Sagenotriphora sp. 1

Figs 15, 24D, 63

Material examined

BRAZIL – Amapá • 12 specs; 03º58′43″ N, 49º33′24″ W; 2001; MNRJ 32560 * • 3 specs; 03º58′43″ N, 49º33′24″ W; 2001; MNRJ 32561 * • 18 specs; 03º58′43″ N, 49º33′24″ W; 2001; MNRJ 32562 * • 7 specs; 03º58′43″ N, 49º33′24″ W; 2001; MNRJ 32579 * • 1 spec.; GEOMAR II st. 124; MNRJ 33792 * • 3 specs; 02º21′12″ N, 48º29′54″ W; depth 72 m; Mar. 1997; MNRJ 34457 *.

Description

Shell sinistral, elongated, cyrtoconoid, slightly convex profile in adult shells, up to 5.4 mm long, 1.6 mm wide, length/width ratio 2.9 to 3.1. Protoconch multispiral, conical, 4–4.5 convex whorls, 0.40–0.46 mm long, 0.36–0.40 mm wide; embryonic shell dome-shaped, covered by irregular-shaped granules, vesicular/axially-disposed granules appearing in the final and abapical portion of embryonic shell, resulting in axial ribs of larval shell; larval shell with two spiral cords, situated at ~27%–29% and ~60%–61% of last whorl height; ~32 nearly rectilinear to slightly sigmoid axial ribs. Teleoconch with up to ten whorls; two spiral cords (adapical and abapical) at beginning, abapical one continuous to that of protoconch; median spiral cord emerges in fourth or fifth whorl, reaching same size of other cords after 1.5–2.5 whorls; on body whorl, the spiral cords are 0.8–1.3 × as wide as the distance between them; 19– 20 nearly orthocline to slightly opisthocline axial ribs; rounded to slightly elliptical nodules, medium to moderately small size; distinct, well-developed suture, with small sutural cord; wavy subperipheral cord, usually not developing nodules, two thick and slightly wavy to smooth basal cords; three strong supranumerical cords, one between median and abapical spiral cords, other between abapical and subperipheral cords, another between subperipheral and adapical basal cords; ovate to elliptical aperture, with slightly projected outer lip, 0.50–0.61 mm long, 0.33–0.48 mm wide, length/width ratio 1.3–1.5; anterior canal short, curved backwards/downwards, partly or almost closed, 0.16–0.23 mm long, 0.14– 0.17 mm wide, length/width ratio 1.0–1.6; posterior canal is deep sinus, almost detached from aperture, 0.08–0.12 mm long. Light brown to cream-white protoconch, dirty-white to cream-white teleoconch.

Remarks

Sagenotriphora sp. 1, sampled near the mouth of the Amazon River, is similar in several shell features to S. candidula from Florida (USA). The most distinct aspect is the variable shell color of Sagenotriphora sp. 1. It varies from a light brown protoconch and white teleoconch, similar but not equal to typical S. candidula (Fig. 14, usually much clearer than Brazilian shells), to a whitened protoconch or even an almost cream teleoconch in other shells (Fig. 15 A–D), which is somewhat similar to the common western Atlantic species S. osclausum . The white appearance of S. candidula is much more common than the gold appearance of S. osclausum in the examined material of Sagenotriphora sp. 1. It is plausible that Sagenotriphora sp. 1 is a third species of this genus in the western Atlantic, considering the impact of the Amazon River in this region (see Discussion). Once again, the study of soft parts is crucial, as S. osclausum and S. candidula were mainly distinguished by radular morphology, in addition to differences in shell color (Rolán & Fernández-Garcés 2008). Nevertheless, a few shells of S. osclausum are also found among the paratypes of S. candidula (Fig. 14G).

Geographical records

Brazil: Amapá.

Bathymetric distribution

Depth: 72– 103 m.