Limatium aureum, Strong, Ellen E. & Bouchet, Philippe, 2018

Strong, Ellen E. & Bouchet, Philippe, 2018, A rare and unusual new bittiine genus with two new species from the South Pacific (Cerithiidae, Gastropoda), ZooKeys 758, pp. 1-18 : 5-8

Limatium aureum sp. n. Fig. 3 A–H, K, L, N

Type material.

Holotype MNHN IM-2013-42460 (Fig. 3A); paratypes as listed below.

Type locality.

Austral Islands, Maria I., outer slope of barrier reef, 21°47.8'S, 154°43'W, 24 m [TUHAA PAE 2013 cruise, stn. AMA02, field number PB16_BC855; leg. A. Fedosov; 5 April 2013].

Other material examined

(all in MNHN uncatalogued, except where noted): FRENCH POLYNESIA. AUSTRAL IS: RAPA Island expedition 2002: Stn. 6, off Baie de Ahurei, 27°36.8'S, 144°16.7'W, 42 m, 1 dd. - Stn. 8, SE of Tauna islet, 27°36.5'S, 144°17.7'W, 52-57 m, 7 dd (MNHN IM-2014-6928, Fig. 3L). - Stn. 28, Pointe Taekateke, 27°38.4'S, 144°20.6'W, 30 m, 1 dd. - Stn. 36, Pointe Kauira, 27°33.5'S, 144°20.8'W, 27 m, 1 live collected (lv), 2 dd (MNHN IM-2014-6920, IM-2014-6929, Fig. 3B, N). - Stn. 44, NW of Tauna islet, 27°36.3'S, 144°18.2'W, 30 m, 2 dd (MNHN IM-2014-6923, Fig. 3E). - BENTHAUS stn. DW1934, Banc Président Thiers, 24°40.6'S, 145°57.4'W, 560-1150 m, 1 dd. TUAMOTU IS: Makemo, secteur Pohue, 16 °40.1'S, 143°22.5'W, 63 m, 1 dd, paratype USNM 1462727 ex coll. Letourneux; Makemo, passe Arikitamiro, ca. 16°37.1'S, 143°33.9'W, 45 m, 47 m and 54 m, 3 dd, in coll. Letourneux; Rangiroa, Passe de Tiputa, ca. 14°58.0'S, 147°37.5'W, 81 m and 100 m, 2 dd, USNM 1462728 ex coll. Letourneux. NEW CALEDONIA. Coral Sea. Lansdowne-Fairway Reefs. CORAIL 2 stn. DW26, 20°22'S, 161°05'E, 62 m, 1 lv (MNHN IM-2014-6921, Fig. 3C). - EBISCO stn. DW2622, 20°04'S, 160°21'E, 291-323 m, 1 dd. Mainland New Caledonia. LAGON Stn. 830, off Poindimié, 20°49'S, 165°19'E, 105-110 m, 4 dd. MONTROUZIER Stn. 1269, Récif Doiman off Touho, outer slope, 20°35.1'S, 165°08.1'E, 15-20 m, 4 dd. - Stn. 1331, Grand Récif de Koumac, outer slope, 20°40'-20°40.6'S, 164°11.2'-164°12.1'E, 55-57 m, 4 dd. - Stn. 1352, Grand Récif Aboré off Nouméa, outer slope, 22°22.2'S, 166°16.0/166°16.1'E, 27-35 m, 5 lv, 4 dd (MNHN IM-2014-6924, IM-2014-6927, Fig. 3F, K); - Stn. 1354, Grand Récif Aboré, outer slope, 22°22.3'S, 166°15.9'E, 27-37 m, 2 lv, 2 dd. BATHUS 1 stn. DW692, 20°35'S, 164°59'E, 140-150 m, 2 dd. LOYALTY ISLANDS: LIFOU 2000 Expedition, Baie du Santal: stn. 1418, 20°46.9'S, 167°07.9'E, 1-5 m, 1 dd (MNHN IM-2014-6926, Fig. 3H). - Stn. 1423, 20°54'S, 167°07.3'E, 12 m, 2 dd (MNHN IM-2014-6925, Fig. 3G). - Stn. 1429, 20°47.5'S, 167°07.1'E, 8-18 m, 2 dd. - Stn. 1432, 20°53.5'S, 167°02.7'E, 12-32 m, 2 dd. - Stn. 1434, 20°52.5'S, 167°08.1'E, 5-20 m, 2 dd. - Stn. 1441, 20°46.4'S, 167°02'E, 20 m, 2 dd. - Stn. 1442, 20°46.4'S, 167°02'E, 47 m, 1 dd. - Stn. 1443, 20°53.8'S, 167°07.3'E, 48-52 m, 3 dd. - Stn. 1445, 20°50.8'S, 167°09.7'E, 10-12 m, 1 dd. - Stn. 1448, 20°45.8'S, 167°01.6'E, 20 m, 4 dd. - Stn. 1449, 20°45.8'S, 167°01.6'E, 17 m, 1 dd. - Stn. 1450, 20°45.8'S, 167°01.6'E, 27-31 m, 1 dd. - Stn. 1451, 20°47.3'S, 167°06.8'E, 10-21 m, 3 dd. - Stn. 1453, 20°54.6'S, 167°02.1'E, 21-30 m, 1 dd. - Stn. 1454, 20°56.6'S, 167°02'E, 15-18 m, 2 dd. - Stn. 1455, 20°56.8'S, 167°02.7'E, 15-20 m, 1 lv, 1 dd. - Stn. 1456, 20°49.3'S, 167°10.4'E, 25-30 m, 1 lv, 1 dd. - Stn. 1457, 20°46.8'S, 167°02.8'E, 5-10 m, 2 lv, 1 dd. - Stn. 1461, 20°54'S, 167°02'E, 100-120 m, 1 lv, 1 dd. - Stn. 1469, 20°54.2'S, 167°00.4'E, 70-130 m, 2 dd.

