Parachiton hylkiae mauricejayi Schwabe, 2002

Dell’Angelo, Bruno, Gori, Sandro, Baschieri, Leonardo & Bonfitto, Antonio, 2010, Chitons (Mollusca, Polyplacophora) from the Maldive islands, Zootaxa 2673 (1), pp. 1-38 : 5-6

Parachiton hylkiae mauricejayi Schwabe, 2002

( Figures 1A–J , 12A )

Parachiton hylkiae mauricejayi Schwabe 2002: 220 , figs 1–12, text fig. B.

Type: Holotype ZSM 200113697 (9.3 x 4.5 mm) . Paratypes in several Institutions and collections.

Type locality: Réunion, St. Gilles les Bains , lagoon of Grand-Ford .

Material examined: M13: 2 intermediate valves; M17: 1 intermediate valve; M20: 3 valves (1 head and 2 intermediate); M26: 1 intermediate valve; M65: 4 valves (3 intermediate and 1 tail); MLD02A: 1 spm (partially disarticulated and without soft parts) and 5 valves (2 head, 2 intermediate and 1 tail); MLD03A: 1 intermediate valve; MLD04B: 1 head valve; LB03B: 1 spm (length 12.8 mm, Fig. 12A ).

Remarks: A detailed description of this species is given by Schwabe (2002).

Parachiton hylkiae ( Strack, 1993) is different from the other Indian Ocean species of Parachiton : Parachiton eugenei ( Kaas & Van Belle, 1985) from Madagascar and P. ronaldi ( Kaas & Van Belle, 1985) from the Andaman Islands have the granules of the head valve, lateral areas and postmucronal area arranged in quincunx. P. indecorus ( Kaas & Van Belle, 1990) from Natal, South Africa has the granules of the head valve closely radially grooved and lateral and postmucronal areas arranged in quincunx. P. jordanensis ( Anseeuw & Terryn, 2004) from the northern Red Sea differs in the number of radiating granular rows, fewer than in P. hylkiae (see table 2 in Anseeuw & Terryn, 2004), which almost always coalesce creating a chained appearance in P. hylkiae , whereas in P. jordanensis this feature is rarely seen. The main distinguishing characters of these species are reported in Anseeuw & Terryn (2004: table 2). Parachiton sp. (Dell’Angelo et al., 2004) has smooth lateral areas of the intermediate valves.

Schwabe (2002) described a new subspecies of Parachiton hylkiae , P. hylkiae mauricejayi , from the Réunion and Seychelles Islands. This subspecies differs from the nominal species in having a more rounded shape of the tail valve, a less posteriorly situated mucro, a more curved postmucronal slope (directly behind the mucro), and a different arrangement of aesthetes. The aesthetes are triangularly arranged in P. hylkiae , with the megalaesthete situated posteriorly and the two micraesthetes anteriorly (a total of three, Schwabe 2002: fig. C). In P. hylkiae mauricejayi the aesthetes form a square with three aesthetes posteriorly (megalaesthete central) and two micraesthetes anteriorly (a total of five, Schwabe 2002: fig. B).

In our material the arrangement of aesthetes is not as uniform as reported by Schwabe (2002): Fig. 1I shows the granules in the longitudinal chains of an intermediate valve with three (aligned and not triangularly arranged) to five aesthetes (as in P. hylkiae mauricejayi ); in Fig. 1F, a different intermediate valve shows six to seven aesthetes, three almost aligned posteriorly, two anteriorly and one or two more anteriorly. The arrangement of aesthetes is however more similar to the layout described by Schwabe for P. hylkiae mauricejayi , so we attribute our material to this subspecies.

Distribution: Parachiton hylkiae is known from the northern Red Sea, P. hylkiae mauricejayi from Réunion, the Seychelle Islands ( Schwabe 2002) and the Maldive Islands.

Figures

FIGURE 1A–J, Parachiton hylkiae mauricejayi Schwabe, 2002, Maldive. A–B, head valve detached from a living specimen, MLD02A. A, dorsal view. B, detail of the sculpture. C–D, I–J, intermediate valve detached from a living specimen, MLD02A. C, dorsal view. D, frontal view. I, detail of the sculpture of the central area, granules in the longitudinal chains. J, the same, by a lateral view. E–F, intermediate valve, M65. E, dorsal view of the half side. F, detail of the sculpture of the central area. G–H, tail valve, M65. G, lateral view. H, dorsal view. Scale bars 1 mm: C, D, G, H; 500 µm: A, E; 50 µm: B, F, I; 10 µm: J.

FIGURE 12A, Parachiton hylkiae mauricejayi Schwabe, 2002, living specimen, Maldive, LB03B, length 12.8 mm. B, Ischnochiton albinus Thiele, 1911, living specimen, Maldive, M13, length 5.2 mm. C, Ischnochiton feliduensis E.A. Smith, 1903, Maldive, Felidhoo Atoll, Holotype, NHM 1903.9.17.25, length 6 mm. D, Tegulaplax hululensis (E.A. Smith, 1903), living specimen, Maldive, M28, length 10.5 mm. E–F, Callochiton sp., S. Nilandu Atoll, Maldive, NHM 1903.4.11.71 (living specimen collected by J.S. Gardiner), length 6.6 mm. G, Lucilina sp., living specimen, Maldive, M07, length 4 mm. H, Lucilina indica (Leloup, 1981), holotype (MNHN), Madagascar, Tuléar, length 8 mm. I, Acanthopleura miles (Carpenter in Pilsbry, 1893), living specimen, Japan, Okinawa, Sesoko Island, length 29.2 mm. J, Schizochiton incisus (Sowerby, 1841), living specimen, Indonesia: inside lagoon of Woka Island, off South Halmahera, 1°2.02’S, 128°13.97’E (ZSM Mol 20052075), length 40 mm. K, Acanthochitona penicillata (Deshayes, 1863), living specimen, Maldive, MLD04A, length 6.5 mm. L, Craspedochiton cf. laqueatus (Sowerby, 1842), living specimen, Maldive, M59, length 13.5 mm. M–Q, Craspedochiton laqueatus (Sowerby, 1842), NHM type material, Philippines, Mindoro, Calapan. M, lectotype (NHM 1988071/1), length 17.4 mm. N, paralectotype (NHM 1988071/2), length 17.5 mm. O–Q, paralectotypes (NHM 1988071/3-5), length respectively 16, 13.2 and 11.3 mm. R–S, Cryptoplax burrowi (E.A. Smith, 1884), living specimen, Maldive, M07, length ca. 11.7 mm. T, Cryptoplax burrowi (E.A. Smith, 1884), living specimen, Indonesia, ZSM Mol 20033081, length 25.4 mm. U–X, Cryptoplax burrowi (E.A. Smith, 1884), NHM 1992 053, syntypes, H. Cuming colln., Port Adelaide, S. Australia, length respectively 56.4, 38.5, 47 and 45.1 mm.