Phaenomenella nicoi, Kantor & Kosyan & Sorokin, 2020

Kantor, Yuri, Kosyan, Alisa & Sorokin, Pavel, 2020, On the taxonomic position of Phaenomenella Fraussen & Hadorn, 2006 (Neogastropoda, Buccinoidea) with description of two new species, Zoosystema 42 (3), pp. 33-55 : 43-48

Phaenomenella nicoi n. sp.

( Figs 5 C-F; 7; 8)

urn:lsid:zoobank.org:act:BC0FCA38-4FC5-40F8-9D8C-159F76CA46BD

MATERIAL EXAMINED. — Holotype. South China Sea • MNHN- IM-2013-61585 (sequenced, Fig. 7 A-C); S.W. off Dong Sha, ZHONGSHA 2015; st. CP4132; 20°07’N, 116°22’E; 958- 988 m.

OTHER SEQUENCED MATERIAL. — South China Sea • 3 lv; MNHN- IM-2013-61637 ( Figs 7H ; 8 E-G), MNHN-IM- 2013-61638 , MNHN-IM- 2013-61639 ( Fig. 7E ); S.W. off Dong Sha, ZHONG- SHA 2015, st. CP4133; 19°59’N, 116°24’E; 999-1070 m • 1 lv.; MNHN-IM- 2013-61673 ( Fig. 7I ); st. CP4134; 19°50’N, 116°27’E; 1128-1278 m • 1 lv; MNHN-IM- 2013-59398 ( Fig. 7D ); st. CP4157; 19°48’N, 116°29’E; 1205-1389 m.

Philippines 6 1 l•; MNHN-IM-2007-34639; AURORA 2007; st. CP2685; 15°00’N, 123°06’E; 1155-1302 m ( Fig. 7 F ) .

OTHER STUDIED MATERIAL. — South China Sea • 2 lv; MNHN- IM-2013-61590 , MNHN-IM-2013-61592 ( Fig. 7K, L ); S.W. off Dong Sha, ZHONGSHA 2015; st. CP4132; 20°07’N, 116°22’E; 958- 988 m • 5 lv; MNHN-IM- 2013-59661 , MNHN-IM- 2013-61636 ( Figs 7J , 8 A-D), MNHN-IM- 2013-63029 , MNHN-IM- 2013-63025 , MNHN-IM- 2013-61638 ; st. CP4133; 19°59’N, 116°24’E; 999- 1070 m • 2 lv, MNHN-IM- 2013-61671 , MNHN-IM- 2013-61672 ; st. CP4134; 19°50’N, 116°27’E; 1128-1278 m • 1 lv; MNHN- IM-2013-59397 ; st. CP4157; 19°48’N, 116°29’E; 1205-1389 m, S off Helen Shoal • 2 lv; MNHN-IM- 2013-61815 , MNHN- IM-2013-59663 ; st. CP4141; 18°49’N, 113°58’E; 1151-1286 m. Philippines • • l•; MNHN-IM-2007-34644 ( Fig. 7 ); AURORA 2007; st. CP2685; 15°00’N, 123°06’E; 1155-1302 m, SL 38.7 mm .

ETYMOLOGY. — Named in honour of Nicolas Puillandre, associate professor of MNHN, our long term co-author and participant of many expeditions with whom we had a pleasure to share the lab bench for long hours.

DIAGNOSIS. — Shell medium sized for genus, up to 42 mm, fusiform with high spire and attenuated, medium long, and slightly inclined to left siphonal canal. Protoconch large, paucispiral, of about 2 whorls. Spiral sculpture of distinct flat on top spiral cords, about 55 on last whorl. Radula with tricuspate central teeth with rectangular basal part and tricuspate lateral teeth with longest outermost cusp.

DISTRIBUTION. — The species is found so far in the South China Sea at 999-1389 m and Philippines (in Philippine Sea) at 1155-1302 m.

