Tonicia disjuncta, (FREMBLY, 1827)

TONICIA DISJUNCTA ( FREMBLY, 1827) View in CoL

( FIG. 4 View Figure 4 )

Chiton disjunctus Frembly, 1827: 203 View in CoL , suppl. pl. 17, fig. 5.

Tonicia disjuncta View in CoL ; Leloup, 1956: 67, 36– 37 (bibliography). – Dell, 1971: 221. – Leloup, 1973: 19; Leloup, 1980: 7. – Castellanos, 1988: 25, figs 96–98. – Kaas et al., 2006: 295, fig. 119, map 27. – Schwabe et al., 2006: 17, fig. 12 – Kaas et al., 2006: 295, fig. 119, map 27. – Schwabe, 2009: 415.

Tonicia smithi Leloup, 1980: 5 View in CoL , figs 2–5, pl. 1, fig. A. – Sirenko, 2006a: 85, fig. 9. – Schwabe, 2009: 416. – Kaas et al., 2006: 312, fig. 128, map 55.

Type material repository: British Museum of Natural History ( BMNH)

Type locality: Valparaiso, Chile .

Description of T. disjuncta

Body large sized, ≤ 85 mm in length, elongated and oval ( Table 2). Low elevation (dorsal elevation 0.22); valves not beaked. Tegmentum reddish brown, with small blue spots and sometimes with light markings. Head valve semi-circular. Intermediate valves thin, slightly carinated and wide (ratio of width of valve V to its length is 3.2). Anterior margin strongly forwardly angular. Posterior margin concave but for the distinctly protruding apex. Lateral margin rounded. Tail valve about as wide as the head valve. Median mucro subplane. Tegmentum of all valves smooth and glossy; growth lines obsolete. Articulamentum white. Sutural lamina very large and expanded in the forward and sideways directions; connected across the narrow jugal sinus by a long dentate plate. Slit formula 8–9/1/9. Teeth rather long and strongly grooved on the upper side. Girdle very wide, ~1.5 times less than the width of valve V. Colour of the girdle in live animals is similar to the colour of the tegmentum. Dorsal spicules stalked, smooth, curved, generally with sharp points, 100– 120 µm × 15 µm in size. Ventral scales quadrangular, 28 µm × 26 µm. Major lateral tooth of the radula with a bicuspid roundish head. Ctenidia spanning from valve II to valve VIII; 53 per side in a 58 mm specimen.

Remarks

Tonicia disjuncta View in CoL is easily distinguishable from other Tonicia View in CoL by having a uniform reddish-brown colour with blue spots and a girdle that is connected between valves. We conclude that T. smithi Leloup, 1980 View in CoL from Mehuin, Chile, which Kaas et al. (2006) reported as ‘only known from the holotype’ is a synonym of T. disjuncta ( Frembly, 1827) View in CoL .

Distribution: Species are found along the coast of South America from Huasco (northern Chile, ~ 27°S) to the Strait of Magellan (~ 53°S) and near the Falkland Islands (~ 41°S, Atlantic Ocean). This species is found at depths from 0 to 21 m.