Loricella solomonensis, Sirenko, 2021

Sirenko, Boris, 2021, Composition of the genus Loricella (Mollusca: Polyplacophora: Loricidae) and the description of two new species, Zootaxa 4981 (2), pp. 275-300 : 294-297

Loricella solomonensis n. sp.

( Figs. 20–22 )

Type material. The holotype (MNHN-IM-2009-10555), BL 28.0 mm, strongly damaged, now disarticulated, consisting of mounts of part of the girdle and radula, vial with valves, part of radula and part of girdle .

Type locality. Solomon Islands, 08°32’S, 160°40’E, 420–602 m (SALOMONBOA 3, stn CP2785, 22.09.2007) .

Etymology. Named after the Solomon Islands.

Distribution. Only known from type locality.

Diagnosis. Animal of medium size, maximum length of body c. 28 mm, oval, depressed, carinate, sides weakly convex, valves not beaked, pits arranged in a random manner on the head valve, on lateral areas of intermediate valves and on postmucronal areas of the tail valve, central area of intermediate valves and antemucronal areas with pits arranged more or less in longitudinal rows but in places they are haphazard. Tail valve with small caudal notch. Teeth of insertion plates weakly pectinated. Dorsal scales of girdle with small granules on top. Blade of small central tooth slightly convex. Major lateral teeth of radula with bicuspid dental caps.

Description. Chiton of medium size, body length of holotype 28 mm and width 19 mm, ovoid, depressed (dorsal elevation about 0.25), valves carinate, easily broken. Tegmentum white with thin dirty brown deposits.

Head valve wide, semicircular, without radial ribs. Intermediate valve rectangular, not beaked, anterior margin convex, posterior margin straight, lateral areas slightly raised, separated from central area by a flattened radial rib. Tail valve small, narrower than head valve, antemucronal slope slightly concave, mucro terminal, postmucronal area short (ratio of length of antemucronal area to length of postmucronal area 3.1).

Tegmentum of head valve, lateral areas of intermediate valves and postmucronal area of head valve with numerous small pits arranged in a random manner. Central area of intermediate valves and antemucronal area of tail valve with numerous pits arranged mainly in a longitudinal rows but partly in a random manner. There are several slightly pronounced growth lines in all areas.

Articulamentum white, thin, apophyses very wide, rather short with short jugal plate bilobed in intermediate valves, insertion plates short, slightly pectinated, slit formula c.12/1/sinus+6 obsolete, eaves narrow, finely porous.

Girdle dirty brown because of deposits, narrow, about 2.0 mm in width near valve VI, covered dorsally with small, short, imbricating, bent scales 80–90 x 100–64 μm, ornamented with small granules on top. Atiny canal penetrates the body of each scale from top to base. Opposite the sutures and around the head valve is a row of horny bristles up to 250 µm long, some of which bear a minute, calcareous, sharp-pointed, terminal spicule, 50 x 14 μm. Marginal spicules 72 x 16 μm slightly curved, sharply pointed and with three indistinct riblets on upper half. Ventrally, the girdle is covered with several rows of rectangular, obtusely pointed scales (60 x 31 μm) near the margin and longer rectangular, obtusely pointed scales (100 x 17 μm) in the middle of hyponotum.

Central tooth of radula short with a narrow, convex blade. First lateral tooth slender, the base excavated, distally abruptly broadening to knobby outgrowths on both sides, major lateral tooth with wide bicuspid head.

The holotype has 20 gills on each side extending from valve III to valve VII, nephridiopore and gonopore arranged between 4–5 and 5–6 gills accordingly counted from the last one.

Remarks. Loricella solomonensis n. sp. differs from other members of the genus by having granules on the dorsal scales, and the pits on the tegmentum of the head valve and lateral areas of intermediate valves arranged in a random manner (vs pits arranged in radial rows in all other species except for L. neoguinensis n. sp.). L. solomonensis n. sp. differs from L. neoguinensis n. sp. by the absence of radial ribs on the head valve (vs radial ribs on the head valve in L. neoguinensis n. sp.), a longer postmucronal area (vs very short postmucronal area in L. neoguinensis n. sp.) and a small caudal notch (vs caudal notch is absent in L. neoguinensis n. sp.). The new species differs from L. scissurata by having the characters mentioned above and by having small caudal notch (vs wide caudal notch in L. scissurata ) and longer antemucronal area of the tail valve.

Figures

FIGURE 20. Loricella neoguinensis n. sp., New Guinea Island, holotype (MNHN-IM-2013-45614) BL 16.0 mm. A. Part of radula; B. Insertion plate, ventral view; C. Central and first lateral teeth of radula; D. Insertion plate, lateral view.

FIGURE 21. Loricella solomonensis n. sp., Solomon Islands, holotype (MNHN-IM-2009-10555), BL 28.0 mm. A. Damaged Valve I, dorsal view; B. Valve VII, dorsal view; C. Damaged Valve VIII, dorsal view; D. Valve IV, ventral view; E. Valve VII, tegmentum sculpture in central area; F. Valve VII, rostral view; G. Valve VIII, lateral view.

FIGURE 22. Loricella solomonensis n. sp., Solomon Islands, holotype (MNHN-IM-2009-10555), BL 28.0 mm. A. Dorsal, marginal and ventral scales; B. Dorsal scales and bristles; C. Dorsal scales; D. Dorsal scales and marginal spicules.