Acanthochitona crinita ( Pennant, 1777 )

Dell’Angelo, Bruno, Schwabe, Enrico, Gori, Sandro, Sosso, Maurizio & Bonfitto, Antonio, 2014, Chitons (Mollusca, Polyplacophora) from São Tomé and Príncipe Islands, African Invertebrates 55 (2), pp. 171-200 : 188

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.

Figures

Fig. 6. (A–F) Lepidochitona rolani Kaas & Strack, 1986, São Tomé and Príncipe Islands: (A) complete specimen from ST06, (B–D) PR07, intermediate valve, (B–C) dorsal and frontal views, (D) detail of the sculpture,(E–F) ST11,tail valve,(E)dorsal view,(F) detail of the sculpture;(G–L) Acanthochitona crinita (Pennant, 1777), São Tomé Island, ST03, intermediate valve: (G–I) dorsal, lateral and frontal views, (J) detail of the sculpture, (K–L) detail of granules in different views. Scale bars = 1 mm (A, B, E); 800 μm (G, I); 600 μm (H); 200 μm (F); 100 μm (D, J); 80 μm (L); 60 μm (K).

Fig. 9. (A–B) Stenoplax hernandezi sp. n., São Tomé Island: (A) ST06, Holotype, length 7.6 mm, MZB 49751, (B) ST03, length 8 mm, specimen disarticulated for SEM analysis; (C–E) Callochiton saotomensis sp. n., São Tomé Island: (C) ST03, Holotype, length 4.6 mm, MZB 49761, (D) ST06, length 4.9 mm, Paratype NHMUK, (E) ST06, length 4.4 mm, Paratype ZISP 2198; (F–G) Chiton lyratus Sowerby, 1840, NHMUK 1979176, two Syntypes, type locality: unknown (restricted to Príncipe Island);(H–J) Chiton canariensis d’Orbigny,1839,NHMUK 1854.9.28.152,three Syntypes, type locality: Canary Islands; (K–N) Rhyssoplax canariensis (d’Orbigny, 1839), colour variations, (K) ST03, length 20.5 mm, (L) ST02, length 8 mm, (M) ST03, length 13.2 mm, (N) ST02, length 8.8 mm; (O) Acanthochitona crinita (Pennant, 1777), São Tomé Island, ST06, length 6.5 mm; (P–S) Craspedochiton foresti (Leloup, 1965), São Tomé Island, ST03, (P–Q) length 16 mm, dorsal and ventral views, (R–S) length 10 mm, dorsal and lateral views.