Costaclis egregia

Costaclis egregia (Dall, 1889b)

(Figures 3 A–D, 4A–G)

Aclis egregia Dall, 1889b: 325, plate 18, figure 12.

Aclis (Costaclis) egregia Dall, 1889b: Abbott (1974: 132, figure 1456).

Costaclis egregia (Dall, 1889b): Absal„o et al. (2003: 324, figure 1–3); Rios (2009: 194, figure 480 [reproduced from Absal„o et al. 2003]); Absal„o (2010: 92, not figured).

Type material. Lectotype (herein designated): USNM 126791 (Figure 3A). Paralectotype (herein designated): USNM 126799 (Figure 3B), “Blake” stn. 163 (16°03′10″N 61°52′20″W, 1406 m), coll. 20/i/1879, Guadeloupe.

Type locality. Off St. Vincent and the Grenadines, “Blake” stn. 228 (13°11′20″N 61°19′48″W, 1436 m), 19/ ii/1879.

Material examined. Type material; REVIZEE-Central V stn. 4f (14°48′50″S 38°43′58″W, 1700 m), coll. Sup-ply Boat Astro Garoupa, 02/vii/2001: IBUFRJ 12360 † [2 dd]; Oceanprof I stn. 85: IBUFRJ 15247 † [1 dd].

Redescription (Lectotype). Shell whitish, conical, apex small and obtuse, reaching 13.3 mm long, 5.4 mm wide. Larval shell subcylindrical, with about 3.0 convex whorls; smooth; transition to teleoconch unclear. Teleoconch with about 7 whorls, strongly convex; suture deep, well impressed, sloping; false suture not visible; presence of axial ribs, more developed at mid whorls; growth lines visible through all whorls; incremental scars strong, appearing at irregular intervals. Last whorl about 50% of the shell length; base strongly rounded. Aperture broad, pear shaped, acute posteriorly and rounded and slightly advanced anteriorly; outer lip thin, opisthocline, rectilinear, advancing uniformly, maximum projection at distal area; inner lip sinuous, sloping and well demarcated. Umbilical fissure present.

Measurements. Lectotype USNM 126791, ~10 whorls, SL= 13.3 mm; BWL= 6.7 mm; AL= 4.4 mm; SW= 5.4 mm; AW= 3.1 mm. Paralectotype USNM 126799 (protoconch partially broken), ~9 whorls, SL= 11.0 mm; BWL= 5.8 mm; AL= 3.7 mm; SW= 4.6 mm; AW= 2.4 mm. IBUFRJ 15247†, ~11 whorls (protoconch partially broken), SL= 19.8 mm; BWL= 9.4 mm; AL= 5.6 mm; SW= 7.5 mm; AW= 4.2 mm. IBUFRJ 12360, ~8 whorls, SL= 6.9 mm; BWL= 3.9 mm; AL= 2.5 mm; SW= 3.1 mm; AW= 1.6 mm.

Remarks. The shell from USNM 126791 is selected as the lectotype (Figure 3A) since it is the best preserved and the figured specimen by Dall (1889b). A redescription is provided here to be more specific about the features present in the lectotype and to add features not cited in the original description (i.e., protoconch, incremental scars, base, outer lip). Some shells of C. egregia (e.g., paralectotype USNM 126799 [Figure 3B] and IBUFRJ 12360 [Figure 4 A–G]) are covered by a brownish layer of possible minerals, which can be related to the type of environment they inhabit in the deep sea.

Costaclis egregia was formerly introduced in Aclis but later transferred to Costaclis by Bartsch (1947). Bouchet & Warén (1986) did not comment about the status of this species in Costaclis, but their statement that “ … Costaclis was erected by Bartsch for a mixture of slender species with axial ribs, but only the type species can be kept in the genus”, indicates that they disregard this species as a member of Costaclis. However, the presence of numerous and well-developed axial ribs fits the concept of the genus established by Bartsch (1947).

Dall (1889b) described the species without an umbilicus, but an umbilical fissure is usually present in adult specimens (Figure 3C). We can also add to the original description that the protoconch is subcylindrical.

Absal „o et al. (2003) were the first to record C. egregia in Brazil based on material from the continental slope off Northeast Brazil. These authors cited this species in a depth of 250 m, which would be the shallowest record of C. egregia. However, it is an incorrect indication of coordinate and depth. Actually, REVIZEE-Central V stn. 4f corresponds to the coordinate 14°48′50″S 38°43′58″W and depth of 1700 m (Lavrado 2006), which becomes the deepest record of the species. We reassessed the record by Absal„o (2010: annotated list) and this represents the southernmost record of the species (~ 22°S).

Costaclis egregia can be distinguished from C. hyalina, a congener that also occurs in Brazil, by the teleoconch sculpture with more numerous and well-developed axial ribs, and by the more convex teleoconch whorls.

Costaclis egregia can also be distinguished from C. mizon by the less pronounced axial ribs, wider spire angle and by the greater length. One shell of C. egregia studied here (Figure 3C) with 11 whorls reaches 19.8 mm long while the lectotype of C. mizon (Figure 3E) has 15 whorls and is 15.4 mm long.

Geographical distribution. Guadeloupe, St. Vincent and Grenadines (Dall 1889b); Brazil: Bahia, Rio de Janeiro (Absal„o et al. 2003; Absal„o 2010; present study).

Bathymetric distribution. From 1350 m to 1700 m.