Craspedochiton sp.

Dell’Angelo, Bruno, Gori, Sandro, Baschieri, Leonardo & Bonfitto, Antonio, 2010, Chitons (Mollusca, Polyplacophora) from the Maldive islands, Zootaxa 2673 (1), pp. 1-38 : 24-25

Craspedochiton sp.

( Figures 9H–K , 13N )

Material examined: M65: 1 tail valve.

Description: Tail valve oval-shaped, with the anterior margin straight, mucro large and globose, a little elevated, situated anteriorly, anterior slope convex, posterior slope almost straight. Jugal area raised and smooth, with accentuated growth lines and a marked convex jugal sinus. The sculpture consists of closely arranged squarish-oval granules, different sized and more or less radially directed.

Articulamentum white and thick. There are nine slits, which are deep and dorsally slightly elevated, forming a channel. The teeth are broad and roughed dorsally, very irregular. Apophyses rectangular with rounded edges, widely separated by an unconnected sinus.

Remarks: This single tail valve has different characters from those of the preceding species, and we were not able to attribute it with certainty to another of the Craspedochiton species described from the Indian Ocean. The valve resembles C. tesselatus Nierstrasz, 1905 [considered a synonym of C. petasa ( Reeve, 1847) , see Schwabe 2006], but in this species the anterior margin of the tail valve is straight or shallow notched instead of anterior directed as in our valve.

The valve differs from Craspedochiton tetrica (Carpenter in Pilsbry, 1893) by its shape (compared to pl. 4A in Schwabe 2006), the globose and more anteriorly situated mucro (forwardly directed and subcentral in C. tetrica ), the anterior margin straight with a marked convex jugal sinus (convex with a less stressed jugal sinus in C. tetrica ).

A comparison with a photo of the type material of Craspedochiton isipingoensis (Sykes, 1901) put at our disposal by E. Schwabe permit us to confirm the differences with the tail valve of this species, characterized by a central situated mucro and the lacking of the marked convex jugal sinus as in our species.

We therefore identify it as Craspedochiton sp. , waiting for more material to study. The single tail valve found has 9 slits, as reported by E.A. Smith for his “ Craspedochiton laqueatus ”, and it should be possible he had the same species at hand.

Distribution: Craspedochiton sp. is known only from the Maldive Islands.

Figures

FIGURE 9A–G. Craspedochiton cf. laqueatus (Sowerby, 1842), valves, Maldive, MLD02A. A–C, head valve. A, dorsal view. B, detail of the sculpture. C, posterior view. D–G, intermediate valve. D–E, dorsal and frontal views, respectively. F–G, detail of the sculpture of the pleural areas. H–K, Craspedochiton sp., tail valve, Maldive, M65. H, dorsal view. I, detail of the right side. J, detail of the insertion lamina teeth. K, lateral view. Scale bars 1 mm: A, D, E, H, K; 500 µm: C, I, J; 100 µm: B, F, G.

FIGURE 13A–B, Callochiton sp., S. Nilandu Atoll, Maldive, NHM 1903.4.11.71 (living specimen collected by J.S. Gardiner), close-up of the head and tail valves. C–H, Lucilina carnosa (Kaas, 1979), valves, Maldive. C–D, head valves, M13, showing differences in the number of ocelli rows, widths 3 and 3.1 mm, respectively. E, intermediate valve, M13, width 3.5 mm. F, tail valve, M13, width 3.3 mm. G–H, anomalous tail valve, dorsal and posterior views, respectively, M20, width 3.2 mm. I–K, Lucilina sp., valves, Maldive. I, head valve, M13, width 3.1 mm. J, intermediate valve, M20, width 4.7 mm. K, tail valve, M65, width 3.4 mm. L–M, Craspedochiton cf. laqueatus (Sowerby, 1842), head and intermediate valves, Maldive, M65, widths 5.7 and 5.2 mm, respectively. N, Craspedochiton sp., tail valve, Maldive, M65, width 5.8 mm. O–R, Cryptoplax burrowi E.A. Smith, 1884, NHM 1881.11.1.100, syntype, detached valves, coll. Coppinger, Port Molle, Queensland. O–P, intermediate valve, length 4 mm, dorsal and right lateral views, respectively. Q, intermediate valve, length 4.2 mm. R, head valve, length 3.5 mm.