Cerithiopsis onerata, Pimenta & Faria & Figueira & Fernandes, 2024

Pimenta, Alexandre Dias, Faria, Raquel Garofalo De Souza, Figueira, Raquel Medeiros Andrade & Fernandes, Maurício Romulo, 2024, Unraveling another of the ‘ Big Fiveʹ: new species and records of Cerithiopsidae from Brazil (Caenogastropoda: Triphoroidea), Zootaxa 5494 (1), pp. 1-71 : 43-44

Cerithiopsis onerata sp. nov.

urn:lsid:zoobank.org:act:AAE29DBE-7CBE-4B48-99D6-89F13A4B1487

( Fig. 22 )

Type material. Holotype MNRJ 36958 . Paratypes: Brazil: -- Espírito Santo state: REVIZEE– Central sta. C1– VV18; IBUFRJ 19639 [1]; -- Rio de Janeiro state: 23°04ʹS, 40°59ʹW, 100 m, 17/xii/2004: MNRJ 33018 [6*p].

Type locality. Brazil, off Rio de Janeiro state: 23°31ʹ59.8S, 41°02ʹ15ʺW, 120 m

Additional material. Brazil: -- Rio de Janeiro state: Campos Basin (23°13ʹS, 41°02ʹW, 93 m), x/2008: MNRJ 31363 [2*].

Etymology. From the Latin word oneratus = filled, loaded. This species is named after the abundance of sculpture in its protoconch.

Diagnosis. First whorl of protoconch with minute granules, followed by short, and irregularly spaced spiral vesicles; subsequent whorls with the adapical half smooth or with minute granules, and the abapical half with prosocline axial ribs crossed by microscopic oblique wrinkles. Teleoconch with the two adapical spiral cords close to each other in the initial whorls, becoming separated in body whorls.

Description. Shell elongated, nearly turriform, up to 3.8 mm long, 1.0 mm wide, ratio length/width 3.3–3.4. Protoconch subcylindrical, beige, 380–465 µm long, 230–285 µm wide, four convex whorls; embryonic shell dome-shaped, with irregular or vesicular (in a spiral orientation) granules; larval shell with ~24 prosocline axial ribs, starting at or slightly above abapical suture ~64% (first whorl of larval shell) or ~45% (second whorl of larval shell) of whorl length, with a mainly smooth zone (except by minute granules below suture) in the adapical part of the whorl; axial ribs more pronounced in the median portion of whorl (resulting in a shouldered profile), where oblique wrinkles are present between ribs. Teleoconch with up to ten whorls, brownish; with three spiral cords, the adapical cord is very thin, almost indistinct, and much close to the median cord in the initial three-four whorls, slowly increasing in size, reaching same size than other cords and becoming fully separated than median cord after five-six whorls (at the body whorl, the adapical cord can be slightly more pronounced than others); ~18 nearly orthocline to slightly opisthocline axial ribs in the body whorl; rounded, moderately large-sized nodules (occupying 61–65% of body whorl length) at intesction s of spiral cords and axial ribs; suture well-defined, with a thin sutural cord; smooth subperipheral cord; one smooth, thick basal cord, 4.5x wider than the thin spiral thread below it; ovate aperture, 0.45–0.58 mm long, 0.33–0.46 mm wide, ratio length/width 1.1–1.5; well-developed, open anterior canal; wide posterior sinus; inner lip slightly reflected over the parietal wall.

Remarks. Cerithiopsis onerata sp. nov. presents a strongly sculptured protoconch ( Fig. 22D–G ), somewhat similar to that of C. balaustium , especially with the distinct, incomplete prosocline axial ribs on the larval shell. However, there are distinct differences in their teleoconch sculpture, shell size and shape. The shell of Cerithiopsis onerata is longer, nearly oblong to turriform, and may reach 3.8 mm length and has up to ten teleoconch whorls ( Fig. 22A–C ) vs. up to 2.0 mm length and five teleoconch whorls in the pupoid shell of C. balaustium ( Figueira & Pimenta 2008) . Another difference consists in the emergence of the adapical spiral cord of the teleoconch: in C. onerata , the adapical cord seems to emerge from the suture above ( Fig. 22B–C ), whereas in C. balaustium the adapical and median cords are fused in initial whorls ( Fig. 20J ).

Geographic and bathymetric distribution. Only known from Espírito Santo and Rio de Janeiro states, in the Tropical Southwestern Atlantic Province . From 51 m to 120 m.

Figures

FIGURE 20A–D. Cerithiopsis aimen Rolán & Espinosa, 1996. Shell from Rio de Janeiro state (MNRJ 16531). FIGURE 20E–H. Cerithiopsis prieguei Rolán & Espinosa, 1996. Shell from Rio de Janeiro state (MNRJ 32617). FIGURE 20I–L. Cerithiopsis balaustium Figueira & Pimenta, 2008. Shell from Rio de Janeiro state (MNRJ 16527). C, G, K: protoconch of shells in B, F and J, respectively; D: detail of teleoconch whorls of shell in B; H, L: detail of protoconch sculpture of protoconchs in G and K, respectively. Lengths of whole shells: A–B: 1.8 mm; E–F: 2.4 mm; I: 1.8 mm; J: 1.7 mm. Scale bars: A–B, E–F, I–J: 1 mm; C–D, G–H, K–L: 100 µm.

FIGURE 22. Cerithiopsis onerata sp. nov. A–B: holotype, from Rio de Janeiro (MNRJ 36958); C–I: paratypes from Rio de Janeiro state (C–D, F–G, H–I: MNRJ 33018; E: IBUFRJ 19639); F: detail of teleoconch sculpture of paratype in D; G–H: protoconchs of paratypes in D and E, respectively; I–J: details of protoconch sculpture of protoconch in G. Lengths of whole shells: A–B: 3.8 mm; C–D: 3.4 mm; E: 3.0 mm. Scale bars: A–E: 1 mm; F: 200 µm; G–H: 100 µm; I–J: 50 µm.