Leptochiton samadiae, Sigwart, Julia D. & Sirenko, Boris I., 2012

Sigwart, Julia D. & Sirenko, Boris I., 2012, Deep-sea chitons from sunken wood in the West Pacific (Mollusca: Polyplacophora: Lepidopleurida): taxonomy, distribution, and seven new species, Zootaxa 3195, pp. 1-38 : 18-20

publication ID	https://doi.org/ 10.5281/zenodo.280094
DOI	https://doi.org/10.5281/zenodo.5218596
persistent identifier	https://treatment.plazi.org/id/038787C8-CD18-FFFD-FF70-4B86B161FC17
treatment provided by	Plazi
scientific name	Leptochiton samadiae
status	sp. nov.

Treatment

Leptochiton samadiae View in CoL n. sp.

Figures 4 View FIGURE 4 E, 11, 12

Leptochiton View in CoL n. sp. 4 Sigwart 2008b: 2.32–2.34, figs 2.25–2.29; Sigwart, 2009a: table 2, fig. 2; Sigwart et al. 2011: table 3, fig. 2; Yearsley & Sigwart 2011: table 1.

Type material. Holotype ( MNHN 23697) disarticulated, consisting of mounts of shell, perinotum and radula, 17 paratypes ( MNHN 23698) and 1 paratype ( ZISP).

Type locality. Solomon Islands, 8º39.5´S, 157º23.0´E, 214–243 m; Salomon 2 sta. CP2285.

Etymology. Named after Dr Sarah Samadi of the MNHN, who was critical to the expeditions that procured the material described.

Material examined. 4 specimens in 1 lot from Vanuatu, 8 specimens in 4 lots from the Philippines, 12 specimens in 7 lots from the Solomon Islands.

Distribution. Widely distributed from the Philippines (137–163 m, 989 m), Solomon Islands (197–623 m) and Vanuatu (358 m). Found living and feeding on sunken terrestrial plant remains.

Diagnosis. Animal small up to 7.0 × 4.4 mm. Valves moderately elevated, not beaked. Intermediate valves side margins rounded, anterior margin convex, posterior margin straight, lateral areas not raised. Tail valve with mucro slightly anterior, postmucronal slope straight. Tegmentum with 60 longitudinal rows of raised round granules on central areas; quincunx on lateral areas. Reddish-brown mineral deposit on valves. Aesthete caps strongly projecting. Girdle dorsally densely covered in flattened scales, intersegmental spicules in chitinous cups, ventrally with larger scales. Four gills per side. Radula major lateral teeth with tridentate cusps.

Description. Holotype 7.0 × 4.4 mm. Shell carinated, moderately elevated (elevation ratio 0.32–0.45 in intermediate valves), valves not beaked.

Head valve semicircular, slightly narrower than tail valve. Intermediate valve rectangular, lateral areas not raised, and not depressed near apices, anterior margin slightly convex, and posterior margins nearly straight to slightly concave. Anterior margin of valve II more pronouncedly convex. Sides rounded, apex not projecting.

Tail valve with slightly anterior mucro, anterior margin of jugal area convex, postmucronal slope straight.

Tegmentum sculptured with very small (38 µm), slightly raised, rounded granules arranged in quincunx on lateral and postmucronal areas. Granules on central and pleural areas forming approximately 25–30 distinct longitudinal rows per side (approximately 20 granules per row in central area). Aesthete caps are clearly visible, protruding slightly from aesthete openings. Colour of tegmentum white, older parts of valves (near apex) covered with reddish brown mineral deposit.

Each granule with five aesthetes of approximately equal size. Aesthetes approximately 5.5 µm in diameter.

Articulamentum weakly developed; apophyses small, widely separated, triangular in valves II–VII, more or less trapezoidal in tail valve. Articulamentum forming very small, underfolded ridge along terminal margins of end valves and lateral margins of intermediate valves.

Girdle moderately wide relative to valves, about 0.5 mm wide near valve V in holotype, dorsally densely covered in small, blunt scales (38 × 17 µm) with four or five ribs. Intersegmental areas with larger spicules (up to 250 × 18 µm) embedded in chitinous cups, in the form of Ringschaftnadeln of Thiele (1908). Marginal spicules of two kinds: same as intersegmental large spicules (up to 175 × 16 µm) and ribbed spicules (100 × 13 µm). Ventrally, the girdle is covered with elongate, smooth, flat, pointed scales (55–60 × 12 µm), much larger than the dorsal scales.

Radula of holotype 2.1 mm long, with 32 transverse rows of mature teeth. Major lateral teeth with tridentate heads; denticles of equal width, interior denticle shortest.

There are four gills per side, all will laminae on a single side, except the second gill from the posterior with double laminae.

Gut contents containing cellulose woody material of brown colour.

Remarks. This species superficially resembles L. habei , but differs in the number of aesthetes pores (five in L. samadiae and seven in L. habei ), in their arrangement, and in having a tridentate major lateral cusp (rather than the bidentate major lateral in L. habei ).