Lepidozona excellens Sirenko, 2016

Sirenko, B. I., 2016, New and rare species of the genus Lepidozona (Mollusca: Polyplacophora) from the South China, East China and the Philippine seas, The Bulletin of the Russian Far East Malacological Society 20, pp. 28-46 : 40-45

Lepidozona excellens Sirenko sp. nov.

Figs. 11–14 , 15F

urn:lsid:zoobank.org:act:1D80ABE6-D251-4097-BF78-C47DE1060102

T y p e. The holotype ( ZISP no. 2295), now disarticulated consisting of mount of part of girdle and radula, vail with valves, part of radula and part of girdle, and 3 paratypes ( ZISP 2296 ) .

T y p e

l o c a l i t y. Philippine Sea, 26 ° 46 ′ N, 135 ° 4 ′ E, depth 380–420 m.

E t y m o l o g y. The name is Latin for splendid sculpture of tegmentum.

M a t e r i a l e x a m i n e d. Philippine Sea, 26 ° 46 ′ N, 135 ° 4 ′ E, depth 380–420 m, R / V Odissey, stn 37, holotype ( ZISP no. 2295), BL 18.0 mm, 3 damaged paratypes ( ZISP no. 2296), BL 18–24 mm, 04.02.1985, leg. M. Kolesnikov.

D i s t r i b u t i o n. Known only from the type locality.

D i a g n o s i s. Animal of moderate size, oval, little raised, carinated, valves not beaked, except valve II. Head valve sculptured with well elevated radiating ribs, each rib composed of round pustules, central areas of intermediate valves with about 20 longitudinal elevated inwardly curving ribs, interstices decidedly latticed, jugal part of valve II with a feather-like figure, formed by forwardly diverging riblets. Postmucronal slope of tail valve convex. Dorsal scales bent, with 9–11 narrow ribs and with a short, striated, nipple-like prolongation near the top. Central tooth of radula narrow, distally widening to a strong convex blade, head of major lateral tooth unidentate.

D e s c r i p t i o n. Holotype of moderate size, BL 18.0 mm, valves low elevated (dorsal elevation 0.27), carinated, not beaked. Color of tegmentum bluish white in central portion of intermediate valves and creamy in other areas and girdle.

Head valve semicircular, slightly wider than tail valve, posterior margin widely V-shaped, notched in the middle, tegmentum sculptured with well elevated radiating ribs, each rib composed of round pustules, Intermediate valves broadly rectangular, front margin concave in the jugal part, and splayed laterally, anterior margin of the jugal part clearly forwardly produced, side margins slightly rounded, posterior margin about stright, central areas sculptured with about 20 longitudinal elevated inwardly curving ribs per side, interstices decidedly latticed, jugal part of valve II with a feather-like figure, formed by forwardly diverging riblets, lateral areas visibly raised, sculptured with 5–6 well elevated diagonal bifurcated ribs ornamented with round, elevated pustules. Tail valve with anterior mucro, antemucronal slope straight, postmucronal slope little concave, antemucronal area sculptured like central area of intermediate valve, postmucronal area sculptured like head valve.

Articulamentum white, with two creamy streaks radiating from the apices, smooth, apophyses wide, semi-oval, connected across the shallow sinus by a short, concave, slightly denticulated jugal plate, weakly notched at the sides, slit formula 10/1/10, slit rays hardly indicated, teeth sharp, eaves very narrow, solid.

Girdle of moderate width, 0.7 mm wide near valve V, (width of the valve 12 mm), dorsally covered with slightly bent, small, obsoletely longitudinally ribbed (10–11 ribs) large scales (270x300), some of them with a striated, nipple-like prolongation near the top. Marginal spicules of several kinds: long smooth needles (400x20 μm), flattened spicules (130x22 μm) with 2–3 longitudinal ribs on dorsal side, flattened spicules grooved in two directions (feather-lile) (122x24 μm), spicules with 4 longitudinal ribs around whole spicule (103x18 μm), short spicules (52x12 μm)with 6 longitudinal ribs around whole spicule, wedge-shaped, obliquely grooved spicules (150x47 μm), and short, triangle scales with one small rib on top. Ventrally girdle covered with long rectangular scales (90x18 μm).

Radula of holotype 7.3 mm long with 28 transverse rows of mature teeth. Central tooth of radula narrow, distally widening to a strong convex blade, head of major lateral tooth unidentate.

Twenty-eight gills per side arranged from valve II to valve VIII.

Gut contained mainly detritus, a few foraminiferans and sand.

R e m a r k s. The new species is similar to Lepidozona clathrata (Reeve, 1847) from the Gulf of California and L. cooperi (Carpenter in Dall, 1879) from the western coast of North America in the sculpture of their tegmentum. The new species differs from both those species in having an anterior mucro of the tail valve (vs. central in L. clathrata and L. cooperi ), the jugal part of valve II with a feather-like figure (vs. with wedge-like figure in L. clathrata and L. cooperi ), and inwardly curving longitudinal ribs in pleural parts of intermediate valves (vs. straight longitudinal ribs in L. clathrata and L. cooperi ). Moreover L. excellens sp. nov. has dorsal scales with longitudinal ribs (vs. practically smooth in L. clathrata ).

Figures

Fig. 11. Lepidozona excellens, holotype, BL 18.0 mm, Philippine Sea, R/V Odissey, stn 37, 380–420 m; A – valve I, dorsal view; B – valve II, dorsal view; C – valve V, dorsal view, D – valve VIII dorsal view; E – valve VIII, lateral view; F – valve VII, detail of tegmentum in jugal, central and lateral areas; G – valve VII, detail of tegmentum in, central and lateral areas; H – valve V, rostral view.

Fig. 12. Lepidozona excellens, holotype, BL 18.0 mm, Philippine Sea, R/V Odissey, stn 37, 380–420 m; A, C – dorsal scales, marginal spicules, scales and ventral scales; B dorsal scales; D – head of major lateral tooth of radula.

Fig. 13. Lepidozona excellens, holotype, BL 18.0 mm, Philippine Sea, R/V Odissey, stn 37, 380–420 m; A, B – radula.

Fig. 14. Lepidozona excellens, holotype, BL 18.0 mm, Philippine Sea, R/V Odissey, stn 37, 380–420 m; A, B – dorsal scales; C–I – marginal needle, scales and spicules; J – ventral scale; K – nipple projection on dorsal scale; L – central and lateral teeth of radula; M – head of major lateral tooth of radula. Scale bar 100 µm.

Fig. 15. Color images of species of genera Lepidozona. A – Lepidozona bisculpta, BL 8 mm, Vietnam, Tonkin Bay, 6–7 m, on old corals; B – Lepidozona bisculpta, with 5 valves, BL 8 mm, Vietnam, Tonkin Bay, 6–7 m, on old corals; C – Lepidozona bisculpta, with 7 valves, BL 8 mm, Vietnam, Tonkin Bay, 6–7 m, on old corals; D – Lepidozona acostata, holotype, BL 8 mm, south Vietnam, R/V Odissey, trawl 59, 310 m, on sunken wood; E – Lepidozona acostata, paratype, BL 8 mm, south Vietnam, R/V Odissey, trawl 59, 310 m, on sunken wood; F – Lepidozona excellens, holotype, BL 18.0 mm, Philippine Sea, R/V Odissey, stn 37, 380–420 m.