Seguenzia formosa Jeffreys 1876

Seguenzia formosa Jeffreys, 1876

(Figs. 22–24)

Seguenzia formosa Jeffreys, 1876: 200; Jeffreys, 1885: 42; Quinn, 1983b: 728 (figs. 6, 17, 23). Seguenzia lineata: Rios, 2009: 72 (textfig.).

Seguenzia monocingulata: Marshall, 1983: 236; Rios, 1985: 33 (pl. 14, fig. 141); Gofas et al., 2001: 184. Seguenzia hapala: Rios, 1985: 33 (pl. 14, fig. 140); Rios, 1994: 44 (pl. 14, fig. 151); Rios, 2009: 72 (textfig.); Benkendorfer & Soares-Gomes, 2009: 151.

Type locality: Valorous Expedition, North Atlantic, 1450 fathoms (ca. 2650 m depth) (Jeffreys 1876).

Distribution: Morocco, Cape Verde, off USA to Brazil, ca. 80–3700 m depth (Jeffreys 1885; Rosenberg et al. 2009). In Brazilian waters: off Pernambuco state, ca. 640–1235 m depth (Watson 1879); off Cabo de Santa Marta, Santa Catarina state, and off Tramandaí, Solidão and Bojuru, Rio Grande do Sul state (Rios 2009).

New occurrence: Southeastern Brazil, from Espírito Santo to Rio de Janeiro, 295–3450 m depth.

Description: Shell small, conical, relatively thick-walled, with stepped spire. Color nacreous glossy white. Protoconch (~1 whorl) prominent, bulbous, microporous. Teleoconch sculpture (except whorl base) consisting of very strong spiral cords (only a single one visible on early whorls), with widely spaced axial threads and very fine spiral threads between spiral cords and suture; spire whorls bearing two visible spiral cords: a weaker subsutural one, and a stronger supramedian that produces a distinct keel; axial threads prosocline above median keel and opisthocline below it, creating a continuous sigmoid pattern. Whorl base sculptured by 6–8 spiral cords; axial threads between cords. Whorls strongly concave between cords and suture, with overall angular shell profile. Suture obscured by subsutural carina. Aperture quadrangular, with a strong columellar tooth and three labral sinuses: a deep subsutural sinus; a shallow sinus in peripheral part of basal region of aperture; and a very shallow sinus in palatal region of aperture, corresponding to the carina. Umbilicus imperforate, resulting in a strengthened and sinuous columellar region.

Measurements (in mm): 6¼–7½ whorls, H = 3.25 ± 0.15; D = 2.7 ± 0.09; h = 1.34 ± 0.44; d = 1.16 ± 0.12.

Material examined: Brazil: Espírito Santo: off São Mateus, continental slope of Abrolhos, 18°55’S 37°49’W, 1200–1500 m, MNHN, 2 shells, (MD55, sta. CP68, 26/v/1987); 18°58’S 37°48’W, 682 m, MNHN, 18 shells, (MD55, sta. SY74, 27/v/1987); 18°59’S 37°47’W, 1540–1550 m, MNHN, ~400 shells, MZSP 116293, ~100 shells (MD55, sta. DC70, 26/v/1987); 18°59’S 37°50’W, 295 m, MNHN, 90 shells, (MD55, sta. DC75, 27/v/1987); 18°58’S 37°49’W, 637 m, MNHN, 40 shells, (MD55, sta. CB76, 27/v/1987); 19°00’S 37°48’W, 950–1050 m, MNHN, 113 shells, (MD55, sta. DC72, 27/v/1987); 18°59’S 37°48’W, 607–620 m, MNHN, 8 shells, (MD55, sta. DC73, 27/v/1987); 19°01’S 37°47’W, 1500–1575 m, MNHN, 83 shells, MZSP 116294, 22 shells (MD55, sta. CB79, 28/v/1987); 19°01’S 37°29’W, 3420–3442 m, MNHN, 1 shell, (MD55, sta. CP65, 25/v/1987); 19°08’S 37°34’W, 3450 m, MNHN, 18 shells (MD55, sta. DS66, 25/v/1987); 19°13’S 37°33’W, 3450 m, MNHN, 8 shells (MD55, sta. SY67, 25/v/1987); E of mouth of Rio Doce, 19°34’S 38°55’W, 340–360 m, MNHN, 86 shells, MZSP 116298, 14 shells (MD55, sta. CB92, 29/v/1987); 19°36’S 38°53’W, 640 m, MNHN, 1 shell (MD55, sta. CB93, 30/ v/1987); continental slope of Abrolhos, 19°40’S 37°48’W, 790–940 m, MNHN, 38 shells, MZSP 116295, 14 shells, (MD55, sta. CB77, 27/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); E of Cabo Frio, 22°50’S 40°15’W, 1835–1872 m, MNHN, 2 shells, (MD55, sta. SY03, 09/v/1987); S of Cabo Frio, 23°41’S 42°06’W, 430–450 m, MNHN, 30 shells, MZSP 116297, 10 shells (MD55, sta. CB104, 01/vi/1987); 23°46’S 42°10’W, 610 m, MNHN, 11 shells, (MD55, sta. CB105, 02/vi/1987); 23°54’S 42°10’W, 830 m, MNHN, 5 shells, (MD55, sta. CB106, 02/vi/1987).

Remarks: The present specimens closely resemble S. formosa, mainly by their teleoconch sculpture and imperforate umbilicus, with a sinuous columellar region of the aperture. Moreover, they compare especially well to S. formosa var. lineata Watson, 1879, but the distinction between subspecies is unclear and this classification is avoided here until these taxa are properly revised. The present records fill the gap in the distribution of this species. Some previous authors (see synonymy above) have usually identified Brazilian specimens of S. formosa as two similar fossil species: S. monocingulata Seguenza (Pliocene, Italy) and S. hapala Woodring (Miocene, Jamaica). Seguenzia formosa could represent a synonym of S. monocingulata, but here we prefer a more conservative classification until a thorough revision of these species is conducted.