Chiton (Chiton), (CHITON)

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 : 700-702

publication ID	https://doi.org/ 10.1093/zoolinnean/zlaa067
persistent identifier	https://treatment.plazi.org/id/039D87D8-FFD1-2925-EF90-3654B69CF9FA
treatment provided by	Felipe
scientific name	Chiton (Chiton)
status

Treatment

CHITON (CHITON) BARNESII GRAY, 1828

( FIGS 4A View Figure 4 , 5 View Figure 5 , 6 View Figure 6 )

Chiton barnesii Gray, 1828: 5 View in CoL ; Reeve 1847: pl. 1, sp. 1. Chiton (Radsia) barnesii: Pilsbry, 1893: 190 View in CoL , pl. 29, figs 10–12; Dall, 1919: 247. Chiton barnesii: Plate, 1899: 59 View in CoL , pl. 4, fig. 191; Leloup, 1956: 46. Chiton barnesi: Otaiza & Santelices, 1985 . Radsia barnesii: Bullock, 1988b: 282 View in CoL , figs 2, 4, 6, 7, 11–13, 15, 31, 32. Chiton (Radsia) barnesii: Kaas et al., 2006: 147 View in CoL , fig. 53, map. 27. Chiton barnesii Schwabe, 2009 View in CoL . Radsia barnesii Araya & Araya 2015: 52 View in CoL , fig. 2.

Type material: NHMUK (holotype) .

Type locality: Coquimbo, Chile .

Descriptive notes: Size: animal reaching a length of 44 mm and width of 27 mm ( Table 2). Colour: creamy white plates with reddish brown stains in the central areas ( Fig. 4A View Figure 4 ), irregular longitudinal bands of reddish brown in lateral triangles. Body shape: wide, oval, low dorsal elevation. Slit formula: 16/1–2/20. Valves fairly flat. Plates: head valve with> 25 ribs with small grains ( Figs 4A View Figure 4 , 5A View Figure 5 ). Intermediate plates usually with two slits. Intermediate plate with numerous aesthetes ( Fig. 5E, F View Figure 5 ). Tail valve back straight to slightly concave ( Fig. 5D View Figure 5 ). Mucro somewhat sharp, the front of the posterior valve is acentric. Articulamentum: broad, moderately and uniformly extended processes, short insertion plates ( Fig. 5B–D View Figure 5 ). Anterior valve with 16 teeth, posterior valve with 16–20 teeth. Perinotum: wide, with overlapping scales; scales rounded triangular in shape and weakly ridged ( Fig. 6A, C View Figure 6 ). Spicules at the girdle margin ( Fig. 6C View Figure 6 ). Radula: central tooth rounded and broad. The major lateral rounded ( Fig. 6B, D View Figure 6 ).

Distribution: We found this species from Antofagasta (~ 23°S), to Los Vilos (~ 32°S), Chile ( Fig. 1 View Figure 1 ). It was previously reported from Coquimbo (~ 29°S) to the Chonos Archipelago (~ 45°S) ( Bullock, 1988a) or from Caldera (~ 27°S) to the Chonos Archipelago (~ 45°S) ( Araya & Araya 2015).

Remarks: Bullock (1988a) placed Chiton barnesii Gray, 1828 in the genus Radsia based on the slitting of the insertion plate. Later, Kaas et al. (2006) removed barnesii to the subgenus Radsia , and recently Araya and Araya (2015) also used the name R. barnesii . Our molecular results suggest that barnesii is nested within the genus Chiton . This species is often confused with C. granosus , but the principal difference is the slit formula: Chiton barnesii (16–17/2–4/19–20), Chiton granosus (12–18/1/14–17).

CHITON (CHITON) STOKESII BRODERIP IN BRODERIP & SOWERBY, 1832

( FIGS 4B View Figure 4 , 5 View Figure 5 , 8 View Figure 8 , 9 View Figure 9 )

Chiton stokesi Broderip in Broderip & Sowerby, 1832: 25. Chiton (Chiton) granosus: Kaas et al., 2006: 122 View in CoL , fig. 41, maps 14–16 (bibliography and synonymy). Type material: NHMUK (syntypes).

Type locality: Port St Elena , Panama .

Descriptive notes: Size: animal reaching 88 mm long, 44 mm wide ( Table 2). Body shape: the angle of the valves is about 110°. Slit formula: 16/1/18. Plates: anterior valve is slightly convex, the postmucronal, posterior valve region is straight ( Figs 4B View Figure 4 , 8A View Figure 8 ). The intermediate valve central region and tail valve antemucronal region, have numerous longitudinal ribs ( Figs 4B View Figure 4 , 8B, F View Figure 8 ). Intermediate plate with numerous aesthetes ( Fig. 8E, F View Figure 8 ). Tail valve back straight ( Fig. 8D View Figure 8 ). Colour: the plates are black, brown, sometimes green ( Figs 4B View Figure 4 , 8A–C View Figure 8 ), with little white stripes in the central area. Articulamentum white, smooth, with narrow jugal separation with inconspicuous jugal lamina between wide apophyses. Perinotum: wide, with overlapping scales; smooth scales rounded triangular ( Fig. 9A, C View Figure 9 ). Spicules at the ventral side of the perinotum ( Fig. 9C View Figure 9 ). Radula: central tooth triangular and hooked. The major lateral triangular ( Fig. 9B, D View Figure 9 ).

Distribution: Guatemala (~ 12°N) to south Ecuador (~ 2°S) ( Bullock, 1988a; Schwabe, 2009). In this study, we found this species from Montañita (~ 2°S), Ecuador to Bonanza (~ 4°S), Peru ( Fig. 1 View Figure 1 ).

Remarks: Chiton stokesii was erroneously included in the new genus Chondroplax by Thiele (1893), but Bullock (1988b) placed it in Chiton s.s.