Homalocantha ninae, Merle & Garrigues, 2011

Merle, Didier & Garrigues, Bernard, 2011, Description of four new species of Muricidae (Mollusca, Gastropoda) from the Philippines and the Caribbean area, Zoosystema 33 (4), pp. 557-575 : 562-568

Homalocantha ninae n. sp.

( Figs 1 E-H; 2C, D)

TYPE MATERIAL. — Philippines. Cebu, Olango Island, 10-20 m deep, syntype 1 ( MNHN. IM.24628) (H: 25 mm). — Cebu, Calituban Island, syntype 2 ( MNHN. IM.24629) (H 37.8 mm).

TYPE LOCALITY. — Philippines. Cebu, Olango Island, 10-20 m deep.

OTHER MATERIAL EXAMINED. — Philippines. Cebu, Olango Island, 12-30 m deep, 2 specimens (Coll.

BG). — Balicasag Island, 6 specimens (Coll. BG). — Calituban Island, 2 specimen (1 Coll. BG and 1 Coll. GG). — Mactan Island, 9-12 m deep, 3 specimens (Coll. BG). — Samal Island, Punta Pait, 20-60 m deep, 2 specimens (Coll. BG). — Samar Sea, Baliran Island,

1 specimen (Coll. BG). — Davao Island, 2 specimens (Coll. GG).

ETYMOLOGY. — Named in honour of Nina Merle.

COMMENTS. — As this species is best defined by its growth series, we prefer to designate two syntypes, in respect of ICZN ( ICZN 1999: Article 72.3, rather than a holotype. The type series includes an intermediate-sized juvenile (syntype 1) and an adult specimen (syntype 2). ICZN Article 72.3 states: “Name-bearing types must be fixed originally for nominal species-group taxa established after 1999. A proposal of a new nominal species-group taxon after 1999 (unless denoted by a new replacement name (nomen novum) [Arts. 16.4, 72.7]), must include the fixation of a holotype [Art. 16.4] (see Article 73.1) or syntypes [Art. 73.2]. In the case of syntypes, only those specimens expressly indicated by the author to be those upon which the new taxon was based are fixed as syntypes ”.

DESCRIPTION OF SYNTYPE MNHN.IM.24628 (JUVENILE)

Protoconch broken.

Teleoconch of three whorls, 25.1 mm high, 16.5 mm wide. Spire very low, of two whorls, earliest teleoconch whorl flat, penultimate whorl inflated. Last whorl 94.2% of shell height. Apical angle 120° excluding spines, 135° including spines. Spiral sculpture of rounded primary cords. Primary cord spines with scabrous sculpture. On penultimate whorl, IP and P1 spines welded. On last whorl, IP and P1 spines well-developed, slightly deviated, P2, P3 and P4 spines well-developed, P5 and P6 spines smaller than P4 spine; P6 situated on base of siphonal canal, but not atrophied; ADP and MP spines developed, ABP spine smaller than MP spine, EAB1 spine smaller than ABP spine. Longest cord spines (on IP, P1, P2, ADP and MP) distally palmate. Secondary cords s2, s3, s4, s5, s6, ads and ms present. Tertiary cords present. Six varices present from the first to the last (third) whorl. Varices concave on two earliest whorls, convex on third whorl. Aperture oval, 24.2% of diameter (including spines), 79.7% of total height. Columellar lip smooth, slightly adherent. No anal sulcus. Siphonal canal inclined to right, 55.8% of total height. Two earliest whorls white; last whorl: at first, appearance of a dark brown band on P3; later, all primary cords dark brown, except IP; fi- nally, appearance of convex, dark brown varices, intervariceal space dark brown.

DESCRIPTION OF SYNTYPE MNHN.IM.24629 (ADULT)

Protoconch of two convex whorls. Teleoconch of four whorls, fusiform, 37.8 mm high, 25.7 mm wide. Spire of three whorls, earliest two whorls flat, penultimate whorl high, constricted at base and disjunct from last whorl, overall funnel-shaped. Last whorl 74% of teleoconch height. Apical angle 110° (excluding spines), 135° (including spines). Spiral sculpture of rounded primary cords. IP and P1 spines fused on two earliest teleoconch whorls. On penultimate whorl, IP and P1 spines reduced; on last whorl, IP and P1 spines poorly developed on varices, except well-developed on terminal varix.On terminal varix, IP, P1, P2, P3 and P4 spines welldeveloped, P5 and P6 spines atrophied, P5 spines shorter than P6, P6 situated on base of siphonal canal; ADP and MP spines well-developed, ABP spine shorter than MP spine, EAB1 spine shorter than ABP spine. Longest cord spines (on P1, P2, P3, P4, ADP and MP) distally palmate, each with two small digitations. Five varices present from first to last whorl. Varices on two last whorls convex. Terminal variceal expansion (outer lip) on convex part of whorl producing webbed shape to last varix. Aperture oval, 21% of diameter (including spines), 68% of shell height. Columellar lip smooth, slightly adherent. No anal sulcus. Outer lip finely crenulate and lirate within. Siphonal canal inclined to right, 47% of total height. On penultimate whorl, varices dark brown, intervarices whitish; on last whorl, varices and distal part of intervarices dark brown, proximal part of intervarices whitish. Operculum subcircular; nucleus lateral, to right of centre.

