Tonicia forbesii Carpenter, 1857

Reyes-Gómez, Adriana, Flores-Garza, Rafael, Galeana-Rebolledo, Lizeth, Hernández-Vera, Gerardo, Galván-Villa, Cristian M., Torreblanca-Ramírez, Carmina, Flores-Rodríguez, Pedro, García-Ibañez, Sergio & Ríos-Jara, Eduardo, 2022, Intertidal chitons (Mollusca: Polyplacophora) from the rocky coastline of Guerrero, México, with the description of a new species, Zootaxa 5155 (4), pp. 451-492 : 472

Tonicia forbesii Carpenter, 1857

Figures 2N , 12D–K , 13A–D

Distribution. From Mazatlán, Sinaloa, México to Taboga Island, Panamá Kaas et al. (2006).

Type specimens. According to Kaas et al. (2006) lectotype by designation of Keen (1958), BMNH? but not found.

Type Locality. Narborough Island, Noves Cove , Galápagos Islands .

Material examined. 40 specimens, maximum size of 40.5 mm long 23 mm wide. M (n=5); K (n=3); P (n=6); L (n=4); B (n=6); D (n=2); N (n=8); I (n=1); U (n=5).

Habitat. This species was found in two habitats: in the intertidal on the underside of medium-sized rocks, and in the shallow subtidal (3–6 m) in low wave energy areas on medium-sized rocks buried in sand. The juveniles were mainly collected in the subtidal on smaller rocks and associated with crustose algae. This species was found with C. lurida , I. muscarius and S. limaciformis .

Remarks. Tonicia forbesii was previously studied and reviewed by Thorpe in Keen (1971) and Kaas et al. (2006), who described the morphological characters of the valves and the girdle elements. Our SEM examination included aesthetes and radular teeth features, which revealed a conspicuous aesthete system. In some, the ocelli are scattered in the radial areas of the valves while, in others, they appeared aligned and arranged in groups of 2–4. The radular central teeth showed a small narrow almost imperceptible plate, and the minor lateral tooth is a long plate with a bilobed apex.

Figures

FIGURE 2. Dorsal view of the whole specimens that represent the analyzed species. A, Chaetopleura lurida, BL 27.48 x 15.70 mm, Majahua, Acapulco (CNMO 5229). B, Chaetopleura hanselmani, BL 11.02 x 7.16 mm, Tlacopanocha, Acapulco (CNMO 5804). Ischnochiton muscarius, C, BL 16.62 x 9.77 mm, Angosta, Acapulco (CNMO 5202); D, BL 15.12 x 9.55 mm, Barra de Potosí Protegida, Petatlán (CNMO 5338); E, BL 18.30 x 10.17 mm, Troncones, La Unión (CNMO 5327); F, BL 14.98 x 9.51 mm, La Barrita, Petatlán (CNMO 5315). G, Callistochiton elenensis, BL 12.32 x 7.76 mm, La Barrita, Petatlán (CNMO 5823). H, Callistoplax retusa, BL 20.41 x 9.68 mm, Parque de la Reina, Acapulco (CNMO 5185). Stenoplax limaciformis, I, BL 17.56 x 7.21 mm, Parque de la Reina, Acapulco (CNMO 5179); J, BL 20.12 x 9.15 mm, Tlacopanocha, Acapulco (CNMO 5208); K, BL 17.65 x 8.29 mm, Las Gatas, Zihuatanejo de Azueta (CNMO 5254); L, BL 19.78 x 9.84 mm, Isla Grande, Zihuatanejo de Azueta (UAGRO 0024). Chiton albolineatus, M, BL 23.84 x 14.63 mm, Piedra de Tlacoyunque, Tecpan de Galeana (CNMO 5337). Tonicia forbesii, BL 33.41 x 17.86 mm, Isla Grande, Zihuatanejo de Azueta (CNMO 5255). Acanthochitona arragonites, O, BL 8.80 x 5.2 mm, Las Salinas, Copala (CNMO 5267). Lepidochitona salvadorensis, P, BL 10.63 x 5.7 mm, Barra de Potosi Protegida, Zihuatanejo de Azueta (CNMO 5332).

FIGURE 12. Chiton articulatus, SEM images of a specimen BL 28.3 mm length; A, detail of girdle scales; B, radular teeth; C, detail of central and minor lateral teeth. Tonicia forbesii, BL 19.5 mm, Isla Grande, Zihuatanejo deAzueta (CNMO 5255). Valves in dorsal view, D, head valve; E, intermediate valve IV; F, tail valve. Valves in ventral view, G, head valve; H, intermediate valve IV; I, tail valve; J, detail of lateral and central area of intermediate valve IV; K, detail of lateral area ocelli.

FIGURE 13. Tonicia forbesii, SEM images of a specimen BL 15.2 mm; A, detail of ocelli system in lateral area of intermediate valve IV;B,radularteeth;C, detail of minorandmajor lateral teeth; D, detail ofintermediate valveIV.Acanthochitona arragonites, disarticulated valves of a specimen BL 8.7 mm, Las Salinas, Copala (CNMO 5267). Valves in dorsal view shows the sculpturing details; E, head valve; F, intermediate valve IV; G, tail valve. Valves in ventral view, H, head valve; I, intermediate valve IV; J, tail valve. SEM images of a specimen BL 9.1 mm; valves in dorsal view, K, head valve in dorsal view.