Emarginula lentiginosa, 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 : 4-7

Emarginula lentiginosa sp. nov.

urn:lsid:zoobank.org:act:BDBEBCEE-044B-405A-B4FB-78CCB37B4E7D

Fig. 2

Diagnosis

Shell small, apex strongly recurved, extending well beyond posterior margin of base; slit approx. 0.25– 0.33 length of anterior slope; selenizone at most weakly sunken with elevated margins and regular, moderately coarse lunulae; sculpture finely and crisply cancellate, interstices simple; radial ribs with rounded nodules where crossed by concentric ridges; pale buffish-white with small brownish spots on radial ribs; no broad blotches of colour on anterior face.

Etymology

From the Latin “ lenticula ” – “a freckle”; in reference to the colour pattern of small brown spots.

Material examined

Holotype

WALTERS SHOAL • empty shell; slopes, stn DW4881; 33°16′ S, 43°50′ E; depth 377–382 m; 2 May 2017; MNHN-IM-2000-38246 .

Paratypes

WALTERS SHOAL – slopes • 2 empty shells; stn DW4880; 33°17′ S, 43°51′ E; depth 275–318 m; 1 May 2017; MNHN-IM-2000-38247 • 7 empty shells; same collection data as for holotype; MNHN- IM-2000-38248 • 1 empty shell; stn DW4887; 33°17′ S, 43°57′ E; depth 599–640 m; 3 May 2017; MNHN-IM-2000-38249 • 2 empty shells; stn DW4890; 33°09′ S, 43°59′ E; depth 492–588 m; 4 May 2017; MNHN-IM-2000-38250 • 5 empty shells; stn DW4893; 33°16′ S, 43°58′ E; depth 623–629 m; 4 May 2017; MNHN-IM-2000-38251 .

Other material

WALTERS SHOAL – slopes • 3 empty shells; stn DW4877; 33°10′ S, 43°49′ E; depth 217– 256 m; 1 May 2017; MNHN • 6 empty shells; stn DW4879; 33°17′ S, 43°52′ E; depth 288–300 m; 1 May 2017; MNHN • 7 empty shells; stn DW4880; 33°17′ S, 43°51′ E; depth 275–318 m; 1 May 2017; MNHN • 50+ empty shells; same collection data as for holotype; MNHN • 12 empty shells; stn DW4885; 33°17′ S, 43°55′ E; depth 272–380 m; 3 May 2017; MNHN • 20+ empty shells; stn DW4886; 33°17′ S, 43°56′ E; depth 573–582 m; 3 May 2017; MNHN • 13 empty shells; stn DW4887; 33°17′ S, 43°57′ E; depth 599–640 m; 3 May 2017; MNHN • 9 empty shells; stn DW4890; 33°09′ S, 43°59′ E; depth 492–588 m; 4 May 2017; MNHN • 8 empty shells; stn DW4892; 33°12′ S, 44°01′ E; depth 624–646 m; 4 May 2017; MNHN • 10 empty shells: stn DW4893; 33°16′ S, 43°58′ E; depth 623–629 m; 4 May 2017; MNHN • 1 empty shell; stn DW4894; 33°09′ S, 43°50′ E; depth 199–261 m; 5 May 2017; MNHN • 7 empty shells; stn DW4897; 33°09′ S, 43°59′ E; depth 490–584 m; 5 May 2017; MNHN • 6 empty shells; stn DW4898; 33°09′ S, 44.01′ E; depth 652–668 m; 6 May 2017; MNHN • 3 empty shells; stn DW4899; 33°09′ S, 44°02′ E; depth 707–720 m; 6 May 2017; MNHN • 6 empty shells; stn DW4900; 33°10′ S, 44°01′ E; depth 660–670 m; 6 May 2017; MNHN • 2 empty shells; stn CP4902; 33°08′ S, 44°02′ E; depth 700–711 m; 7 May 2017; MNHN .

