Horaiclavus adenensis, Bonfitto, Antonio & Morassi, Mauro, 2014

Bonfitto, Antonio & Morassi, Mauro, 2014, Two new Horaiclavus (Horaiclavidae, Conoidea) species from the Indo-Pacific region, Zootaxa 3821 (1), pp. 146-150 : 147

Horaiclavus adenensis sp. nov.

Figures 1A–L

Type material. Holotype ( MZB 60078), 8 paratypes ( MZB 60079), 1 paratype MNHN, 1 paratype ZMA, 1 paratype NHMUK, 1 NMNS, 1 ZMC, 1 ZRA, all from the type locality.

Type locality. Gulf of Aden (Indian Ocean), stn. RED SED 92/1, 11º55'95"N, 44º22'70"E to 11º55'82"N, 44º22'53"E, 795– 810 m.

Material examined. 15 dd from Gulf of Aden, stn. RED SED 92/1, from 11º55'95"N, 44º22'70"E to 11º55'82"N, 44º22'53"E, 795–810 m (holotype and 14 paratypes); 1 dd from Gulf of Aden, stn. RED SED 92/2, between 12º02'36"N, 44º29'53"E and 12º02'46"N, 44º30'82"E, 1395–1400 m (coated, MZB 60080).

Description. Shell claviform (b/l 0.48–0.51; a/l 0.40–0.42) ( Fig. 1A–C, E ) with a moderately high orthoconoid spire and a short, contracted and quite strongly tapering base. Protoconch papilliform of about 1¼–1½ smooth whorls ( Fig. 1I –J ) with a weak submedian keel near termination bordered by few spiral rows of granules ( Fig. 1K–L ). Maximum protoconch diameter 0.57 mm. Teleoconch of up to ca. 4½ whorls with shallowly impressed, slightly wavy suture. Whorls strongly convex, gradate; first whorl bluntly angled near middle, subsequent whorls with a well rounded shoulder above mid-whorl height on later two teleoconch whorls. Subsutural ramp is narrow, weakly concave on earlier two whorls, convex on later whorls. Axial sculpture of strong, slightly arcuate and weakly opisthocline folds, extending from suture to suture, weakening on subsutural ramp and fading on lower shell base. Axial ribs of rounded triangular crosssection, interspaces concave, broader than ribs. There are 10–11 axial ribs on last two teleoconch whorls. Spiral sculpture represented only by three weak threads on rostrum. Aperture is oval, with rather short siphonal canal. Anal sinus weak, just an insinuation of thin lip edge ( Fig. 1D ). Inner lip evenly curved, columellar part straight, parietal callus forming a weak pad. Under SEM the surface of the interior part of the inner lip is seen to be covered by squamiform pustules ( Fig. 1H ). Outer lip has a heavy varix behind thin lip edge. Shell glossy and white. Dimensions: Holotype: 4.5 x 2.3 mm, aperture height 1.9 mm. Largest paratype: 5.0 x 2.4 mm, aperture height 2.1 mm; smallest paratype of the series, probably a shell of an immature specimen with 3.8 teleoconch whorls: 3.8 x 1.9 mm, aperture height 1.6 mm.

Etymology. adenensis , alluding to the fact that the new species is described from the Gulf of Aden.

Remarks. Horaiclavus adenensis sp. nov. is characterized by its small size and presence of a submedian keel in the terminal part of the protoconch. Among its supposed congeners, it is comparable to Horaiclavus anaimus Sysoev in Fedosov & Kantor, 2008 in shape and number of protoconch whorls but differs from the latter mainly in its much smaller dimensions (up to 5 mm vs up to 12 mm in maximum length), more strongly convex spire whorls, spiral sculpture restricted to rostrum, shorter siphonal canal and presence of a weak keel in the terminal part of the protoconch, a feature not reported so far in any of its described congeners. The presence or absence of a keel in the protoconch is currently regarded as a doubtful feature in supraspecific classification; also we cannot exclude the possibility that SEM examination would show the presence of this feature in other Horaiclavus or Horaiclavus -like species. H. adenensis sp. nov. superficially resembles in shape, axial sculpture and presence of a carinate protoconch the shallow water Clavus costatus Hedley, 1922 (= Gracicliclava mackayensis Shuto, 1983 ), from Queensland ( Australia), type species of Graciliclava Shuto, 1983 , a genus currently regarded as closely related to and possibly a subgenus of Anacithara Hedley, 1922 ( Kilburn, 1994) , also included in the Horaiclavidae ( Bouchet et al., 2011) . However, according to Shuto (1983:11–12) the shell surface of Graciliclava costata ( Hedley, 1922) is sculptured by “dense and minute spiral lines” of different order of strength as in members of the genus Anacithara and the protoconch keel is stronger than in H. adenensis .

Figures

FIGURE 1. A – L. Horaiclavus adenensis sp. nov. A – B. Holotype, 4.5 x 2.3 mm, Gulf of Aden, stn. RED SED 92 / 1 (MZB 60078). C – D. Paratype, Gulf of Aden, stn. RED SED 92 / 1 (MZB 60079). C. Frontal view, scale bar 1 mm. D. Anal sinus, scale bar scale bar 100 µm. E – L. Paratype, Gulf of Aden, stn. RED SED 92 / 1 (MZB 60079). E. Frontal view, scale bar 1 mm. F. Apical view, scale bar 1 mm Protoconch, scale bar 100 µm. G. Microsculpture of the teleoconch; scale bar 100 µm. H. Inner lip prickly nodules, scale bar 10 µm. I – K. Protoconch, scale bar 100 µm. L. Submedian keel in the terminal part of the protoconch, scale bar 10 µm. M – T. Horaiclavus ordinei sp. nov. M – N. Holotype, 5.8 x 3.1 mm, Balicasag Island, Philippines (MZB 60081). O – P. Paratype, Balicasag Island, Philippines (MZB 60082). Frontal and lateral view, scale bar 1 mm. Q. Surface microsculpture of penultimate whorl, scale bar 500 µm. R. Apical view, scale bar 1 mm. S – T. Protoconch, scale bar 200 µm.