Phaenomenella samadiae Kantor & Kosyan & Sorokin 2020, n. sp.

Phaenomenella samadiae n. sp.

(Figs 4; 5A, B; 6)

urn:lsid:zoobank.org:act: E2A6F480-9882-4221-BA7D-84760D903882

MATERIAL EXAMINED. — Holotype. South China Sea • MNHN- IM-2013-61617 (sequenced, Figs 4 A-C; 5A; 6A, B, E-G); S.W. off Dong Sha, ZHONGSHA 2015; st. CP4133; 19°59’N, 116°24’E; 999-1070 m.

OTHER SEQUENCED MATERIAL. — South China Sea • 1 lv; MNHN- IM-2013-61674 (Figs 4E, F; 5B; 6C, D); S.W. off Dong Sha, ZHONGSHA 2015; st. CP4134; 19°50’N, 116°27’E; 1128-1278 m. OTHER STUDIED MATERIAL. — South China Sea • 1 lv; MNHN- IM-2013-61670; S.W. off Dong Sha, ZHONGSHA 2015; st. CP4134; 19°50’N, 116°27’E; 1128-1278 m • 2 lv; MNHN-IM- 2013-59393 (Fig. 4D), MNHN-IM- 2013-59665 (Fig. 4G); ZHONGSHA; st. CP4157; 19°48’N, 116°29’E; 1205-1389 m.

ETYMOLOGY. — Named in honour of Sarah Samadi, professor at MNHN, for her leadership in the France-Taiwan research programme in the context of which research cruises in the South China Sea discovered the present new species.

DIAGNOSIS. — Shell large for genus, up to 58.2 mm, broad fusiform with truncated base, short and strongly left reclined siphon canal. Spiral sculpture of distinct cords, more than 20 on last whorl. Radula

with tricuspate central teeth with short rectangular basal part and tricuspate lateral teeth with longest outermost cusp.

DISTRIBUTION. — Presently the species was recorded only in the South China Sea at 1205-1389 m.

DESCRIPTION (HOLOTYPE)

Shell

Shell broad fusiform with truncated base (Fig. 4 A-C), strong, white under periostracum. Spire high, siphonal canal very short, strongly reclined to left. Protoconch and upper teleoconch whorls eroded, remaining teleoconch whorls 6½ in number. Teleoconch whorls convex, last and penultimate whorls less convex than upper ones. Suture distinct, adpressed. Spiral sculpture of distinct rounded on top spiral cords, on first not eroded teleoconch whorl (3 rd remaining) 9 cords, on penultimate 11, on last whorl 24 cords, of which 4 on canal. Cords differing twice in width, the broader ones indistinctly subdivided by shallow spiral groove and with indistinct spiral striation, not visible on most narrow cords. Interspaces between cords from ¼ to more than cord’s width. On shell base and canal cords more broadly spaced. Upper teleoconch whorls with axial ribs, disappearing on last and penultimate whorls. Ribs nearly orthocline, broadly spaced, 12 on first preserved whorl, 14 on antepenultimate.

Aperture broad ovate, white inside, angulated posteriorly, outer lip thick, slightly reflected.Parietal wall and columella with narrow but thick glossy callus with yellowish band along edge.

Shell covered with light olive adhering periostracum, forming densely spaced low axial lamellae, obsolete on cords, but visible in interspaces.

Operculum spanning most of aperture, with distinctly turned leftwards terminal nucleus and weakly angulate in upper part.

Radula (Fig. 5A, B)

Examined in holotype and sequenced specimen MNHN- IM-2013-61674. Very similar in both specimens; central tooth with rather short rectangular basal part with weakly arcuate anterior margin and three short triangular broad cusps. Lateral teeth tricuspate with weakly curved basal side, attached to membrane. Outermost cusp recurved, medium long, inner cup weakly recurved, about 2/3 of outer cusp length. Intermediate cusp shortest, situated slightly closer to inner cusp.

Measurements

Holotype (largest studied specimen), shell length 58.2 mm, last whorl length 35.8 mm, aperture length (without canal) 23.2 mm, diameter 26.7 mm.

Anatomy

Two specimens studied — MNHN-IM-2013-61674, male, sequenced paratype; MNHN-IM-2013-61617, female, holotype. Soft body partly extracted from the shell. Head rather large, with two thick long tentacles. Eye lobes poorly defined, not pigmented in both examined specimens, eyes obviously absent. Mantle of female (Fig. 6B) approximately square in shape, with long siphon. Ctenidium comprises ¾ of mantle length and in average 1⁄5 of mantle width; bipectinate symmetric osphradium slightly narrower than ctenidium and ¾ of its length. Capsule gland medium large, covered by thick rectum and terminated by large vagina. In male’s mantle, prostate gland well-developed, situated parallel and equal in size to rectum. Penis (Fig. 6 C) flattened, terminating in seminal papilla shifted to left side and not surrounded by a circlular fold.

Digestive system. Proboscis almost completely inverted into rhynchodaeum (Fig. 6E, pr). Several bands of proboscis retractors attached at middle part of both sides of rhynchodaeum (Fig. 6E, prr). Anterior oesophagus straight, along ventral side of rhynchodaeum (Fig. 6E, aoe). Valve of Leiblein medium large, situated immediately before nerve ring (Fig. 6G, vl). Salivary glands large (about half proboscis length), fused ventrally (Fig. 6E, F, sg), with thin salivary ducts following along anterior oesophagus. Gland of Leiblein large, S-twisted, situated beneath salivary glands (Fig. 6E, gl) and following along posterior oesophagus and anterior aorta. Stomach small, occupying about 0.25 whorl (Fig. 6D). Posterior mixing area small, posterior oesophagus and intestine wide.

REMARKS

The new species demonstrates some variability in shell shape with more inflated shell outline in smaller specimens.

The new species is most similar in the shell shape to P. mokenorum Fraussen, 2008 from the Andaman Sea, differing in better pronounced spiral cords. Another somewhat similar species is P. insulapratasensis (Okutani & Lan, 1994), which possesses smaller, more ovoid shell with faster incrementing teleoconch whorls and a longer and more distinct canal.