Xanthodaphne araneosa ( Watson, 1881 )

Figueira, Raquel Medeiros Andrade & Absalão, Ricardo Silva, 2012, Deep-water Raphitomidae (Mollusca, Gastropoda, Conoidea) from the Campos Basin, southeast Brazil, Zootaxa 3527, pp. 1-27 : 11

Xanthodaphne araneosa ( Watson, 1881)

( Figs. 14–15 )

Pleurotoma (Defrancia) araneosa Watson, 1881: 462 .

Clathurella araneosa ( Watson, 1881) : Watson (1886, 355, pl. 19, fig. 1).

Type material: Syntypes BMNH 1887.2.9.1105, BMNH 1986122

Type locality: Challenger sta. 24 (18°38’30”N, 65°05’30”W), north of Culebra Island, Puerto Rico, West Indies, 713 m.

Material examined: 18533 [1] OP I # 58; 18534 [3] OP I # 63; 18535 [1] OP I # 71; 18536 [1] OP I # 80; 18537 [1] OP II # 53; 18538 [1] OP II # 77.

Description: Shell short, plump, white, up to 5.18 mm long. Protoconch with about 4.5 whorls, yellowish. Protoconch 1 with rows of tiny crosses. Protoconch 2 with diagonal cancellation on the lower 2/3 of the whorls and axial riblets on the upper 1/3, mostly vanished on the last two whorls. Clear-cut proto-teleoconch boundary. Teleoconch whorls with a gentle shoulder, demarcated by a thin but sharp spiral cord. Subsutural zone with curved thin axial riblets, and many sharp opisthocline axial ribs below it that vanish toward the base. Suture very shallow. Base moderately short and slightly concave. Fasciolar region with about five oblique and very faint cords. Anal sinus shallow and wide. Outer lip thin. Anterior siphonal canal broad and short. Aperture elliptical.

Geographic distribution: Northwest Atlantic: Puerto Rico ( Watson, 1881; Watson, 1886). Southwest Atlantic: Campos Basin, Rio de Janeiro (this paper). Bathymetry: 713 m ( Watson, 1881)– 1950 m (this paper).

Discussion: This species can be distinguished from any other Western Atlantic species of Xanthodaphne by the presence of a thin spiral cord on the whorl shoulder and by the sharp opisthocline axial ribs. The most similar species is Xanthodaphne n. sp. ( Bouchet & Warén, 1980: 66, fig. 138) from the eastern Atlantic. However, these species can be easily distinguished by their protoconch: in Xanthodaphne n. sp. ( Bouchet & Warén, 1980: 99, fig. 235) the whorls are entirely reticulated, whereas X. araneosa has diagonal cancellation on the lower 2/3 of the whorls and axial riblets on the upper 1/3. In addition, X. araneosa has sharp opisthocline axial ribs, whereas Xanthodaphne n. sp. has gentle, somewhat sinuous axial threads.

Xanthodaphne araneosa is reported for the first time in South Atlantic waters. It was previously known to occur only in Puerto Rico. Its bathymetric range is also increased. The only depth previously reported for this species was 713 m ( Watson, 1881) and it has now been found at depths from 1050 to 1950 m.

Figures

FIGURES 12 – 19. 12, 13 — Xanthodaphne dalmasi Dautzenberg & Fischer, 1896, IBUFRJ 18498; 12 — 4.94 mm, whole shell; 13 — protoconch; 14, 15 — Xanthodaphne araneosa Watson, 1881, IBUFRJ 18537; 14 — 5.18 mm, whole shell; 15 — protoconch; 16, 17, 18, 19 — Xanthodaphne pichi n. sp.; 16, 18, 19 — Holotype MNRJ 30289; 16 — 3.88 mm, whole shell; 18 — detail of shell surface; 19 — protoconch; 17 — Paratype IBUFRJ 17063, 6.98 mm, whole shell. Scale bars: 12, 15 and 16 = 500 μm; 13 and 19 = 300 μm; 14 and 16 = 1 mm; 18 = 50 μm.