Etymology.

Latin adjective aureus, -a, -um, meaning golden, with reference to the background color of the shell.

Diagnosis.

Shell [holotype, unless otherwise noted]. Shell short, squat, with regular, conical spire, body whorl occupying ~46% of shell height, consisting of 9+ [tip of teleoconch and protoconch missing] rather flat teleoconch whorls, suture impressed (Fig. 3A). Protoconch [description based on specimens illustrated in Fig. 3K, L] multispiral, of 2.5 whorls, with a complex sculpture of two strongly pustulose, thick and heavy spiral keels at periphery, and a third, much lighter cord on the base, partly covered by next whorl; strong, prosocline, axial riblets on sutural ramp, fading out abapically towards spiral keel; and irregular, short, elongated or rounded granules that cover the abapical part of the whorl and may extend in between the two peripheral keels; protoconch/teleoconch transition sharp, with a lamellar terminal varix and a deeply indented sinusigera notch (Fig. 3K, L). On early teleoconch whorls sculpture consisting of closely-set axial ribs intersected by three spiral cords together forming beaded intersections, abapicalmost cord stronger, forming an angular projection at intersection with ribs; axial and spiral sculpture becoming weaker on exposed parts of subadult and adult whorls, until an almost smooth last whorl; last whorl with weakly defined basal cord encircling convex base bearing six well defined, raised cords. Siphonal canal very short, broadly open, not constricted. Aperture circular-ovate, ~32% of shell height. Anal canal indistinct. Columella concave with very thinly callused columellar lip. Outer lip of aperture slightly thickened, but not forming a terminal varix, subvertical on periphery, regularly convex on base. Shell surface smooth and shiny, as if waxed, color overall rich honey to golden brown with broad, opaque, irregular white fascioles extending from suture to suture at irregular intervals; adapical and basal cords with alternating white and honey blotches at regular intervals; columellar side of anal and columellar callosity white, parietal callosity transparent. Tip of teleoconch (first whorl) white, protoconch dark brown. Dimensions: 7.97 × 3.40 mm. Average 6.83 ± 1.47 mm (n = 12).

Operculum. Subcircular, paucispiral, comprising three whorls. Nucleus large, subcentral, ~72% of operculum length.

Radula. Rachidian (Fig. 4 A–C, E, F) with roughly hexagonal to septagonal basal plate, squarish to rectangular, broader than tall, with elevated central portion with rounded, U-shaped lower margin. Cutting edge bearing one strong central and two lateral long, dagger-like pointed cusps; central cusp up to twice as long as lateral cusps. Lateral teeth (Fig. 4A, B, C, E–F) with short lateral extensions, roughly 1.5 times length of cutting edge. Cutting edge with large central, pointed cusp and single, large pointed inner cusp and two to four tapering outer denticles. Thickened buttress extending down face of marginal tooth slightly outside central cusp, terminating in prominent, bluntly rounded peg roughly halfway down face (Fig. 4F). Marginal teeth (Fig. 4A, C–D, E) similar in shape and denticulation. Inner marginal teeth with large pointed central cusp, two to three tapering inner pointed cusps and one to two outer pointed denticles. Outer marginal teeth with large, pointed, central cusp, two to three tapering inner pointed cusps and a smooth, acuspate outer edge.

Distribution and ecology.

Austral Islands and Tuamotus (French Polynesia); Loyalty Islands, mainland New Caledonia, and Coral Sea. Known only from the material examined. Collected alive in 10-100 m, empty shells to 560-1150 m were undoubtedly carried downslope.

Remarks.

The holotype is “untypical” in the sense that it is an unusually broad specimen that, however, seems to be connected by morphologically intermediate specimens to forms that are more slender and with a strong cord delimiting the basal disc. All these specimens share a color pattern of alternating white and honey blotches on the subsutural and basal cords, in addition to ill-defined axial white fascioles, on an overall rich, golden honey background. Another type of variation comes from the extension/persistence of the spiral cords on subadult/adult whorls - with specimens almost completely smooth on the periphery of the last whorl and others with strong spiral cords persisting onto the last whorl.

An empty shell collected from Tonga (BORDAU 2 stn. DW1512, between Eua and Tongatapu, 21°19'S, 175°01'W, 183-184 m) (MNHN IM-2014-6922, Fig. 3D) is unusually tall and narrow, with spiral and axial sculpture persisting onto the last whorl; its color pattern, however, is very similar to that of L. aureum and we tentatively consider it to belong to that species.