Turbonilla krakstadi, Lygre, Frøydis & Schander, Christoffer, 2010

Lygre, Frøydis & Schander, Christoffer, 2010, Six new species of pyramidellids (Mollusca, Gastropoda, Pyramidelloidea) from West Africa, introducing the new genus Kongsrudia, Zootaxa 2657, pp. 1-17 : 7-8

Turbonilla krakstadi new species

(Fig. 4 A–E)

Type locality: Gabon station G11, 02 º 40’S, 09º 14’E, 90 m.

Type specimens: Holotype, Bergen Museum ZMBN 86657. One paratype Bergen Museum ZMBN 86658. One paratype Gothenburg Natural History Museum GNM Gen. kat. 2010-22.254.

Material examined: Type material.

Etymology: The species is named in honor of Jens Otto Krakstad, who has lead many of the expeditions where the material included in this study was collected, and was fundamental in the initiative of getting a benthic part of the surveys.

Description: Shell small, slender, conical, milky white and shiny with blunt apex. Protoconch of type A- II, small and protruding. Whorls almost straight, bending slightly towards the lower suture, turetted. Suture distinct but not deep, noticeably oblique. Subsutural shelf present and distinct. Axial ribs elevated, strong and shouldered, irregular, almost straight and opisthocline. Interspaces equally broad or broader than ribs. Ribs ending abruptly at the periphery of the ultimate whorl or continuing to the base. If continuing to the base, they are more diffuse below the ultimate whorl. No spiral sculpture present. Aperture subrectangular. No collumellar tooth and no umbilicus.

Distribution: Gabon, 61- 90 m.

Remarks: The size of the protoconch differ slightly in the two shells from station G11. The interspaces between the ribs also differ slightly and one shell has ribs closer together. Turbonilla perezdionisi Peñas & Rolan, 1997 resembles this species, but has straighter whorls and lacks the subsutural shelf and shouldered axial ribs. The ribs of T. perezdionisi are also more sinuous and less opistocline than in T. krakstadi . Turbonilla melvilli Dautzenberg, 1912 shows some resemblance to T. krakstadi , but only the initial whorls are turreted in this species and the axial ribs are more tightly spaced. Turbonilla gradata Bucquoy, Dautzenberg & Dollfus, 1883 has more regular axial ribs and is less turreted than T. krakstadi .

FIGURE 4 A–E. Turbonilla krakstadi n. sp. A: Holotype, teleoconch, station G11, Gabon, 02º40’S, 09º14’E; B: Paratype, teleoconch, station G3, Gabon, 00º05’N, 09º02’E; C-D: Paratype, protoconch, station G11, Gabon, 02º40’S, 09º14’E; E: Paratype, details of the subsutural shelf, station G11, Gabon, 02º40’S, 09º14’E.