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.