Description

SHELL. Small (basal length up to 6.0 mm), strongly recurved, apex extending well beyond posterior margin of base; basal outline broadly ovate (L/W ± 1.45), slightly concave in side view; height moderate (H/L 0.51–0.57); anterior slope strongly convex; posterior slope concave. Anterior slit moderately deep, 0.25–0.33 length of anterior slope; selenizone initially forming a low mid-line rib with scarcely raised margins, but margins becoming more elevated with growth, though frequently damaged; lunulae of selenizone moderately coarse and regular; final part of selenizone at most weakly sunken; remaining sculpture cancellate, comprising ± 16 primary radial ribs with further secondary and tertiary ribs between them; radial sculpture crossed by concentric ridges, similar to secondary ribs in strength; ribs with rounded nodules where crossed by concentric ridges; interstices between ribs and ridges almost square, forming a crisp reticulation, each interstice with a pair of radially elongate intritacalx pits; pits often joined apically and diverging basally; basal margin unevenly crenulated by ends of radial ribs; interior with thickened rim surrounding anterior slit, extending apically as a broad, low mid-line ridge, of similar length to the slit itself; interior of recurved apex scarcely visible or not visible in largest specimens.

PROTOCONCH ( Fig. 2G ). Typically emarginuliform; single whorl with a thickened terminal varix; sculpture with flocculated superficial granulation; maximum diameter ± 165 μm.

COLOUR. Fresh specimens pale buffish-white, recurved apex generally whiter; radial ribs with small brown or olive-brown spots ( Fig. 2E–F ); spotted ribs usually, but not always alternating with unspotted ribs. No broad blotches of colour on anterior face. The holotype is not fresh and its colour pattern has faded.

DIMENSIONS. Holotype, base 8.4× 5.8 mm, height 4.3 mm (= largest specimen).

Distribution

Common as empty shells on the slopes of Walters Shoal, at depths of 256–707 m; dredged and trawled on a variety of sandy substrata; living specimens unknown.

Remarks

In terms of its general shape and sculpture, Emarginula lentiginosa sp. nov. is allied to a number of species. The most geographically proximate of these is E. natalensis Barnard, 1963 , a common species off the eastern seaboard of southern Africa ( Herbert 2015). That species, however, is generally less strongly recurved, its selenizone is noticeably sunken and the shell has a greenish colour with darker blotches on the anterior slope ( Herbert & Kilburn 1986). The material recorded as E. natalensis by Barnard (1963a) from Africana stn A1248 on the Sapmer Bank Seamount adjacent to the Southwest Indian Ridge may well in fact be E. lentiginosa [cf. Imbricoscelis coronis (Barnard, 1963) which also occurs at both localities (see below)]. Also similar is E. harmilensis Sturany, 1903 from the Red Sea, the holotype of which was recently illustrated by Albano et al. (2017). This too is less strongly recurved and has a sunken selenizone, and its colour pattern includes bold brown blotches on the anterior face (see also Singer 1998). I cannot agree with the conclusion of Geiger (in Albano et al. 2017) that this species is a synonym of E. costulata Deshayes, 1863 from the south-western Indian Ocean. That species is less strongly recurved, has coarser sculpture with compound interstices and is of an olive-green colour ( Kilburn 1978 (as E. tenuicostata ); Drivas & Jay 1985; Herbert & Kilburn 1986 (as E. tenuicostata ); Herbert 1987a) [illustrations of lectotype available from https://science.mnhn.fr/institution/mnhn/collection/im/item/2000-4750]. Emarginula maculata A. Adams, 1863 from southern Japan and the Philippines ( Sasaki 2000a; Poppe & Tagaro 2020) is another similar species, but this too has a mottled rather than a finely spotted colour pattern and has bold blotches on the anterior face. Emarginula curvata Schepman, 1908 from the Sulu Archipelago has finer radial sculpture, a sunken selenizone and lacks the freckled colour pattern.

Figures

Fig. 2. Emarginula lentiginosa sp. nov. A–D. Holotype, base 8.4×5.8 mm, height 4.3 mm (MNHN- IM-2000-38246). E–F. Fresh specimen retaining colour pattern, stn DW4893, basal length 5.9 mm (paratype, MNHN-IM-2000-38251). G. Protoconch, stn DW4893, scale bar =100 μm (paratype, MNHN-IM-2000-38251).