Iredalea adenensis, Morassi, Mauro & Bonfitto, Antonio, 2013

Morassi, Mauro & Bonfitto, Antonio, 2013, Four new African turriform gastropods (Mollusca: Conoidea), Zootaxa 3710 (3), pp. 271-280 : 274

Iredalea adenensis sp. nov.

Figures 1 . I–K

Type material. Holotype (MZB 60072) and 3 paratypes (MZB 60073); 1 paratype (MNHN-IM- 2012-2532).

Type locality. Offshore Gulf of Aden, trawled by local fishermen at 200–400 m in 1994.

Material examined. The type material.

Description. Shell rather solid (fig. I–J), narrowly claviform (b/l 0.43–0.45; a/l 0.39–0.46) with high, acute spire and short base. Protoconch somewhat conical of 1¾ whorls. Protoconch diameter: 0.75 mm (holotype). Teleoconch of up to 7 whorls with slight, rounded shoulder at about mid-whorl height, sutural ramp concave, suture shallow. Sculpture of numerous, narrow axial ribs (fig. K), as broad as interspaces, opisthocline with a prosocline inflexion on sutural ramp; sixteen to 17 axial ribs on antepenultimate and penultimate whorl, 17–18 on last whorl. Adapical part of whorl surface sculptured on last two whorls by indistinct spiral lines; 7–8 spiral grooves, with a tendency to form rectangular granules where crossing axial ribs, on the rostrum. Aperture oblong-ovate, columella relatively straight with a moderately thick callus, its outer edge slightly raised; parietal region concave, parietal pad filling posterior angle of aperture, constricting anal sinus. Siphonal canal short, broad, slightly obliquely notched. Outer lip with a distinct stromboid notch in the abapical part, almost straight in lateral view, with a cutting edge. Anal sinus moderately deep, openly and asymmetrically U-shaped, directed slightly adapically. Color yellowishwhite with a single brown band margining abapical suture on penultimate whorl, occupying the median zone on the last whorl; columella and protoconch white. Dimensions: Holotype: 17.2 x 7.7 mm, aperture height 6.8 mm; largest paratype (MZB): 20.2 x 9.1 mm, aperture height 9.3 mm; smallest paratype (MZB): 14.7 x 6.4 mm, aperture height 6.6 mm.

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

Remarks. This new species represents the first record of the genus Iredalea from the Gulf of Aden. Kilburn (1988) reported two Iredalea species from southern Africa, namely Iredalea inclinata (Sowerby, 1893) and I. exilis (Pease, 1868) . Iredalea adenensis sp. nov. is comparable in size to I. inclinata , reported from Mauritius and Reunion Island to Natal, but has more numerous axial ribs (16–18 versus 12–15 on later two teleoconch whorls), higher periphery (median rather than at about abapical third of whorl), fewer protoconch whorls (1¾ versus 2 ½), deeper anal sinus and very different colour pattern. In particular, I. adenensis has a yellowish-white shell with a single brown band margining abapical suture on penultimate whorl occupying the median zone on the last whorl, while the shell of I. inclinata is patterned with deep brown forming three bands on last whorl (Kilburn, 1988: 187). Weinkauff in Weinkauff & Kobelt, 1876 described Pleurotoma polygonalis from Zanzibar which, according to Kilburn (1988: 187), may prove to be an earlier name for Iredalea inclinata . The shell of Pleurotoma polygonalis was described as “ albida, zonis fuscis picta ” with “ flavidulo bifasciata ” aperture (page 100, pl. 21 figs 7,9). As remarked by Kilburn (1988), the original figure of Pleurotoma polygonalis is rather indistinct but the drawing in lateral view clearly shows two brown bands at level of aperture, thus differing from Iredalea adenensis which has a single brown band. Apart from the presence of spiral bands, the shell of I. adenensis is yellowish-white while that of P. polygonalis is patterned with brown (“ zonis fuscis picta ”). The new species resembles I. exilis Pease, 1860 reported from Polynesia to southern Africa, in possessing a brown band in the median zone of last whorl but otherwise differs mainly in its much larger shell (up to mm 20 mm versus 8 mm or less), shape (claviform rather than pupoid) and in possessing a paucispiral protoconch (1¾ versus about 4 whorls).

Figures

FIGURE 1. A – H. Tropidoturris vizcondei sp. nov. A – B. Holotype (MNHN 26614), 11.1 x 4.3 mm. C – H. Paratype (MZB 60071). C. Shell, scale bar 1 mm. D. Penultimate whorl, scale bar 500 µm. E. Surface microsculpture, scale bar 40 µm. F – G. Protoconch, scale bar 200 µm. H. Microsculpture of protoconch, scale bar 100 µm. I – K. Iredalea adenensis sp. nov. I – J. Holotype (MZB 60072), 17.2 x 7.7 mm. K. Penultimate whorl. L – P. Buchema shearmani sp. nov. L – M. Holotype (MZB 60073), 9.9 x 3.5 mm. O. Protoconch. P. Detail of penultimate whorl. Q – S. Crassispira somalica sp. nov. Q – R. Holotype (MZB 60076), 21 x 8.9 mm. S. Penultimate whorl.