Turbonilla nanseni, Lygre & Kongsrud & Schander, 2011

Lygre, Frøydis, Kongsrud, Jon Anders & Schander, Christoffer, 2011, Four new species of Turbonilla (Gastropoda, Pyramidellimorpha, Turbonillidae) from the Gulf of Guinea, West Africa, African Invertebrates 52 (2), pp. 243-243 : 247

Turbonilla nanseni sp. n.

Fig. 2

Etymology: This species is named in honour of the research vessel R/V Dr Fridtjof Nansen, used for the collection of all the material used in this study (http://www.imr. no/om_havforskningsinstituttet/fasiliteter/fartoy/dr._fridtjof_nansen/en).

Diagnosis: Tall, high spired with large protoconch, convex whorls, and strong axial ribs crossed by microstriae.

Description: Shell tall, slender, conical towards subcylindrical, milky white and shiny with rounded apex. Protoconch of type A-II, diameter 380 μm, protruding nucleus. Teleoconch whorls slightly convex. Suture incised, not deep, slightly undulating, noticeably oblique. Axial ribs not very elevated, thin, straight or slightly curved, opisthocline; closely set, broader than interspaces; disappearing at periphery of ultimate whorl. Base smooth. Microsculpture of undulating spiral striae in interspaces and on ribs. Aperture subrectangular. Inner lip slightly folded. Columellar tooth absent. No umbilicus.

Holotype: GABON:station G16, 03°49'S: 10°37'E,- 69m ( ZMBN86948 ).Length 2.42mm,width0.6247 mm . Paratypes: Two from type locality in ZMBN (86949, 86950) . One in NMSA ( L8456 / T2747 ) .

Distribution: Nigeria and Gabon, - 63– 69 m.

Comparison: Turbonilla fulgidula ( Jeffreys, 1884) shows some resemblance to T. nanseni , but the whorls are slightly straighter in this species, and it has a subsutural shelf. The axial ribs have broader interspaces and are less opisthocline. T. pseudomarteli Peñas & Rolán, 1997 has a subsutural shelf and broader, more diffuse axial ribs. T. bengoensis Peñas & Rolán, 1997 has a smaller and more submerged protoconch, the whorls are slightly straighter and the axial ribs have broader interspaces.

Figures

Fig.2. Turbonilla nanseni sp. n.: (A) holotype; (B) paratype, teleoconch, station G16, Gabon; (C) holotype, protoconch; (D) paratype, protoconch, station G16, Gabon; (E, F) holotype, details of sculpture.