Gymnobela bairdii Verrill & Smith 1884

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.