Leptochiton consimilis, 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 : 13-14

publication ID	https://doi.org/ 10.5281/zenodo.280094
DOI	https://doi.org/10.5281/zenodo.5218590
persistent identifier	https://treatment.plazi.org/id/038787C8-CD05-FFE3-FF70-4EA6B11BFD77
treatment provided by	Plazi
scientific name	Leptochiton consimilis
status	sp. nov.

Treatment

Leptochiton consimilis View in CoL n. sp.

Figures 4 View FIGURE 4 A, 5, 6

Leptochiton View in CoL n. sp. 1 Sigwart 2008b: 2.25–2.27, figs 2.11–2.15; Yearsley & Sigwart 2011: table 1.

Type material. Holotype ( MNHN 23691) disarticulated, consisting of mounts of shell, perinotum and radula, 1 paratype ( MNHN 23692).

Type locality. Solomon Islands, 7°43.3´S, 157°39.4´E, 930–977 m; Salomon 2 sta. CP2216.

Etymology. The name of the species is the Latin for "very similar," in reference to its similarity to L. vanbellei .

Material examined. 11 specimens in 4 lots from the Solomon Islands.

Distribution. From the Solomon Islands (912–1218 m). Found living and feeding on sunken terrestrial plant remains.

Diagnosis. Valves highly elevated, not beaked. Intermediate valves side margins rounded, anterior and posterior margins straight, lateral areas slightly depressed at apex. Tail valve mucro central, postmucronal slope straight. Tegmentum with raised oval granules in quincunx, lateral areas not differentiated. Frequently with black mineral deposit all over valve surface. Aesthete caps not projecting. Girdle narrow, dorsally with blunt spicule-scales, intersegmental spines in chitinous cups, ventrally with smooth flat scales. Gills five per side. Radula major lateral teeth with tridentate cusps.

Description. Holotype 11.0 × 5.3 mm. Shell carinated, highly elevated (elevation ratio 0.43 in valve II of holotype), valves not beaked.

Head valve semicircular, very slightly wider than tail valve. Intermediate valves rectangular, lateral areas slightly depressed near apices, anterior and posterior margins nearly straight, except convex anterior margin of valve II. Tail valve with median mucro, anterior margin of jugal area convex, postmucronal slope straight.

Tegmentum uniformly sculpted with raised, rounded granules (65 µm) arranged quincuncially. Colour of tegmentum white, in some specimens (Solomon 2 CP2217, CP2216, CP2253) older parts of the valves (near apex) covered with black or brown deposits.

Each granule with one megalaesthete and four micraesthetes in front, all five aesthete pores of approximately equal size (8 µm diameter).

Articulamentum moderately developed; apophyses small, widely separated, subtriangular in valves II–VII, more or less trapezoidal in tail valve.

Girdle appears narrow, about 0.4 mm wide near valve V, dorsally covered in elongate, bluntly pointed spiculescales (35 µm wide). Intersegmental areas with larger scales, and long needles (190 × 18 µm) embedded in chitinous cups. Marginal spicules 100–150 × 20 µm. Ventrally, the girdle is covered in elongate, smooth, flat, pointed scales (76 × 26 µm), very similar to primary dorsal armature.

Radula of holotype 3.6 mm long, with 36 transverse rows of mature teeth. Major lateral teeth with tridentate heads; the three cusps are of equal width, central denticle the longest, and the interior denticle slightly shorter than the exterior denticle.

Five gills per side, all with laminae on single side, except second gill from the posterior with double laminae.

Gut contents containing cellulose material of light colour.

Remarks. This species superficially strongly resembles Leptochiton vanbellei , and is different primarily in that it L. consimilis has five gills in specimens of all sizes, including juveniles that are the same size as adult L. vanbellei ; whereas L. vanbellei has only four gills per side in specimens of various sizes. Leptochiton consimilis also has four micraesthetes in each aesthete group whereas L. vanbellei has only two micraesthetes per megalaesthete. Although aesthete arrangement can vary over the valve surface, this difference between species could not be accounted for by ontogeny or body size.