DESCRIPTION (HOLOTYPE)

Shell

Shell fusiform with high spire and attenuated siphonal canal ( Fig. 7 A-C), fragile, white under periostracum. Siphonal canal medium long, slightly inclined to left and crossing coiling axis. Protoconch paucispiral, of about 2 whorls, partially eroded as well as upper teleoconch whorls, teleoconch whorls 6 ½ in number. [Better preserved protoconch found in specimen MNHN-IM-2013-61592 ( Fig. 7L ): bulbous, of nearly 2 whorls, diameter 2.05 mm, exposed height 2.1 mm. Protoconch surface eroded, sculpture not seen. Boundary with teleoconch marked by weak (about 5) orthocline ribs.] Teleoconch whorls convex, weakly angulated at shoulder. Suture distinct, shallowly impressed. Spiral sculpture of distinct flat on top spiral cords, covering entire shell surface. Number of cords increasing from 8 on first teleoconch whorl to 19 on penultimate whorl, on last whorl 55 cords, of which about 20 on canal. Cords differing slightly in width, with most narrow on subsutural ramp, interspaces between cords about 1/3-½ of cord’s width. Strong axial ribs present on entire shell, suture to suture on uppermost teleoconch whorls, gradually becoming obsolete on subsutural ramp and absent on ramp of last and penultimate whorls. On last whorl ribs distinct only on shoulder, producing its angulated appearance. Number of ribs stable, i.e., 15-16 per whorl.

Aperture ovate, white inside, angulated posteriorly, outer lip thin, evenly convex, concave at transition to canal. Parietal wall and columella with narrow and thin glossy callus.

Shell covered with very light olive adhering periostracum, forming densely spaced low axial lamellae visible in interspaces between cords.

Operculum partially abraded, when intact ( Fig. 7 D ) spanning most of aperture with distinctly turned leftwards terminal nucleus and rounded upper part.

Radula ( Fig. 5 C-F)

Examined in five specimens, including holotype. Rather similar in all specimens; central tooth with rectangular basal part with weakly arcuate anterior margin and three medium long triangular broad cusps, central one shorter and narrower than lateral ones. Lateral teeth normally tricuspate with weakly curved basal side, attached to membrane. Outermost cusp recurved, medium long, inner cusp weakly recurved, about 2/3 of outer cusp length. Intermediate cusp shortest, situated slightly closer to inner cusp. In one sequenced specimen (MNHN-IM-2013-61673, Fig. 5F ) intermediate cusps of the left lateral teeth of the radula paired, nearly equal in size, while lateral teeth on right side have broader intermediate cusp subdivided on top.

Measurements (holotype)

Shell length 41.3 mm, last whorl length 26.9 mm, aperture length (without canal) 16.0 mm, diameter 16.5 mm. In the largest specimen studied, shell length reaching 43 mm.

Anatomy

Two specimens examined: MNHN-IM-2013-61636, male, and MNHN-IM-2013-61637, female, sequenced paratype (similar in both studied specimens). Soft body partly extracted from the shell. Head medium large, with two long tentacles and large black eyes on lobes at bases of tentacles. Mantle similar to that of Phaenomenella samadiae n. sp. Penis flattened, with seminal papilla situated on its top and surrounded by circle fold of skin ( Fig. 8B ).

Digestive system. Proboscis almost completely inverted into rhynchodaeum ( Fig. 8D , pr). Several bands of proboscis retractors muscles attached to middle part on both sides of rhynchodaeum ( Fig. 8 D-F, prr). Buccal mass slightly shorter than retracted proboscis ( Fig. 8C , bm), attached to its walls by multiple odontophoral retractors ( Fig. 8C , odr). Radula lying in middle of buccal mass and attached to proboscis walls by median retractor ( Fig. 8C , mrr).