INTERSPECIFIC COMPARISONS

Homalocantha ninae n. sp. may be compared to H. scorpio ( Figs 3 A-D; 4A, B), H. pisori ( Figs 3 E-H; 4C, D), H. vicdani ( Figs 5 A-D; 6A, B) and H. dondani ( Figs 5 E-H; 6C, D).

Homalocantha scorpio versus H. ninae n. sp.

Juvenile specimens of H. scorpio differ from those of H. ninae n. sp. by their concave intervariceal spaces, by their higher spire and by the dark brown colour present only on the varices, the wide intervariceal spaces being white. Adult specimens of H. scorpio have concave intervariceal spaces, instead of convex ones in H. ninae n. sp., and have cord spines developed on the varices of the last whorl, whereas they are short and poorly developed in H. ninae n. sp. The terminal varix is similar in both species. The number of varices on juveniles is six in H. ninae n. sp. (two specimens) and varies from six to eight in H. scorpio (13 specimens). The number of varices on adults is five in H. ninae n. sp. (two specimens) and varies from six to seven in H. scorpio (14 specimens).

Homalocantha pisori versus H. ninae n. sp.

Juvenile specimens of H. pisori differ from those of H. ninae n. sp. by their concave intervariceal spaces. On the third whorl, the primary cord spines IP and P1 are hypertrophied, welded and just separated by an acute angle in H. pisori , while IP and P1 spines are not hypertrophied in H. ninae n. sp. On the fourth whorl, IP, P1 and P2 are welded proximally in H. pisori , while P2 is not welded proximally to IP and P 1 in H. ninae n. sp. The last whorl of adults of H. pisori bears flat intervariceal spaces and has cord spines developed, whereas that of H. ninae n. sp. has convex varices and reduced spines. From the juvenile to the adult, the shells of H. pisori differ by their pale tan colour. The terminal varix of H. pisori resembles that of H. ninae n. sp., but IP, P1 and P2 are better developed in H. pisori , whereas IP to P4 are all similarly developed in H. ninae n. sp.

Homalocantha vicdani versus H. ninae n. sp.

Juvenile specimens of H. vicdani differ from those of H. ninae n. sp. by their concave intervariceal spaces. On the third whorl, primary cord spines on IP and P1 are hypertrophied and welded in H. vicdani and a scabrous microsculpture appears in this species, whereas it is lacking in H. ninae n. sp. The last whorl of adults of H. vicdani has a shouldered form, with concave intervariceal spaces and with cord spines developed, whereas that of H. ninae n. sp. has a rounded form, convex varices and reduced spines. H. vicdani differs further in its ochre colour. The terminal varix is similar in both species.

Homalocantha dondani versus H. ninae n. sp.

Juvenile specimens of H. dondani differ from those of H. ninae n. sp. by their concave intervariceal spaces, shouldered whorls and higher spire. The last whorl of adults of H. dondani has small intervariceal nodules, which are missing in H. ninae n. sp. As in H. scorpio , H. pisori , and H. vicdani , the varices of the last whorl of H. dondani have cord spines developed. From the juvenile to the adult, the shell colour of H. dondani is creamy white with pale rusty varices. The terminal varix is similar in both species.

Figures

FIG. 1. — Homalocantha granpoderi n. sp. and H. ninae n. sp., primary cords in dorsal and apical views: A-D, H. granpoderi n. sp.; A, paratype MNHN.IM.24627 (H: 24 mm); B, Coll. GG, Palawan, Philippines (H: 39.9 mm); C, holotype MNHN.IM.24626 (H: 47 mm); D, paratype (apical view); E-H, H. ninae n. sp.; E, syntype 1 MNHN.IM.24628 (H: 25 mm); F, Coll. BG, Balicasag Island, Philippines (H: 26.6 mm); G, syntype 2 (H: 37.8 mm); H, syntype 1 MNHN.IM.24629 (apical view). Scale bars: 10 mm.

FIG. 3. — Homalocantha scorpio (Linnaeus, 1758) and H. pisori d’Attilio & Kosuge, 1989, primary cords in dorsal and apical views: A-D, H. scorpio; A, Coll. BG, 10 m, Bantayan Island, Cebu, Philippines (H: 24.7 mm); B, Coll. BG, 10 m, Calituban, Bohol, Philippines (H: 36.8 mm); C, Coll. BG, Calituban, Philippines (H: 51.6 mm); D, Coll. BG, Balut Island, Mindanao, Philippines (H: 28 mm) (apical view);E-H, H. pisori; E, Coll. BG,Philippines (H: 14 mm);F, H (apical view), Coll.BG, Davao at 80-120 m deep, Philippines (H: 29 mm); G, Coll. BG, Bohol at 20 m deep, Philippines (H: 40 mm). Scale bars: 10 mm.

FIG. 5. — Homalocantha vicdani d’Attilio & Kosuge, 1989 and H. dondani d’Attilio & Kosuge, 1989, primary cords in dorsal and apical views: A-D, H. vicdani; A, Coll. BG, Camiguin, at 30 m deep, Mindanao, Philippines (H: 20 mm); B, D (apical view), Coll. BG, Mactan Island at 12 m deep, Philippines (H: 23 mm); C, Coll. BG, Calituban Island, Philippines (H: 36.2 mm); E-H, H. dondani; E, Coll. BG, Philippines (H: 19.3 mm); F, H, apical view, Coll. BG, Philippines (H: 31.7 mm); G, Coll. BG, Calituban Island at 20 m deep, Bohol (H: 30 mm). Scale bars: 10 mm.