Pseudosetia azorica Bouchet and Warén, 1993

Gofas, Serge, 2007, Rissoidae (Mollusca: Gastropoda) from northeast Atlantic seamounts, Journal of Natural History 41 (13 - 16), pp. 779-885 : 816-818

Pseudosetia azorica Bouchet and Warén, 1993

( Figure 20 )

Pseudosetia azorica Bouchet and Warén 1993, p 686 , 689–690.

Type material

Holotype from Bartlett sta. 2, in ZMC (GAS-120), paratype in MNHN.

Type locality

Off Faial / Pico , the Azores (37 ° 13.89N, 28 ° 44.59W, 480 m) .

Material examined

Meteor— Seamount 2 DW152, 1 sh. (1.95× 1.20 mm). Hyères— Seamount 2 DW182, 4 spm.+122 sh. (1.47×1.0 to 2.05× 1.25 mm). Cruiser— Seamount 2 sta. DW237, 68 sh. (1.62×1.10 to 2.02× 1.20 mm); DW238, 2 sh. (1.98×1.22 to 2.08× 1.38 mm). Atlantis— Seamount 2 sta. DW255, 33 sh. (1.30×0.85 to 1.77× 1.07 mm); DW258, 10 sh. (1.42×0.96 to 1.60×1.00 mm); DW261, 11 sh. (1.70×1.20 to 2.10× 1.36 mm); DW263, 152 sh. (jv. 1.1× 0.82 mm; 1.45×1.00 to 2.15× 1.30 mm); TS270, 2 spm. (jv. 1.36×0.92 and 1.40×1.00 mm) and 12 sh. (jv. 0.80×0.67 to 1.45× 0.90 mm); DW274, 13 sh. (1.38×0.82 to 1.64× 1.06 mm).

Description

Shell with moderately high spire, up to 2.15× 1.30 mm. Protoconch of 1.5 convex whorls; surface of nucleus smooth, then with blurry bands of granules, finally with widely separated, indistinct spiral threads. Teleoconch of two to three moderately convex whorls, with a faint sculpture of weak axial lines, minute spiral striae and spiral cords. Axial lines irregular, in the form of wrinkles parallel to growth stages, fading out on the abapical part of the body whorl. Spiral striae more distinct on the adapical part of the whorl next to the suture. One spiral cord running along the suture or very close to it on the abapical side of the spire whorls; body whorl with this cord continued and with five to six more on the periumbilical area, separated by very broad interspaces, and decreasing in size towards the abapical side. Body whorl with an indistinct keel in prolongation of the suture. Outer lip orthocline, with a thin, flaring edge, thickened externally at a distance of the edge by a broad rim on which the spiral sculpture is attenuated; smooth and not thickened inside. Inner lip thin, quite appressed or leaving an extremely narrow umbilical chink. Shell colour entirely white, translucent. Operculum thin, paucispiral, with eccentric nucleus.

Remarks

Pseudosetia azorica was described from only five shells collected around the Azores, but is not rare on Atlantis seamount. Warén and Bouchet (2001) reported three specimens of Pseudosetia azorica on the North Atlantic ridge in 860–870 m depth .

It is distinguished from Pseudosetia amydralox and from Pusullina fuscapex n. sp. by having strong, definite spirals on the abapical surface. The latter species is found sympatrically on Meteor, Hyères, and Atlantis. Specimens found in deeper water on Cruiser seamount ( Figure 20D, E ) differ in having more convex whorls and a more distinct sculpture on spire whorls, reminiscent of that seen in Alvania stenolopha (see Figure 17A–C ). The protoconch sculpture is also very similar, suggesting that this species may be actually related to A. stenolopha despite the lack of axial sculpture. This relationship, if verified, would make Pseudosetia polyphyletic and call for a reassignment of the species.

Figures

Figure 17. (A, B) Alvania stenolopha Bouchet and Warén, 1993, shells from Atlantis seamount, DW261 (1340 m), actual size 2.12 and 2.02 mm; (C) protoconch of a juvenile shell, same locality; (D) detail of microsculpture, same shell as (A); (E) Alvania macella n. sp., holotype (sh.) from Atlantis seamount, DW261, actual size 2.04 mm; (F) paratype (sh.), same locality, actual size 2.10 mm; (G) protoconch of the same paratype; (H) detail of microsculpture of the holotype. Scale bars: 100 Mm.

Figure 20. Pseudosetia azorica Bouchet and Warén, 1993. (A, B) Shells from Atlantis seamount, DW255 (340 m), actual size 1.57 and 1.50 mm; (C) protoconch, juvenile specimen from Atlantis seamount, TS270 (330 m); (D) shell from Cruiser seamount, DW237 (670 m), actual size 1.62 mm; (E) protoconch, same shell. Scale bars: 100 Mm.