Acanthochitona ciroi Righi, 1971

Jardim, Jaime A., De Almeida, Sergio M. & De Simone, Luiz R. L., 2022, Taxonomic study on the Polyplacophora (Chitonida: Ischnochitonidae et Acanthochitonidae) collected by the Marion Dufresne (MD 55) expedition, with description of a new species, Zoosystema 44 (5), pp. 151-157 : 154-155

Acanthochitona ciroi Righi, 1971

( Fig. 1K-O )

Acanthochitona ciroi Righi 1971: 1350-137 , figs 42-44. — Rios 1994: 19, fig. 26. — Dornellas & Simone 2011: 10, figs 8-9.

MARION DUFRESNE MATERIAL. — Brazil • 3 specimens, 2.2 × 1.1 mm, 2.1 × 1.0 mm, 2.3 × 1.1 mm; Espírito Santo, off Vitória; 20°55’S, 34°01’W; 60 m; continental shelf; MD55 , sta. DC 42, Bouchet, Leal & Métivier leg.; MNHN.

TYPE MATERIAL ( EXAMINED OR NOT). — Holotype. Brazil • 1 specimen, 2.2 × 1.0 mm; Ceará, Off Fortaleza; 04°27’00”S, 37°04’00”W; 58 m; continental shelf; MZSP 25896 .

Paratype. Brazil • 1 specimen, 3.7 × 2.0 mm; Ceará, off Fortaleza ; 02°16’S, 39°44’W; 75 m; continental shelf; MZSP 25897 .

OTHER MATERIAL EXAMINED. — Brazil • 1 specimen, 6.0 × 2.1 mm; Espirito Santo, off São Matheus ; 20°30’20”S, 24°18’43”W; MZSP 134362 .

TYPE LOCALITY. — Brazil; Ceará, Off Fortaleza; 4°27’00”S, 37°04’00”W.

DISTRIBUTION. — Northeastern and southeastern Brazilian coast.

DIAGNOSIS. — Shell covering about 40-45% of dorsal surface area. Valves slightly longer than wide; colour white with some valves orange, showing a white portion with random orange spots. Valve i sculptured by raised ridges on the upper quarter portion and small tegmental pustules on the apex, which increase in dimension toward the margin. Valves ii-vii sculptured as valve i, except for jugal areas, which are sculptured by similar-sized tegmental pustules on the entire surface ( Fig. 1N ). Valve viii elliptic, antemucronal area straight and sculptured as valves ii-vii; mucro median, postmucronal area straight, sculptured as valve i ( Fig. 1O ). Perinotum white with transversal orange stripes, with 16 spicule tufts; margins with hyaline spicules.

REMARK

The MD 55 specimens match the description of Acanthochitona ciroi ( Righi 1971: 135-137, figs 42-44) and are regarded conspecific. The species range is herein extended 2000 kmsouthwards from Ceará to Rio de Janeiro state (off São João da Barra municipality).

Figures

FIG. 1. — A‒E, Stenoplax marcusi (Righi, 1971); A, B, lateral view; C, frontal view; D, dorsal view; E, posterior view; F-J. Acanthochitona terezae Guerra-Junior, 1983; F, G, lateral view; H, frontal view; I, dorsal view; J, posterior view; K‒O, Acanthochitona ciroi Righi, 1971; K, L, lateral view; M, frontal view; N, dorsal view; O, posterior view; P‒T, Acanthochitona oxum n. sp.; P‒Q, lateral view; R, frontal view; S, dorsal view; T, posterior view. Scale bars: 1 mm.