Seguenzia elegans Jeffreys, 1885

Salvador, Rodrigo B., Cavallari, Daniel C. & Simone, Luiz R. L., 2014, Seguenziidae (Gastropoda: Vetigastropoda) from SE Brazil collected by the Marion Dufresne (MD 55) expedition, Zootaxa 3878 (6), pp. 536-550 : 544-546

Seguenzia elegans Jeffreys, 1885

( Figs. 19–21 )

Seguenzia elegans Jeffreys, 1876: 201 [nomem nudum].

Seguenzia elegans Jeffreys, 1885: 42 (pl. 5, fig. 1–1a); Clarke, 1959: 232; Clarke, 1961: 350 (pl. 2, figs. 5, 7; pl. 3, fig. 5); Abbott, 1974: 38; Gofas et al., 2001: 184, Segers et al., 2009: 5.

Seguenzia cf. elegans: Quinn, 1983b: 728 (figs. 5, 26).

Type locality: Porcupine Expedition, 1870, Atl. St. 16, 17, 17a, off the coast of Portugal, 740–1095 fathoms (ca. 1350–2000 m depth) ( Jeffreys 1885).

Distribution: North Atlantic: Bay of Biscay, off Portugal ( Jeffreys 1885); off Bermuda ( Clarke 1959); off Yucatan, Mexico ( Quinn 1983b). South Atlantic: Cape Basin and Argentine Basin ( Clarke 1961).

New occurrence: Southeastern Brazil, Espírito Santo, from 1540 to 3450 m depths.

Description: Shell small, conical, relatively thin-walled, with stepped spire. Color translucent to nacreous glossy white. Protoconch (~1 whorl) prominent, bulbous, microporous; transition to teleoconch sometimes visible as an orthocline line, but not always well-marked. Teleoconch sculpture (except whorl base) consisting of strong spiral cords, with well-marked axial threads and very fine spiral threads between cord and suture; spire whorls bearing two visible spiral cords: a weaker subsutural one, and a stronger supramedian that produces a distinct keel; a third strong cord (though weaker than the supramedian) can be observed emerging below the abapical suture. Distance between axial riblets roughly equal to three times rib width; axial threads prosocline above median keel and opisthocline below it, creating a continuous sigmoid pattern. Whorl base sculptured by 8–10 spiral cords; axial threads between cords, becoming fainter toward umbilicus. Whorls slightly concave between spiral cords, but with overall rounded profile. Suture obscured by subsutural spiral cord. Aperture rounded quadrangular, with wellmarked callus, 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 umbilical carina. Umbilicus narrow, deep, with well-marked (stronger than adjacent spiral cords) but smooth edge.

Measurements (in mm): 5¾–6¾ whorls, H = 2.7 ± 0.27; D = 2.50 ± 0.18; h = 1.37 ± 0.18; d = 1.02 ± 0.14. Material examined: Brazil: Espírito Santo: off São Mateus, continental slope of Abrolhos, 18°59’S 37°47’W, 1540–1550 m, MNHN, 11 shells, MZSP 116279, 5 shells (MD55, sta. DC70, 26/v/1987); 19°08’S 37°34’W, 3450 m, MNHN, 1 shell (MD55, sta. DS66, 25/v/1987).

Remarks: Specimens of S. elegans can be easily distinguished by their overall roundish profile and numerous and closely-packed spiral cords on the basal portion of the whorls. The species has an amphi-Atlantic distribution, but this is the first record from southern Brazilian waters.

Figures

FIGURES 19 – 24. Seguenzia from the MD 55 expedition. 19 – 21. Seguenzia elegans from Espírito Santo; 19. MNHN (MD 55 sta DC 70), apertural view (H = 2.8 mm); 20. Same, lateral view under SEM; 21. Same, protoconch detail under SEM (scale bar = 0.1 mm); 22 – 24. Seguenzia formosa from Espírito Santo; 22. MNHN (MD 55 sta DC 70), apertural view (H = 3.3 mm); 23. MNHN (MD 55 sta DC 72), slightly lateral view under SEM (H = 3.4 mm); 24. Same, protoconch detail under SEM (scale bar = 0.1 mm).