Craspedochiton foresti (Leloup, 1965)

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 : 188-190

Craspedochiton foresti (Leloup, 1965)

Figs 7A–T , 9P–S

Notoplax foresti Leloup 1965: 155 , text figs 1–3, pls 1–2; Kaas 1979: 873; Kaas 1986: 20 [as synonym of Notoplax (Spongiochiton) productus ]; Kaas 1989: 109 [as synonym of Notoplax (Spongiochiton) producta ]; Kaas & Van Belle 1998: 75 [as synonym of Notoplax (Spongiochiton) producta ].

Holotype, MNHN 5922 (disarticulated). Type locality: Príncipe Island, Caroço Isl. , 2–8 m, “Calypso” st. 88, 26.vi.1956.

Craspedochiton foresti: Strack 1996: 132 (in the discussion of Craspedochiton productus ).

Material examined: ST03: 2 specimens, slightly curled, maximum length 16 mm ( Figs 9P–S ) ( BD 114 A); ST03: 1 specimen, disarticulated and coated for SEM analysis ( MZB 49763 ) ; ST03: 1 tail valve, length 3.5 mm ( BD 114 B); ST04: 1 specimen, length 4.5 mm ( BD 114 C); ST07: 5 specimens, slightly curled, maximum length 29 mm ( BD 114 D); ST07: 1 specimen in alcohol, curled, length 15 mm ( BD 114 E); ST07: 1 specimen in alcohol, strongly curled, length 10 mm (NSMT-Mo 78636); PR04: 5 specimens, slightly curled, maximum length 18 mm ( BD 114 F); PR06: 1 specimen in alcohol, slightly curled, length 16 mm ( ZSM Mol-20040209).

Distribution : São Tomè and Príncipe Islands.

Comparison and remarks: A detailed description of this species is given by Leloup (1965), pertaining to the genus Notoplax H. Adams, 1861 . We confirm the assignment of the species to Craspedochiton , already reported by Strack (1996), based mainly on the wide expansion of the anterior girdle. The status of the relationship between the genera Notoplax and Craspedochiton was discussed by Gowlett-Holmes (1991), who redefined the genus Notoplax , and considered it to be restricted to Australia and New Zealand (but see under Notoplax sp. ).

We give only some information additional to the original description, based on the SEM observations. The tegmentum is covered by well separated pustules of irregular shape, from roundish/oval to squarish/rectangular, some of them coalesced, giving the impression of orientation in a radiating pattern from the jugum in the intermediate valves ( Figs 7D, 7H ) and in the antemucronal area of the tail valve.The pustules are elevated and of cylindrical shape ( Fig. 7H ), with up to 15 or more ( Fig. 7G ) microaesthetes, disposed without any apparent order. The microaesthetes are also present in the interpustular space.

The radula is probably not useful for distinguishing between species of Craspedochiton (H. Saito pers. comm.). The radula of C. foresti ( Fig. 7Q–T ) is similar to that of C. productus illustrated in Saito (2004: figs 5E, F). The radula of C. foresti has minute granulations on the upper surface of the cusps ( Fig. 7S–T ), but it remains unclear whether this character has specific relevance. Some other species in different genera also show such granulation, e.g. Craspedoplax variabilis (H. Adams, 1864) , and Leptoplax curvisetosa (Leloup, 1960) (Saito 2004: figs 4C, 8F).

Craspedochiton . foresti was considered a synonym of C. productus (Carpenter in Pilsbry, 1892) by Kaas (1979: 873), who stated: “I received from the M.N.H.N. the holotype of Notoplax foresti Leloup, 1965 … The specimen originates from Ile Príncipe, Gulf of Biafra. Though it was disarticulated it appears from the shell plates and the preparations of the girdle, that it does not substantially differ from C. productus and must be regarded as another synonym of the latter, which extends the range of distribution considerably”. Subsequent authors (e.g. Kaas 1986, 1989; Kaas & Van Belle 1998) followed this decision.

We re-examined both species and became aware that C. productus can easily be separated from C. foresti , mainly on the basis of the structure of the valves: intermediate and tail valves more oval in C. foresti , but trapezoidal in C. productus ; larger and triangular jugal area in C. productus , narrow and rectangular in C. foresti ; pustules more dense and more irregularly arranged in C. productus ; wider apophyses in C. productus ; slit formula 5 / 1 / 4 in C. productus , 5 / 1 / 7 in C. foresti , with short and irregular slits. The valves of a specimen of C. productus from South Africa (NSMT-Mo 72867) are illustrated for comparison ( Figs 8A–F ). The differences from C. productus have already been discussed by Leloup (1965: 159): “ N. productus se caractérise par des valves intermediaries proportionnellement plus élevées, au sinus plus large, aux lames d’insertion plus obliques et à bords latéraux du tegmentum plus obliques”.

Thiele (1909: 33) described another congener from the Atlantic coast of Africa: Craspedochiton liberiensis Thiele, 1909 . He examined a single specimen, which was 7 mm in length. Comparison with a 4.5 mm long specimen from ST04 indicates that Thiele had another species in hand. C. liberiensis exhibits at this size a more or less regular pattern of nearly round granules, which are elongated in our small specimen. Thiele (1909, pl. 4, fig. 30) illustrated an intermediate valve in which the arrangement of the granules are directed towards the indistinct jugal area. This is contrary to the pattern on our examined juvenile. The specimen’s jugal area is clearly wedge-shaped, well demarcated from the pleural area, and the granules are directed outwards. Whether C. liberiensis is a valid species or, as concluded by Kaas and Van Belle (1998), a synonym of C. productus , needs to be clarified by comparing a number of valves and specimens that are of similar size. Such comparisons are beyond the scope of the present study.

Figures

Fig. 7. (A–T) Craspedochiton foresti (Leloup, 1965), São Tomé Island, ST03, specimen disarticulated and coated for SEM analysis, MZB 49763:(A–C) head valve, (A–B) dorsal and ventral views, (C) detail of the sculpture, (D–H) intermediate valve, (D–F) dorsal, frontal, and ventral views, (G–H) detail of the sculpture in different views, (I–L) tail valve, dorsal, ventral, lateral, and frontal-lateral views, (M–P) girdle formations, (M) dorsal scales, in situ, (N) detail of a dorsal scale, (O) tuft of spines, (P) ventral scales, (Q–T) radula, (Q–R) detail of central and first two lateral teeth, (S) the same, lateral view, (T) detail of the minute granulations present on the upper surface of the cusps. Scale bars = 1 mm (A, B, D, E, F, I, J); 800 μm (K, L); 300 μm (C, G); 200 μm (H); 60 μm (O, Q); 40 μm (R, S); 20 μm (M, P); 8 μm (T); 6 μm (N).

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.

Fig. 8. (A–F) Craspedochiton productus (Carpenter in Pilsbry, 1892) from South Africa (NSMT-Mo 72867), specimen disarticulated:(A–B) head valve,width 11.2 mm, dorsal and ventral views, (C–D) intermediate valve, width 13.1 mm, dorsal and ventral views, (E–F) tail valve, width 9.1 mm, dorsal and ventral views; (G–J) Notoplax sp., São Tomé Island, ST03, intermediate valve: (G–I) dorsal, frontal, and ventral views, (J) detail of the sculpture. Scale bars = 800 μm (G); 600 μm (H); 500 μm (I); 80 μm (J).