Loricella neoguinensis, 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 : 290-293

Loricella neoguinensis n. sp.

( Figs. 1 A, B , 17–19 )

Type material. The holotype (MNHN-IM-2013-45614), BL 16.0 mm, now disarticulated, consisting of mounts of part of the girdle and radula, vial with valves, part of radula and part of girdle and paratype (MNHN-IM-200036178) BL 13.0 mm .

Type locality. Papua New Guinea, 09°12’S, 153°55’E, 306–365 m. ( MADEEP, stn DW 4286, 30.04.2014). Paratype from same station ?

Etymology. Named after the New Guinea Island.

Material examined. Only the holotype and paratype.

Distribution. Only known from the type material.

Diagnosis. Animal of medium size for the genus, oval, moderately elevated, carinated, valves hardly beaked, head valve with 12 elevated, slightly nodulose radial ribs, pits arranged in a random manner on head valve and lateral areas of intermediate valves, tail valve triangular, without caudal notch, and with very short, tucked down postmucronal area, antemucronal area straight. Girdle covered with small, curved, imbricate dorsal scales with mainly granules or rare grooves near edge of distal part. Major lateral teeth of radula with bicuspid dental caps.

Description. Holotype with BL 16.0 mm long. Valves thin, carinated, moderately elevated (dorsal elevation in valve V 0.36), hardly beaked. Lateral areas distinctly raised, side slope slightly convex. Color of tegmentum yellowish with pale brown spots.

Head valve semicircular, much wider than tail valve, anterior margin distinctly lobate, posterior margin widely V-shaped, sculptured with 12 elevated slightly nodulose radial ribs. Intermediate valves broadly rectangular, with front margin concave at both sides of a anteriorly produced (especially in valve II), almost semicircular jugal part, lateral areas slightly raised, separated from central area by nodulose radial rib. Tail valve small, triangular, without caudal notch, and with very short, tucked down postmucronal area, antemucronal area straight, mucro terminal.

Tegmentum of head valve, lateral areas and postmucronal area with numerous small pits arranged in a random manner. Central area of intermediate valves and antemucronal area of tail valve with numerous pits arranged partly in a random manner, partly in short longitudinal rows.

Articulamentum white, apophyses very wide, rather short, connected across the narrow sinus by a short, concave jugal plate notched at the sides. Jugal plates with 5 teeth in valve II, and bilobed in other intermediate valves, insertion plates short, slit formula 10/1 (rare 2)/sinus+2 obsolete, valve IV with two slits in right side, other intermediate valves with one slit per side, slit rays distinctly visible as rows of minute transverse grooves, teeth sharp, strongly pectinated, eaves narrow, finely porous.

Girdle yellowish white with light brown transverse bands, relatively narrow, slightly broadening anteriorly, covered dorsally with small, short, imbricating, bent scales 110–140 x 75–105 μm, ornamented with small granules or sometimes grooves on top. Atiny canal penetrates the body of each scale from top to base. Opposite the sutures and around the head valve are a row of rare (1–2) horny bristles up to 800 µm long, some of which still bear a minute, calcareous, sharp-pointed, terminal spicule, 90–100 μm long. There is a narrow, deep median slit in the girdle, just behind the sinus in the tail valve. Marginal spicules are of two types: long, narrow spicules 100 x 15 μm with feather-like ribs and flattened, sharply pointed spicules 34–51 x 10 μm. Ventrally the girdle is covered with several rows of rectangular scales 60 x 16 μm with three short ribs near the margin and longer rectangular, obtusely pointed scales 104 x 16 μm.

Radula of holotype 4.1 mm long, with 31 transverse rows of mature teeth. Central tooth broad and short with slightly convex blade, major lateral tooth with wide bicuspid head.

Holotype with 24 gills on each side extending from valve II to valve VII, nephridiopore and gonopore arranged between 3–4 and 4–5 gills accordingly counted from the last one.

Remarks. Loricella neoguinensis n. sp. is similar to L. vanbellei in its ribs on the head valve and dorsal scales and marginal spicules, but differs from the latter in having pits arranged in a random manner on the head valve and lateral areas (vs pits arranged in radial rows in L. vanbellei ), insertion plates are strongly pectinated (vs smooth in L. vanbellei ), a sharpened hind margin of the tail valve (vs obtusely angular in L. vanbellei ), a very short postmucronal area, and the ratio of the length of the antemucronal area to the length of the postmucronal area of 6.6 (vs 2.3–3.6 in Loricella vanbellei ). The new species has similar pectinated insertion plates like the shallow water species L. angasi but differs from other deep-sea species of Loricella by having strongly pectinated insertion plates and pits that are arranged in a random manner on the head valve and lateral areas.

Figures

FIGURE 1. Complete specimens of selected species of the genus Loricella. A, B. L. neoguinensis n. sp. Papua New Guinea, holotype (MNHN-IM-2013-45614), BL 16.0 mm; C, D. L. profundior, Tonga Islands, (MNHN-IM-2013-59980), BL 11.5 mm; E-G. L. vanbellei, New Caledonia, (MNHN-IM-2013-69525) BL 16.0 mm; A, C, G. Dorsal view; B, E. Ventral view; D, F. Lateral view. m.f.—mantle fold.

FIGURE 17. Loricella eernissei, New Zealand, (NMNZ M.319766), BL 22.0 mm. A. Dorsal scales, marginal spicules and ventral scales on edge of caudal incision; B. Part of radula; C. Central, first lateral, major lateral and major uncinal teeth of radula; D. Central and first lateral teeth of radula.

FIGURE 18. Loricella neoguinensis n. sp., New Guinea Island, holotype (MNHN-IM-2013-45614) BL 16.0 mm. A. Valve I, dorsal view; B. Valve II, dorsal view; C. Valve V, dorsal view; D. Valve VIII, dorsal view; E. Valve VII, dorsal view; F. Valve VII, tegmentum sculpture in central and lateral areas; G. Valve V, rostral view; H. Valve VIII, lateral view.

FIGURE 19. Loricella neoguinensis n. sp., New Guinea Island, holotype (MNHN-IM-2013-45614) BL 16.0 mm. A. Dorsal scales, marginal spicules and ventral scales; B. Dorsal scales and bristles; C. Dorsal scales; D. Dorsal scales and marginal spicules.