Hadroconus altus Watson 1879

Hadroconus altus (Watson, 1879)

(Figs. 9–12)

Synonymy see Quinn (1987). Complement:

Hadroconus altus: Quinn, 1987: 62 (figs. 1–5); Rios, 1994: 45 (pl. 14, fig. 155); Rios, 2009: 73 (textfig.); Benkendorfer & Soares-Gomes, 2009: 151; Rosenberg et al., 2009: 622.

Type locality: NW of St. Thomas, Virgin Islands, Challenger station 24, 18°30’30’’N 65°05’30’’W, 713 m (Quinn 1987).

Distribution: Western Atlantic Ocean, from Texas, USA, to NE Brazil, 500–2360 m depth (Quinn 1987; Rios 2009; Rosenberg et al. 2009).

New occurrence: Southeastern Brazil, from Espírito Santo to Rio de Janeiro, 610–4192 m depth.

Brief description: Shell small, conical (1.2 times as wide as tall), carinated, relatively thick-walled. Color iridescent under homogeneous white to cream porcelaneous layer. Protoconch (~1 whorl), smooth, prominent, rounded; transition indistinct. Teleoconch sculptured by 12–15 spiral threads, usually more conspicuous near suture; threads near suture presenting strong, axially elongated nodules, expanding to middle portion of whorls in different degrees, forming faint, sinuous axial ribs in some specimens. Sculpture on adapical portion of body whorl similar to that on opposite side, without nodules. Whorls slightly convex, becoming somewhat concave near suture. Aperture rectangular, acuminate toward carina, with weakly demarcated columellar tooth. Umbilicus wide (1/4–1/ 5 of shell diameter), deep; umbilical periphery angular, bearing strong nodules.

Measurements (in mm): 7½ –8½ whorls, H = 5.3 ± 0.38, D = 6.55 ± 0.22, h = 1.5 ± 0.22, d = 2.45 ± 0.29.

Material examined: Brazil: Espírito Santo: off São Mateus, continental slope of Abrolhos, 18°55’S 37°49’W, 1200–1500 m, MNHN, 1 shell, (MD55, sta. CP68, 26/v/1987); 18°58’S 37°48’W, 682 m, MNHN, 2 shells, (MD55, sta. SY74, 27/v/1987); 18°58’S 37°49’W, 637 m, MNHN, 4 shells, (MD55, sta. CB76, 27/v/1987); 18°59’S 37°47’W, 1540–1550 m, MNHN, 10 shells, MZSP 116281, 3 shells (MD55, sta. DC70, 26/v/1987); 19°00’S 37°48’W, 950–1050 m, MNHN, 8 shells, MZSP 116284, 5 shells, (MD55, sta. DC72, 27/v/1987); 19°01’S 37°47’W, 1500–1575 m, MNHN, 3 shells, MZSP 116283, 2 shells (MD55, sta. CB79, 28/v/1987); 19°40’S 37°48’W, 790–940 m, MNHN, 15 shells, MZSP 116282, 3 shells (MD55, sta. CB77, 27/v/1987); off Linhares, N of Dogaressa Bank, 20°02’S 33°27’W, 4185–4192 m, MNHN, 2 shells, (MD55, sta. CP62, 23/v/1987); Rio de Janeiro: E of Cabo de São Tomé, 21°25’S 39°56’W, 1400–1420 m, MNHN, 2 shells, (MD55, sta. DS05, 09/v/ 1987); 21°36’S 39°58’W, 1190–1205 m, MNHN, 5 shells, MZSP 116287, 3 shells (MD55, sta. CB99, 23/v/1987); S of Cabo Frio, 23°46’S 42°10’W, 610 m, MNHN, 1 shell, (MD55, sta. CB105, 02/vi/1987); 23°54’S 42°10’W, 830 m, MNHN, 1 shell, (MD55, sta. CB106, 02/vi/1987); 24°00’S 42°14’W, 1020 m, MNHN, 6 shells, MZSP 116286, 3 shells (MD55, sta. CB107, 02/vi/1987).

Remarks: The present specimens compare well with Hadroconus altus, a well-known species from the North Atlantic. This species shows a high degree of conchological variation in overall shell shape and sculpture (Quinn 1987), which can also be seen in the present material. The new records extend the distribution of H. altus ca. 1,700 km to the south, and its bathymetric range ca. 2,000 m, down to 4,192 m.