Ethminolia hickmanae, Herbert, 2024

Herbert, David G., 2024, The Umboniinae (Mollusca: Gastropoda: Trochidae) of New Caledonia, with descriptions of two new genera and eight new species, plus an additional new species from the Bismarck Sea, European Journal of Taxonomy 973, pp. 1-143 : 100-105

Ethminolia hickmanae sp. nov.

urn:lsid:zoobank.org:act:3F15988B-094D-44F8-ADA4-93FFBE1C7399

Figs 53–56

Diagnosis

Shell very small with low spire and rounded whorls; base widely umbilicate; sculpture of 6–8 low spiral cords, widely-spaced axial riblets and microscopic axial threads; umbilicus lacking funicle, its rim evenly rounded; aperture circular, peristome subradial, almost complete, outer lip simple. Colouration highly variable; usually mottled with dark and light spots, blotches and flames; spiral cords commonly spotted, dark on light and light on dark.

Etymology

Named for Prof. Carole Hickman, University of California Museum of Paleontology, in recognition of her excellent research on trochoidean vetigastropods.

Material examined

Holotype ( Fig. 53A–C )

NEW CALEDONIA – Grande Terre • living specimen; Koumac, Stn KD 561; 20°45.4′ S, 164°14.4′ E; depth 1 m; 14 Nov. 2019; KOUMAC 2.3 leg.; sable grossier; MNHN-IM-2000-38863 .

Paratypes

NEW CALEDONIA – Grande Terre • 5 specimens, living; same data as for holotype; MNHN- IM-2000-38864 • 4 specimens, living; Koumac, Stn KD530; 20°32.1′ S, 164°11′ E; depth 10 m; 4

Nov. 2019; Koumac 2.3 leg.; sable, algues brunes, Halimeda ; DNA vouchers: MNHN-IM-2019-3872, -3873, -3874 and -3875 (image LC282 ) • 1 specimen, living; same collection data as for preceding; MNHN-IM-2000-29842 • 1 specimen, living; Koumac , Stn KD 547; 20°42.2′ S, 164°18.2′ E; depth 2–6 m; 8 Nov. 2019; KOUMAC 2.3 leg.; sable grossier et herbier; DNA voucher, photographed alive (image LC395 ); MNHN-IM-2019-8228 • 3 specimens, dead; Touho , vicinity of Baie de Touho, Stn 1251; 20°46.0′ S, 165°13.0′ E; depth 6–15 m; Sep. 1993; Expédition Montrouzier leg.; vase, sable, herbiers; MNHN-IM-2000-38865 • 3 specimens, living; Nouméa , off Nouville, Stn 1345; 22°16.1′ S, 166°23.7′ E; depth 15 m; 1 Oct. 1992; P. Bouchet leg.; sable grossier sous vase limoneuse, herbiers; MNHN-IM-2000-38866 .

