Gymnobela bairdii ( Verrill & Smith, 1884 )

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 : 18

Gymnobela bairdii ( Verrill & Smith, 1884)

( Figs. 29–30 )

Pleurotomella bairdii Verrill & Smith, 1884 in Verrill, 1884: 147, pl. 31, fig. 1: Abbott (1974: 289, ind. 3434).

Type material: Syntypes YPM IZ 0 14903, YPM IZ 0 14904, YPM IZ 0 15716, YPM IZ 0 15717, YPM IZ 0 15718.

Type locality: Off New Jersey, USA. Sta. 2037 (38º53’00”N, 69º23’30”W, 3147 m); Sta. 2038 (38º30’30”N, 69º08’25”W, 3718 m); Sta. 2041 (39º22’50”N, 68º25’W, 2940 m); Sta. 2097 (37º56’20”N, 70º57’30”W, 3505 m); Sta. 2098 (37º40’30”N, 70º37’30”W, 4061 m).

Material examined: 18950 [1] OP I # 52; 18951 [2] OP I # 62; 18952 [5] OP I # 75; 18953 [1] OP I # 80; 18954 [1] OP I # 45; 18955 [1] OP II # 47; 18956 [2] OP II # 52; 18957 [1] OP II # 58; 18958 [4] OP II # 61; 18959 [2] OP II # 62; 18960 [4] OP II # 83; 15359 [2] OP I # 74; 16809 [1] OP II # 79; 16507 [2] OP I # 5; 16689 [2] OP I # 9; 16472 [2] OP I # 10; 16474 [1] OP I # 11; 16492 [1] OP I # 12; 16470 [3] OP I # 13; 16437 [4] OP I # 16; 16461 [2] OP I # 18; 16552 [1] OP II # 2-1; 16610 [1] OP II # 5-1; 16575 [1] OP II # 10; 16519 [3] OP II # 11-1; 16675 [4] OP II # 13-1; 16637 [2] OP II # 13-2; 16742 [9] OP II # 16-1; 16645 [1] OP II # 17-1.

Description: Shell plump, biconical, yellowish, up to 25.74 mm long. Protoconch with about four whorls. Protoconch 1 with spiral rows of tiny crosses. Protoconch 2 with diagonal cancellation on the lower 2/3 of the whorls and arched axial riblets. Clear-cut proto-teleoconch boundary. Teleoconch whorls with a low-set shoulder forming a pagoda-like profile. Short axial riblets form a region below the suture. Numerous opisthocline axial ribs form a soft nodulation on the whorl shoulder. Shell surface covered by spiral rows of minute granules. Suture moderately shallow. Base medium-sized with axial ribs reaching the aperture but becoming weaker toward it. Anal sinus not discernible. Inner lip thin and reflected over parietal wall. Outer lip thin. Anterior siphonal canal moderately short, wide and slightly inflected. Aperture elliptical.

Geographic distribution: Northwest Atlantic: New Jersey, USA ( Verrill, 1884). Southwest Atlantic: Campos Basin, Rio de Janeiro (this paper). Bathymetry: 750 m (this paper)– 4061 m ( Verrill, 1884).

Discussion: Our material generally matches well with the original illustration ( Verrill, 1884: pl. XXXI, fig. 1), but differs from it in having a shoulder that is positioned on the lower half of the whorl. In G. bairdii , the shoulder is on the upper half. Also, in our material the whorls are wider and shorter than in G. bairdii .

Gymnobela bairdii is reported for the first time in South Atlantic waters (21–22ºS). It was previously known to occur only in the United States (37–39ºN). Its bathymetric range is also increased. The shallowest depth previously reported was 2940 m ( Verrill, 1884) and it has now been found at depths from 750 to 1970 m.

Figures

FIGURES 27 – 37. 27, 28 — Gymnobela atypha (Bush, 1893); 27 — IBUFRJ 16571, 20.42 mm, whole shell; 28 — IBUFRJ 18924, protoconch. Figures 29, 30 — Gymnobela bairdii (Verrill & Smith, 1884); 29 — IBUFRJ 16437, 22.48 mm, whole shell; 30 — IBUFRJ 18950, protoconch. Figures 31, 32 — Gymnobela chyta (Watson, 1881); 31 — IBUFRJ 16421, 31.54 mm, whole shell; 32 — IBUFRJ 19178, protoconch. Figures 33, 34 — Gymnobela xaioca n. sp.; 33 — Holotype MNRJ 30287, 20.94 mm, whole shell; 34 — Paratype IBUFRJ 16460, 14.34 mm, whole shell. Figures 35, 36 — Gymnobela blakeana Dall, 1881; 35 — IBUFRJ 16574, 10.02 mm, whole shell; 36 — Syntype USNM 87427. Figure 37 — Gymnobela aquilarum Watson, 1881, Holotype BMNH 1887.2. 9.724. Scale bars: 27 and 29 = 3 mm; 28, 30 and 32 = 300 μm; 31 and 33 = 4 mm; 34, 35, 36 and 37 = 2 mm.