Anterior oesophagus straight, following along ventral side of proboscis ( Fig. 8E , aoe). Valve of Leiblein ( Fig. 8D, E , vl) medium large, coniform, situated immediately before nerve ring ( Fig. 8D , nr). Salivary glands medium-large (about 0.3 proboscis length), fused ventrally beneath nerve ring ( Fig. 8E, F , sg), with very thin strongly convoluted salivary ducts following along anterior oesophagus. Gland of Leiblein medium in size ( Fig. 8D, E , gl), following along posterior oesophagus and anterior aorta. Stomach rather large, spanning about 0.4 whorl ( Fig. 8G ). Posterior mixing area (pma) twice larger than in Phaenomenella samadiae , posterior oesophagus and intestine medium wide.

REMARKS

The new species is highly variable in shell shape. Some of the specimens are much more slender ( Fig. 7D, I, G ) and the axial ribs are either very weak or obsolete. The specimen with no axial ribs was collected at a maximal depth (1634-1683 m), but there is not clear correlation with depth, since syntopic specimens can have strong or weak axial ribs. Nevertheless the molecular data clearly indicates the conspecifity of “typical” angulated specimens with well-developed ribs and smooth ones. The specimens collected at greater depth have the protoconch and upper teleoconch whorls more eroded or missing. In general shape the new species has some resemblance to P. mokenorum Fraussen, 2008 from the Andaman Sea, differing in better pronounced axial ribs in later teleoconch whorls and more attenuated narrow siphonal canal. Also P. nicoi n. sp. has smaller size (maximal shell length 42 mm versus 55.6 mm in P. mokenorum ).

Figures

FIG. 5. — Radulae of Phaenomenella spp.A, B, Phaenomenella samadiae n. sp.; holotype,MNHN-IM-2013-61617 (shell on Fig. 4A-C) (A); MNHN-IM-2013-61674 (shell on Fig. 4 E, F) (B); C-F. Phaenomenella nicoi n. sp.; C, holotype, MNHN-IM-2013-61585 (shell on Fig. 7A-C); D, MNHN-IM-2013-59398 (shell on Fig. 7D); E, MNHN-IM-2013-61639 (shell on Fig. 7E); F, MNHN-IM-2013-61673 (shell on Fig. 7I). Scale bars: 100 μm.

FIG. 7. — Shells of Phaenomenella nicoi n. sp.: A-C, holotype, MNHN-IM-2013-61585, SL 41.1 mm; D, ZHONGSHA 2015, st. CP4157, sequenced spm, MNHN- IM-2013-59398, SL 37.5 mm;E, ZHONGSHA 2015,st. CP4133,sequenced spm,MNHN-IM-2013-61639, SL 43.2 mm;F, AURORA 2007,st. CP2685,sequenced spm, MNHN-IM-2007-34639, SL 34.7 mm; G, AURORA 2007, st. CP2685, not-sequenced spm, MNHN-IM-2007-34644, SL 38.7 mm; H, ZHONGSHA 2015, st. CP4133, sequenced spm, MNHN-IM-2013-61637, SL 30.6 mm (anatomy studied); I, ZHONGSHA 2015, st. CP4134, sequenced spm, MNHN-IM-2013-61673, SL 42 mm; J, ZHONGSHA 2015,st. CP4133,not-sequenced spm, MNHN-IM-2013-61636, SL 40.2 mm (anatomy studied); K, L, ZHONGSHA 2015, st. CP4132, not-sequenced spm, MNHN-IM-2013-61592, 39.1 mm; L, enlarged protoconch. Scale bars: A-K, 20 cm; L, 1 mm.

FIG. 8. — Anatomy of Phaenomenella nicoi n. sp.: A-D, MNHN-IM-2013-61636, male; E-G, MNHN-IM-2013-61637, female: A, soft body removed from the shell; B, penis; C, proboscis, opened dorsally; D, foregut,right lateral view; E, foregut,right lateral view, right salivary gland displaced; F, foregut,right lateral view, right salivary gland in original position; G, stomach, outer view. Abbreviations: see material and methods. Scale bars: 5 mm.