Other material

NEW CALEDONIA – Grande Terre, Koumac • 1 specimen, dead; Stn KD539; 20°34.1′ S, 164°10.6′ E; depth 11 m; 6 Nov. 2019; KOUMAC 2.3 leg.; algues brunes, éponges; MNHN • 1 specimen, dead; Stn KD556; 20°32.9′ S, 164°12.2′ E; depth 5–6 m; 11 Nov. 2019; KOUMAC 2.3 leg.; sable gris; MNHN • 2 specimens, dead; lagoon between the land and l’Infernet, Stn 1299; 20°34.4′ S, 164°13.0′ E; depth 12– 14 m; Oct. 1993; Expédition Montrouzier leg.; slabs with gorgonians, silt; MNHN • 1 specimen, dead; Passe Deverd, Stn 1321; 20°44.7′ S, 164°14.9′ E; depth 90–115 m; Oct. 1993; Expédition Montrouzier leg.; muddy sand; MNHN • 8 specimens, dead; lagoon between the land and l’Infernet, Stn 1300; 20°35.6′ S, 164°15.2′ E; depth 10–11 m; Oct. 1993; Expédition Montrouzier leg.; sable gris vaseux; MNHN • 1 specimen, dead; Stn KD505; 20°34.3′ S, 164°15.2′ E; depth 2–4 m; 29 Oct. 2019; KOUMAC 2.3 leg.; sablo-vaseux coquillé; MNHN • 14 specimens, dead; Stn KD501; 20°36.2′ S, 164°15.2′ E; depth 11 m; 28 Oct. 2019; KOUMAC 2.3 leg.; vase; MNHN • 14 specimens, living; channel of the Passe de Koumac, Stn 1314; 20°39.8′ S, 164°15.3′ E; depth 30–63 m; Oct. 1993; Expédition Montrouzier leg.; sable coquillier vaseux; MNHN • 1 specimen, dead; Stn KD525; 20°36.7′ S, 164°15.3′ E; depth 12 m; 3 Nov. 2019; KOUMAC 2.3 leg.; vase dense; MNHN • 50+ specimens, dead; channel of the Passe de Koumac, Stn 1313; 20°38.8′ S, 164°15.6′ E; depth 33–38 m; Oct. 1993; Expédition Montrouzier leg.; vase à turritelles; MNHN • 10 specimens, dead; Stn KD503; 20°36.6′ S, 164°15.9′ E; depth 8 m; 28 Oct. 2019; KOUMAC 2.3 leg.; sablo-vaseux; MNHN • 1 specimen, dead; Stn KD575; 20°38.9′ S, 164°15.8′ E; depth 35 m; 19 Nov. 2019; KOUMAC 2.3 leg.; vase; MNHN • 3 specimens, dead; Stn KD504; 20°34.7′ S, 164°16′ E; depth 4–5 m; 29 Oct. 2019; KOUMAC 2.3 leg.; vase et coquilles; MNHN • 2 specimens, dead; Stn KD508; 20°37.8′ S, 164°16.4′ E; depth 16 m; 30 Oct. 2019; vase; MNHN • 1 specimen, dead; Stn KD578; 20°43.8′ S, 164°16.4′ E; depth 11–12 m; 19 Nov. 2019; KOUMAC 2.3 leg.; sable fin gris à Halophila ; MNHN • 9 specimens, dead; Stn KD545; 20°40.2′ S, 164°16.6′ E; depth 25 m; 8 Nov. 2019; KOUMAC 2.3 leg.; vase dense; MNHN • 8 specimens, dead; Stn KR1038; 20°40.5′ S, 164°17.7′ E; depth 13 m; 12 Nov. 2019; KOUMAC 2.3 leg.; sable vaseux à Caulerpa ; MNHN • 2 specimens, dead; Stn KD573; 20°44.5′ S, 164°18.4′ E; depth 25–27 m; 19 Nov. 2019; KOUMAC 2.3 leg.; vase; MNHN • 6 specimens, dead; Stn KD 512; 20°44.9′ S, 164°20.4′ E; depth 15–16 m; 31 Oct. 2019; KOUMAC 2.3 leg.; vase grise; MNHN. – Grande Terre , Touho • 1 specimen, dead; around the Thiem, Stn 1268; 20°45.2′ S, 165°08.0′ E; depth 9–11 m; Sep. 1993; Expédition Montrouzier leg.; sable fin; MNHN • 4 specimens, dead; Baie de Touho, Stn 1250; 20°46.7′ S, 165°13.7′ E; depth 3–6 m; Sep. 1993; Expédition Montrouzier leg.; sable vaseux; MNHN • 8 specimens, dead; channel NE of Banc de Touho, Stn 1260; 20°44′ S, 165°14′ E; depth 49–59 m; Sep.1993; Expédition Montrouzier leg.; sable coquillier; MNHN. – Grande Terre, Nouméa • ± 50 specimens, living; Nouméa, off Nouville, Stn 1345; 22°16.1′ S, 166°23.7′ E; depth 15 m; 1 Oct. 1992; P. Bouchet leg.; sable grossier sous vase limoneuse, herbiers; MNHN • 1 specimen, dead; channel Îlot Maître, Stn 1335; 22°19.7′ S, 166°26.6′ E; depth 20–24 m; 2 Dec. 1992; P. Bouchet, Campagne LAGON leg.; eunicid tubes with epibionts; MNHN. – Loyalty Islands • 1 specimen, dead; Lifou, Baie du Santal, off Peng, Stn 1443; 20°53.8′ S, 167°07.3′ E; depth 48–52 m; 14 Nov. 2000; Atelier LIFOU 2000 leg.; drop-off; MNHN .

FIJI • 1 specimen, dead; Viti Levu , west lagoon, Stn BS 43; 17°51.6′ S, 177°13.4′ E; depth 26 m; 19 Oct. 1998; NO Alis, SUVA 2 leg.; eunicid tubes with epibionts; MNHN .

Description ( Fig. 53 )

SHELL. Very small (adult diameter up to 2.3 mm), wider than high (H/D 0.62–0.70); spire low, whorls evenly rounded periphery at mid-whorl, suture strongly indented; sculpture predominantly of low, evenlyspaced, spiral cords; base rounded, widely umbilicate; teleoconch of up to 3.3 whorls. First teleoconch whorl with three fine spiral lirae, strengthening during second whorl and appearing more cord-like, increasing to 6–8 in number by intercalation of intermediaries; axial sculpture comprising close-set, microscopic axial threads with additional stronger, widely-spaced axial riblets producing regular netlike cancellation ( Fig. 54A ); riblets raised to form small nodules where they cross spiral cords; sculpture similar on subsequent whorls, but axial riblets less regularly spaced; basal sculpture similar, but cords thinner and more numerous towards and within umbilicus; umbilical rim evenly rounded, rendered weakly plicate by axial riblets. Aperture circular; peristome almost radial, briefly interrupted in parietal region; outer lip simple; interior nacreous.

