Cerithiopsis parviscymnus, 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 : 45-46

Cerithiopsis parviscymnus sp. nov.

urn:lsid:zoobank.org:act:0FE72CD0-C65B-4994-A89E-4A0226556782

( Fig. 23 )

Type material. Holotype: MNRJ 22836 . Paratypes: Brazil: -- Rio de Janeiro state: 23°04ʹS, 40°59ʹW, 17/xii/2004: MNRJ 33017 [2*p]; 22°42ʹS, 40°40ʹW: MNRJ 31370 [1*p]; HAB 16 sta. B5: MNRJ 16565 [1*p].

Type locality. Brazil, off Rio de Janeiro state, Bacia de Santos , SANSED 5 sta.H5(23°28ʹ0.84ʺS, 41°58ʹ12.72ʺW, 147 m) .

Etymology. From the Latin words parvus = little and scymnus = young. This species is named after its short, paucispiral protoconch.

Diagnosis. Protoconch paucispiral with minute granules on first whorl, and small spiral cords on the second one. Early teleoconch whorls with two spiral cords; adapical spiral cord splitting on late teleoconch whorls.

Description. Shell subcylindrical, up to 3.0 mm long, 0.9 mm wide, ratio length/width 3.2–3.5. Protoconch paucispiral, globose, 340–410 μm long, 270–309 μm wide, with 2.5 convex whorls; color light beige, translucent; sparse granules in the first whorl; second whorl with granules near the adapical suture and three or four thin spiral lines on the middle or abapical half of the whorl. Teleoconch with up to eight whorls, rectilinear profile; color light brown, interspaces between nodules on spiral cords slightly darker; two spiral cords (median and abapical) on the initial teleoconch whorls; third cord appearing on the third whorl close to adapical suture and to the median cord, reaching same strength than other cords and becoming well separated from the median one after four whorls; median and adapical spiral cord somewhat closer to each other than median and abapical spiral cord on mature whorls (including body whorl); ~18 nearly orthocline axial ribs on the body whorl; rounded to slightly elliptical, medium-sized nodules (occupying 55–58% of body whorl length); suture shallow; slightly nodulose to nearly smooth subperipheral cord; one slightly nodulose basal cord, and a thin spiral thread may appear below it; aperture rhomboid, small, 0.40–0.50 mm long, 0.30–0.40 mm wide, ratio length/width 1.2–1.3; distinct, open anterior canal; acute posterior sinus; inner lip slightly reflected over the parietal wall.

Remarks. Cerithiopsis parviscymnus shares teleoconch features with other species from Brazil, mainly Cerithiopsis onerata sp. nov. ( Fig. 22 ), such as the later emergence of the adapical spiral cord (apparently from the suture) and ornamentation of the base with one strong basal cord and one thin spiral thread below it. The protoconch mainly distinguishes them, with a paucispiral one in C. parviscymnus (indicative of non-planktotrophic development: Fig. 23G–H ) but multispiral in C. onerata sp. nov. (indicative of planctotrophic development: Fig. 22D–E ). Another species with a paucispiral protoconch from Brazil is Cerithiopsis soubzmaignei comb. nov. ( Cecalupo & Perugia, 2020) ( Fig. 28 ), which has a very different shell shape (pupoid) and teleoconch ornament (e.g., presence of three spiral cords throughout the teleoconch vs. late adapical spiral cord in C. parviscymnus ), in addition to a completely smooth protoconch.

Geographic and bathymetric distribution. Only known from Rio de Janeiro state, at the boundary of the Tropical Southwestern Atlantic Province and the Warm Temperate Southwestern Atlantic Province , from 100 m to 147 m.

Figures

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.

FIGURE 23. Cerithiopsis parviscymnus sp. nov. A: holotype, from Rio de Janeiro state (MNRJ 22836); B–H: paratypes from Rio de Janeiro state (B–C, E–H: MNRJ 33017; D: MNRJ 16565). E: body whorl of shell in C; F: detail of teleoconch whorls of shell in C; G–H: protoconch and detail of embryonic whorl of shell in C. Lengths of whole shells: A: 2.3 mm; B: 3.0 mm; C: 3.0 mm. Scale bars: A–D: 1 mm; E–F: 200 µm; G–H: 100 µm.

FIGURE 28. Belonimorphis cubensis (Rolán & Espinosa, 1992). A–B, D–E: shell from Vitória-Trindade Chain (A–B: IBUFRJ 19448); C: shell from Maranhão state (MZSP 94414); D: protoconch of shell in B; E: detail of teleoconch whorls of shell in B. Lengths of whole shells: A–B: 3.6 mm; C: 4.4 mm. Scale bars: A–C: 1 mm; D–E: 200 µm.