Rimula leptarcis Simone & Cunha, 2014, new species
Creators: name: Simone, Luiz Ricardo L.
name: Cunha, Carlo M.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Lepetellida
Fissurellidae
Rimula
Rimula leptarcis

description: Rimula leptarcis new species
Figures 121–125
Types. Holotype MNHN 25329.
Type locality. Brazil. Espírito Santo; off Itaúnas, continental slope of Abrolhos, 18°56’S 37°52’W, 85–105 m (MD55 sta. DC82; Bouchet, Leal & Métivier col., 28/v/1987).
Diagnosis. Apex slightly curved, located in posterior 1/4 of shell length. Height 44% of length; width ca. 60% of length. Sculpture reticulated, composed by ca. 40 radial cords and concentric cords, both similar sized, forming delicate reticulation. Foramen approximately 23% of shell length; located between anterior and middle thirds of shell.
Description. Shell size 4.4 mm; tall, bluntly conical; height 44% of length. Pure white. Protoconch of one rounded whorl (Fig. 124); situated on right; smooth, glossy; of 210 µm. Foramen cuneiform (pointed anteriorly), width ca. 10% of length; located between anterior and middle thirds of shell length; ca. 10% of shell width, 23% of shell length; edges irregular (Figs 121, 123, 125). Groove anterior to foramen very narrow, flanked by pair of cords similar to neighboring cords. Profile curved ventro-posteriorly; middle third of dorsal surface somewhat straight, parallel to apertural plane; total angle (excluding planar middle region) ca. 80° (Figs 122, 124); beak in posterior ¼ of shell length (in dorsal view), between dorsal and middle thirds in lateral view. Sculpture of ca. 40 narrow radial cords (Figs 121, 122, 124); cords increasing in strength towards aperture; primary, secondary cords intercalating (Figs 122, 124); concentric cords regularly distributed, as wide as radial cords, except close to margin, with radial cords somewhat stronger; radial, concentric sculptures forming delicate reticulation composed of series of rectangular pits (each rectangle about twice as long as tall, longer axis parallel to shell edges); interspaces between cords twice cords’ width; ca. 60 concentric cords along cords close to median line. Selenizone well-marked, edges as tall as radial cords, twice as tall as foramen edges, projected dorsally, with sharp edges; lunules regular distributed (Fig. 125). Aperture planar (Fig. 122), outline elliptical, width ca. 60% of length; edges slightly undulating due to radial cords. Inner surface smooth, glossy (Fig. 123).
Measurements (in mm). Holotype: 4.4 by 1.9.
Distribution. Known only from type locality.
Habitat. Sandy bottoms with coralline red algae, 85–105 m (dead specimen).
Material examined: Type.
Etymology. The specific epithet is a contraction derived from the Greek arkys – arcys, meaning net, and leptos, meaning delicate; a noun in allusion to delicate reticulate sculpture of the shell.
Remarks. Rimula leptarcis differs from R. frenulata Dall, 1889, from the central and northern Caribbean (Farfante 1947: pl. 49), by the more oval basal outline, taller shell, stronger sculpture, and the more central and wider foramen. It differs from R. pycnonema Pilsbry, 1943, by the more elongated shell, and by more abundant and the delicate radial and concentric sculpture. It differs from R. dorriae Farfante, 1947, from Florida, in having much more delicate and denser radial sculpture, by the more demarcated selenizone, and by a more elongated outline. The generic attribution is based on the apex curved downwards, the narrow and elongated foramen, the presence of an anterior foramen furrow, and by the absence of a septum (Pilsbry 1943, Farfante 1947).
description: Published as part of Simone, Luiz Ricardo L. & Cunha, Carlo M., 2014, Taxonomical study on the mollusks collected in Marion-Dufresne (MD 55) and other expeditions to SE Brazil: the Fissurellidae (Mollusca, Vetigastropoda), pp. 437-468 in Zootaxa 3835 (4) on pages 459-460, DOI: 10.11646/zootaxa.3835.4.2, http://zenodo.org/record/249622