Mareleptopoma intermedia, Renard & Bouchet, 2003

Renard, Jacques Le & Bouchet, Philippe, 2003, New species and genera of the family Pickworthiidae (Mollusca, Caenogastropoda), Zoosystema 25 (4), pp. 569-591 : 577-578

Mareleptopoma intermedia n. sp.

( Fig. 5 ) TYPE MATERIAL. — Holotype (dd) and 4 paratypes in BPBM. TYPE LOCALITY. — Fanning I., Line Islands , Central Pacific.

ETYMOLOGY. — The specific name reflects the intermediate position of this species, which blends the characters of a teleoconch of M. iredalei with a protoconch of M. drivasi n. sp.

MATERIAL EXAMINED. — A total of 7 specimens (4 lots).

Line Islands. Fanning I., leg. Kay, 3 dd (holotype and 2 paratypes).

Micronesia. Ponape, barrier reef, mid pass, among Acropora, 1964 , leg. Kay, 2 dd (paratypes).

Lord Howe Island. Dredged, 1 dd ( AMS 059754 ex coll. Bell). — HMAS Kimbla , stn LH1, off Lord Howe I., 31°34.9’S, 159°03’E, 73 m, calcareous Lithothamnium nodules, 1976, leg. Ponder, Lowry & Rowe, 1 dd ( AMS 154749).

DISTRIBUTION. — Pacific Ocean: Line Islands, Ponape, Lord Howe.

DESCRIPTION

Holotype ( Fig. 5 ). Shell very small, rissoiform. Protoconch ( Fig. 5C ) consisting of 1.5 smooth globular whorls, indicating a non-planktotrophic larval development. Teleoconch with 3.5 whorls; spire conical; whorls with flat profile, separated by deep sutural groove with slightly granulated thread inside. On first teleoconch whorl, sculpture initially consisting of two beaded cords; anterior cord rapidly strengthening into prominent rounded keel, on abapical third of whorl. This keel separated from sutural cord by simple groove, and bearing rounded tubercles (about 18 per whorl). Adapical cord soon developing into coronate shoulder. Nodes of two spiral cords linked by faint prosocline costae; adult sculpture thus appearing regularly decussated. Body whorl occupying 68% of total height, with overall evenly curved outline, not angulated by main keel. Sutural cord developing around base into strong cord, with tubercles prolongating axial costae. Slightly convex base, showing two contiguous weaker cords; exterior cord also beaded, separated from peripheral cord by groove; inner cord forming somewhat irregular pad, winding around imperceptible umbilical slit. Subcircular aperture flaring into simple rim; rim slightly prominent over peristomal plane. Thick peristome surrounding aperture completely; outer lip not strongly prominent, clearly prosocline.

Dimensions

H = 1.3 mm, D = 0.8 mm.

REMARKS

Mareleptopoma intermedia n. sp. shares with M. drivasi n. sp. and M. pellucens n. sp. a smooth, non-planktotrophic protoconch. From the latter it can be distinguished by its strong sculpture, its less slender shape and its less extensive peristome. From M. drivasi n. sp., it differs primarily in its sculpture, with more prosocline and more nodulose ribs, two much stronger cords on the base, its reduced umbilical slit, and its narrower aperture. Mareleptopoma intermedia n. sp. also resembles more superficially Mareleptopoma iredalei , Sansonia sumatrensis ( Thiele, 1925) , or Reynellona bollandi n. sp. ( Fig. 10 ), from which it differs, among other characters, by its paucispiral, rather than multispiral, protoconch. Mareleptopoma appears to be the most appropriate genus for the present species (and for the other elongate species just cited), although it may appear to differ morphologically from the type species.

Figures

FIG. 5. — Mareleptopoma intermedia n. sp., holotype, Fanning, Line Islands (BPBM), H = 1.3 mm; A, B, apertural and side views; C, protoconch. Scale bar: C, 100 µm.

FIG. 10. — Reynellona borbonica n. sp., La Réunion, Marion-Dufresne, cruise MD 32, stn DR47 (MNHN); A, B, holotype, H = 3.1 mm; C, paratype, protoconch. Scale bar: C, 100 µm.