Chiton (Chiton) magnificus (Bullock, 1988)

Ibáñez, Christian M, Pardo-Gandarillas, M Cecilia, Méndez, Marco A, Sellanes, Javier, Sigwart, Julia D & Sirenko, Boris, 2021, Phylogenetic position and morphological descriptions of Chiton species from the south-eastern Pacific, Zoological Journal of the Linnean Society 191 (3), pp. 695-719 : 710-712

CHITON (CHITON) MAGNIFICUS DESHAYES, 1827

( FIGS 4E, F , 14–18 )

Chiton magnificus Deshayes, 1827: 454 . Chiton latus: Frembly, 1827 . Chiton magnificus: Pilsbry, 1893: 160 , pl. 30, figs 23, 24. Chiton (Amaurochiton) magnificus magnificus: Bullock, 1988b: 163 , figs 52–54, 57, 58, 64, 65, 68, 72, 73 and 76. Chiton magnificus: Schwabe et al., 2006: 9 , figs 7, 8 and 15. Chiton bowenii: Schwabe et al., 2006 : Sirenko, 2006: 84. Chiton (Chiton) magnificus , Chiton (Chiton) bowenii: Kaas et al., 2006: 111 , 120, fig. 36, 40, map 14 (bibliography and synonymy). Chiton bowenii: Schwabe, 2009: 404–405 .

Type material: MNHN-IM-2000–6039 (syntypes) (not seen). https://science.mnhn.fr/institution/mnhn/ collection/im/item/2000-6039

Type locality: Chile .

Descriptive notes: Size: large, 160 mm long and 81 mm wide on average ( Table 2), although larger individuals have been reported (> 190 mm; Brito, 2017). Colour varies geographically: usually black with light blue dots in the northern part of its range ( Figs 4E , 14A , 15A–C ), blue and blue with orange or red with black in Golfo de Ancud ( Figs 14B–D , 16A–C ) and reddish orange or black in Estrecho de Magallanes ( Figs 4F , 17A–C ). Body shape: elongate oval with low dorsal elevation. Slit formula: 14/1/12–14. Plates: slightly convex head plate with numerous weak radial ribs (about 40 longitudinal ribs per side), with lines on the lateral areas ( Fig. 4E ). Articulamentum: apophyses trapezoidal, insertion plate pectinate ( Fig. 15A, B ). Perinotum: black, moderately broad, dorsally covered with smooth rounded scales of two different sizes ( Fig. 18A, C ), the largest located near the margin and the small scales near the valves. Radula: central tooth rounded. The major lateral is the biggest tooth rounded in shape ( Fig. 18B, D ).

Distribution: Isla San Lorenzo (~ 12°S), Peru to Bahía Tictoc (~ 43°S), Chile ( Bullock, 1988a; Sirenko, 2006; Schwabe, 2009). In this study, we found this species from Huasco (~ 28°S) to Fuerte Bulnes (~ 53.6°S), Chile ( Fig. 1 ).

Remarks: King (1832) described Chiton bowenii from Tierra del Fuego, and Bullock (1988a) provided the new combination as a subspecies C. magnificus bowenii . Schwabe et al. (2006) suggested sufficient morphological differences to separate C. magnificus and C. bowenii . Based on the long-standing doubt about whether C. bowenii represents a taxon at the species-level, and the molecular results indicated no separation based on COI, we consider C. bowenii to be a junior synonym of C. magnificus , representing one particular morphotype among many colour patterns in this variable species (see Discussion).

Figures

Figure 1. Map showing sampling localities. Lines represent the geographical distribution of each Chiton species: 1, Chiton stokesii; 2, Chiton granosus; 3, Chiton cumingsii; 4, Chiton magnificus; 5, Chiton barnesii.

Figure 4. Pictures of Chiton species from the south-eastern Pacific. A, Chiton barnesii live specimen from La Pampilla, Coquimbo, Chile (29°26’11’’S, 71°18’20’’W). B, Chiton stokesii live specimen from Santa Rosa, Ecuador (2°12’39’’S, 80°56’45’’W). C, Chiton cumingsii live specimen from Lagunillas, Coquimbo, Chile (30°06’13’’S, 71°22’59’’W). D, Chiton granosus live specimen from Antofagasta, Chile (23°40’10’’S, 70°24’29’’W). E, Chiton magnificus live specimen from Lagunillas, Coquimbo, Chile (30°06’13’’S, 71°22’59’’W). F, Chiton magnificus live specimen from Puerto del Hambre, Punta Arenas, Chile (53°36’44’’S, 70°55’43’’W).

Figure 14. Images of Chiton magnificus. A, black specimen with light-blue dots from El Soldado, Talcahuano, Chile (36°46’01’’S, 73°10’17’’W). B, blue specimen from Metri, Chile (41°35’58’’S, 72°42’16’’W). C, light-blue specimen with black lines from Metri, Chile. D, red specimen from Metri, Chile.

Figure 15. Chiton magnificus, Chile, La Mission, BL 24.0 mm, 30.12.2004: A, valve I, dorsal view; B, valve V, dorsal view; C, valve VIII, dorsal view; D, valve VIII, lateral view; E, valve VI, detail of tegmentum in central area; F, valve VI, central and lateral areas.

Figure 16. Chiton magnificus, Chile, Huinay, BL 20.0 mm, 05.01.2005: A, valve I, dorsal view; B, valve V, dorsal view; C, valve VIII, dorsal view; D, valve VIII, lateral view; E, valve VI, detail of tegmentum in central area; F, valve VI, central and lateral areas.

Figure 17. Chiton magnificus, Chile, Magellan Strait, Fuerte Bulnes, BL 23.0 mm, 17.05.2000: A, valve I, dorsal view; B, valve V, dorsal view; C, valve VIII, dorsal view; D, valve VIII, lateral view; E, valve VII, detail of tegmentum in central area; F, valve VII, dorsal view.

Figure 18. Chiton magnificus, Chile, Huinay, BL 20.0 mm, 05.01.2005: A, C, dorsal and ventral scales and marginal spicules; B, D, radula.