Shinkailepas conspira Beck, 2023

Chen, Chong & Sigwart, Julia D., 2023, The lost vent gastropod species of Lothar A. Beck, Zootaxa 5270 (3), pp. 401-436 : 419-422

Shinkailepas conspira Beck , sp. nov.

Figs 12 , 13

[ZooBank LSID: urn:lsid:zoobank.org:act:D928F6D9-3542-496A-9162-A5A239720FA3 ]

Type material. Holotype [MNHN-IM-2000-38688] and one paratype in MNHN [Paratype 1: MNHN-IM-2000- 38689], two paratypes in NSMT [Paratype 2: NSMT-Mo 79422; Paratype 3: NSMT-Mo 79423], two paratypes in SMF [Paratype 4: SMF 370381 ; Paratype 5: SMF 370382 ].

Type locality. Lau Basin (Hine Hina) [BIOLAU BL01 ] .

Material examined. The type material and BIOLAU, BL03, 9 specimens [NSMT-Mo 79424]; BIOLAU, BL06, 1 specimen and several shell fragments [ SMF 370383 ], BIOLAU, BL09, 3 specimens and 1 shell fragment [MNHN-IM-2020-12944]; BIOLAU, BL11 [ SMF 370384 ] .

Distribution. Lau Basin at bathyal hydrothermal vents.

Etymology. Species name from Latin roots, con for with, and spira for coiled.

Description. Shell ( Fig. 12 ). Shell large for genus, almost limpet-shaped in adults but with conspicuous remnants of shell-coiling in juveniles; aperture oval in outline; shell margin not in plane, anterior margin clearly overhanging causing an arched line of the margin in a lateral view; apex (oldest shell stages) at posterior shell margin, mostly eroded in adults but intact in juveniles up to about 4 mm; diameter of protoconch about 0.8 mm, coiled several times, reflecting the planktotrophic development; shell surface with fine radial and strong concentric riblets, surface (periostracum) usually of whitish colour, some specimens with large irregular black encrustations (mainly at apex), old shells from Lau Basin completely black; shell interior opaque-white, inner margin of aperture slightly denticulated in juvenile and subadult specimens, otherwise smooth; no overhanging periostracum; at posterior part of shell-interior a strongly marked and thickened septum is evident; left and right muscle scars marked by oval, reniform smooth patches at otherwise rough interior of shell, roughness caused by numerous shell-pores which are concentrated particularly at the interior of the apex.

Dimensions. Holotype: length 21.3 mm, width 19.0 mm, height 9.0 mm.

Radula ( Fig. 13 A-C). Rhipidoglossate, dentition typical for genus, formula 70–80 x 4 x 1 x 4 x 70–80, rachidian teeth rectangular in outline, anterior part equipped with a horseshoe-shaped inner ridge and a much weaker outer ridge; first lateral teeth enlarged and oblique, basal part with U-shaped cross-section, distal part ear-shaped, at transition from basal to distal part, the inner margin forms an overhanging flap. Second lateral small, hook-shaped, overhanging cusp doubled, with 5–7 irregular small denticles. Longish third lateral tooth with deformed cusp, into which the cusp of the second lateral tooth fits in. Fifth lateral tooth with divided base and broadened cusp, showing a broad inner terminal denticle and four more slender outer denticles. At the descending rows of marginal teeth, four types of cusps are recognizable: the innermost type (8 teeth) with long, slender shafts and heavily denticulated cusps, the second type (40–45 teeth) has a terminal slit and denticles of very different size, the third type (approx. 20 teeth) has a fine denticulation and a distal, tongue-like process, the outermost type is simply flabelliform.

Soft parts ( Figs. 13D ). Eyes lacking; cephalic tentacles moderately lang, ventrally equipped with 4–5 stripes of micropapillae; mouth-opening comparatively small, circular, and papillated; oral lobe huge, reaching to the foot sides; cephalic lappets usually small (in females), in males right cephalic lappet modified to function as a penis; foot sole large, only central third ciliated; opening of the anterior foot gland small, slit-like; epipodial lobe extremely enlarged, particularly at the posterior end of foot, bearing up to 60 large, paddle-like flaps arranged in several lines. Pallial margin slightly swollen, pallium thin but not translucent, bearing numerous papillae which are concentrated at the apex; furthermore, minute reddish dots speckle the pallium as well as the neck and gill. In adults, males’ neck extremely swollen forming a transverse ridge which contains spermatophores; pallial cavity deep at left side and shallow at right side; at right neck side, a small field of folds represents the osphradium; gill of moderate size, bipectinated. Operculum [( Fig. 14 )] present at dorsal side of the foot, even in juveniles completely covered by the visceral mass; operculum with an anterior calcareous part, a posterior corneous part and a small paucispiral, corneous nucleus having a small inner process; overall asymmetric, anterior left comer and posterior right corner are lengthened.

Remarks. Shinkailepas conspira sp. nov., is well separated from S. kaikatensis Okutani, Saito & Hashimoto, 1989 from Kaikata Seamount, Japan ( Okutani et al. 1989) and S. tufari Beck, 1992 from Manus Back-Arc Basin, Papua New Guinea ( Beck 1992b) by having the following characters: shell dimensions much larger, shell sculpture with conspicuous concentric riblets; operculum clearly asymmetric; oral and epipodial lobes strongly enlarged, epipodial lobe equipped with several rows of large paddle-like flaps (up to 60).

Figures

FIGURE 12. Shinkailepas conspira sp. nov. A–B. Holotype (shell length 21.3 mm). A. Dorsal view. B. Ventral view. C–E. Paratype 2 (shell length 16.8 mm). C. Dorsal view. D. Ventral view. E. Lateral view. F. Juvenile specimen from BIOLAU, BL06 (shell length 4.0 mm) with coiled protoconch.

FIGURE 13. Shinkailepas conspira sp. nov. A–C. Radula.A. Detail, right half-row. B. Rachidian tooth with anterior, horseshoeshaped ridges. C. Detail of marginal teeth, small arrow points to the tooth-type with distal tongue-like process, large arrow points to the tooth-type defining Shinkailepas. D. Soft parts. Male, anterior part, viewed from ventrally. [Scale bars: A, 50 μm; B, 20 μm; C, 50 μm; D, 1 mm.]

FIGURE 14. Operculum of Shinkailepas conspira sp. nov., (shell length 10.1 mm) in dorsal view.