whorls with similar ribs, progressively more widely spaced; penultimate and last adult whorls each with 14–18 ribs; ribs weakly prosocline, broad and robust, but often weakening prior to outer lip; intervals between ribs 2–3 times wider than ribs, sculptured by fine, close-set, spiral threads ( Fig. 25H ); threads ascend and cross ribs (though often worn on rib crest); rib intervals also with even finer, more close-set axial threads (visible only under SEM); ribs weakening and appearing to split in to 3–4 finer riblets below periphery, evanescing prior to umbilicus; umbilicus relatively broad with evenly rounded margin, its interior sculptured only with uneven, undulant spiral cords. Aperture circular; peristome complete, almost radial, its edge simple; interior not obviously nacreous.

PROTOCONCH ( Fig. 25C ). Globose and exsert; diameter ±210 μm, ca 1.25 whorls; with sculpture of fine anastomosing threads producing network of close-set, irregularly-shaped pits; terminal lip more or less straight, not thickened.

COLOUR. Uniformly white; freshest specimens somewhat translucent.

DIMENSIONS. Holotype, height 1.0 mm, diameter 1.0 mm (= largest specimen).

Distribution

Known only from the slopes and surrounding plain of Walters Shoal, at depths of 720–1539 m, on sandy substrata; living specimens unknown.

Remarks

Benthobrookula laticostata sp. nov. resembles Be. valdiviae ( Thiele, 1925) , from a depth of 693 m off the Kenya-Somalia border, but the latter is larger, proportionately more elevated (height 2.1 mm, diameter 1.8 mm), has a more cyrtoconoid profile and possesses more numerous, more close-set axial ribs (20 on the last adult whorl). Benthobrookula conica (Watson, 1886) from off Brazil is similar, but has narrower ribs that remain strong on the base and continue into the umbilicus ( Absalão et al. 2001; Absalão & Pimenta 2005). Like Be. laticostata, Be. olearia ( Absalão & Pimenta, 2005) from off southern Brazil has robust axial ribs, but they are more numerous (23 on last adult whorl) and more distinctly prosocline, its spire is less elevated and it has coarser peri-umbilical spiral cords.

Figures

Fig. 24. A–C. Benthobrookula araneum sp. nov. A–B. Holotype, height 1.2 mm (MNHN-IM-2000- 38068). C. Paratype, diameter 1.1 mm (MNHN-IM-2000-38069). D–F. Benthobrookula galeneae sp. nov. D–E. Holotype, height 1.25 mm (MNHN-IM-2000-38075). F. Paratype, diameter 1.2 mm (MNHN-IM-2000-38076). G–I. Benthobrookula laticostata sp. nov. G–H. Holotype, diameter 1.0 mm (MNHN-IM-2000-38080).I.Paratype,diameter1.0mm(MNHN-IM-2000-38082).J–L.Benthobrookula scalaroides sp. nov. J–K. Holotype, height 1.14 mm (MNHN-IM-2000-38084). L. Paratype, diameter 1.0 mm (MNHN-IM-2000-38085). M–O. Benthobrookula semisculpta sp. nov. M–N. Holotype, height 1.4 mm (MNHN-IM-2000-38088). O. Paratype, diameter 1.4 mm (MNHN-IM-2000-38090).

Fig. 25. A, F. Benthobrookula araneum sp. nov. A. Protoconch (paratype, MNHN-IM-2000-38069). F. Sculptural detail at start of last adult whorl, holotype. B, G. Benthobrookula galeneae sp. nov. B. Protoconch (paratype, MNHN-IM-2000-38076). G. Sculptural detail at start of last adult whorl, holotype. C, H. Benthobrookula laticostata sp. nov. C. Protoconch, DW4899 (paratype, MNHN- IM-2000-38082. H. Sculptural detail at start of last adult whorl, holotype. D, I. Benthobrookula scalaroides sp. nov. D. Protoconch (paratype, MNHN-IM-2000-38085). I. Sculptural detail at start of last adult whorl, holotype. E. Benthobrookula semisculpta sp. nov., protoconch CP4911 (paratype, MNHN-IM-2000-38090). Scale bars=100 μm.