COLOUR. Colour and pattern highly variable; ground colour ranging from dirty white to dark purplishbrown, variously mottled with darker and lighter spots, blotches and flames; pale specimens frequently with darker marks radiating from suture and with blotches at periphery; spiral cords commonly spotted with white, particularly below periphery; rare specimens with candy-stripe pattern ( Fig. 53I ); protoconch usually whitish or pale, occasionally almost black ( Fig. 53G ).

DIMENSIONS. Holotype, height 1.3 mm, diameter 2.0 mm; largest specimen, diameter 2.3 mm.

PROTOCONCH ( Fig. 54B ). Typically umboniine, diameter 160–180 µm; apical beak present and confluent with terminal lip; apical bulb sculptured with oblique threads crossed by subspiral threads; terminal lip weakly convex.

OPERCULUM ( Fig. 54C–D ). Corneous; multispiral with relatively narrow whorls; no spiral microsculpture evident; peripheral fringe rather broad, its radial striations remaining evident on earlier whorls.

RADULA ( Fig. 54E–F ). Formula ∞ +5+ 1+5+ ∞, ± 20 transverse rows of teeth; teeth in central field reduced to very thin, overlapping base-plates, inner ones with a mere vestige of shaft anteriorly; fifth lateral subquadrate. Transitional latero-marginal tooth not evident. Marginal teeth well developed with narrow shaft and strongly recurved cusp; cusps of inner marginal teeth ovate, with rounded central denticle and three progressively smaller, more pointed denticles on each side; marginal teeth progressively smaller toward radula margin and with more finely denticulate cusps.

EXTERNAL ANATOMY ( Fig. 55 ). Little detail evident in rehydrated specimens, but photographs of living animals indicate that the right eyestalk is larger than the left one.

Habitat

Mostly found as dead shells in mud and silt washed into lagoonal channels and passes, but living specimens associated with rather more sandy substrata; at depths of 1–90 m (living 1–30 m).

Distribution ( Fig. 56 )

Known from New Caledonia (Grande Terre and Lifou) and Fiji. A similar distribution to that of Ethalia lampra (above).

Remarks

Ethminolia durbanensis (Kilburn, 1977) from the south-western Indian Ocean has a similar profile, but it attains a much larger size (diameter ± 5.0 mm), has shouldered whorls and an angled and crenulate umbilical rim. Ethminolia probabilis Iredale, 1924 from south-eastern Australia is larger still (diameter up to 8.0 mm) and has distinctly shouldered whorls and more close-set spiral sculpture ( Fig. 78D–G ). Solariella pygmaea Poppe, Tagaro & Dekker, 2006 from the Philippines has a shell of similar overall facies and comparable size to that of E. hickmanae sp. nov., but it is much taller (H/D 0.95 vs <0.70). Referral of E. hickmanae to Ethminolia is provisional.

Figures

Fig. 53. Ethminolia hickmanae sp. nov. A–C. Holotype, Koumac, Stn KD561, height 1.3 mm diameter 2.0 mm (MNHN-IM-2000-38863). D–F. Dark specimen, Koumac, Stn KD530, height 1.2 mm, diameter 1.70 mm (paratype, MNHN-IM-2000-29842). G–I. Further colour variations, Nouméa, Stn 1345, diameters 1.70 mm, 1.66 mm and 1.65 mm, respectively (paratypes, MNHN-IM-2000-38866).

Fig. 54. Ethminolia hickmanae sp. nov. A. Oblique view of apex. B. Protoconch. C–D. Operculum. E–F. Radula. A–B. Koumac, Stn KD545. C–F. Nouméa, Stn 1345 (paratype, MNHN-IM-2000-38866). Scale bars: A, C =200 µm; B =50 µm; D–E=50 µm; F =10 µm.

Fig. 55. Ethminolia hickmanae sp. nov., living specimen, Koumac, Stn KD547, shell diameter ± 1.8 mm (paratype, MNHN-IM-2019-8228) (image LC395).

Fig. 56. Distribution of Ethminolia hickmanae sp. nov. Type locality indicated in pink.

Fig. 78. Specimens examined and illustrated for comparison. A–C. Holotype of Monilea pusilla A. Adams, 1853, provenance unknown, H. Cuming Collection (NHMUK 1968101), height 3.2 mm, diameter 4.0 mm. Images courtesy of Kevin Webb, NHM Photo Unit. © The Trustees of the Natural History Museum, London. D–G. Topotype of Ethminolia probabilis Iredale, 1924, Two-fold Bay, New South Wales, Australia, diameter 5.0 mm (NMW.1955.158).H–K. Syntype of Minolia henniana Melvill, 1891, Magnetic Island, Queensland, Australia, diameter 4.3 mm (NMW.1955.150.00117).