Acanthochitona crinita (Pennant, 1777)

Figs 6G–L, 9O

Chiton crinitus: Pennant 1777: 71, pl. 36, figs 1, A1.

Neotype designated and figured by Kaas (1985: 591, fig. 27), RSMNH 1978.052.02601 (not seen). Type locality: Hebrides Islands, Monach Island, North Uist, U.K. (57°31.5'N: 07°38.5'W).

Acanthochitona crinita: Kaas 1985: 588, figs 7–50 (chresonymy and synonymy); Dell’Angelo & Smriglio 1999: 198, pls 66–68, figs 124–130; Bonfitto et al. 2011: 173, figs 2, 4B, 6B.

Material examined: ST03: 103 valves, 12 head (maximum width 3 mm), 82 intermediate (maximum width 5 mm), and 9 tail (maximum width 3.5 mm) (BD 113 A); ST06: 3 specimens, maximum length 6.5 mm (Fig. 9O), and 11 valves, 10 intermediate (maximum width 2.5 mm), and 1 tail (width 1.8 mm) (BD 113 B); ST11: 9 intermediate valves, maximum width 2.5 mm (ER); PR07: 1 intermediate valve, width 1.7 mm (BD 113 C).

Distribution: Mediterranean Sea, the Atlantic coast of Europe (as far north as Norway), and the northern West African coast, plus São Tomé and Príncipe Islands.

Comparison and remarks: Acanthochitona crinita appears to be very variable, in its tegmental sculpture, dorsal elevation, the shape of the valves, and in the colour of the tegmentum (Leloup 1968 b; Kaas 1985; Dell’Angelo & Smriglio 1999). Also, the shape of the granules is variable, being round to slightly oval, to a more or less elongate drop (Kaas 1985; Bonfitto et al. 2011), but they are always widely separated, not as densely orientated as in A. fascicularis . The granules have a flat or slightly concave surface, with a central macroaesthete and 8–16 microaesthetes irregularly arranged around it.

Kaas (1985) examined the type material of the five northwest African species of Acanthochitona described by de Rochebrune, (1881–1884) (formerly studied by Thiele 1909), i.e. A. dakariensis, A. adansoni, A. bouvieri, A. joallesi, and A. stercorarius . All of these were synonymized with A. crinita by Leloup (1968 b: 68). Kaas concluded that only A. joallesi is a valid species, whereas A. adansoni and A. bouvieri are synonymous with A. crinita (Pennant, 1777) . A. dakariensis and A. stercorarius are considered nomina dubia. Leloup’s (1941) Acanthochitona subrubicunda from Cape Verde Islands may be separated by its broad, wedge-shaped jugal area.