Mioawateria vivens, Morassi, Mauro & Bonfitto, Antonio, 2013

Morassi, Mauro & Bonfitto, Antonio, 2013, Three new bathyal raphitomine gastropods (Mollusca: Conoidea) from the Indo-Pacific region, Zootaxa 3620 (4), pp. 579-588 : 584-585

Mioawateria vivens sp. nov.

Fig. 1 .H–N

Type material: Holotype (MZB49755) and 23 paratypes (seven coated) (MZB49756), 1 paratype MNHN (MNHN25732), 1 paratype (ZMA.MOLL.408925),

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

Material examined: 26 dd + 2 fragments 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 (including holotype and 23 paratypes MZB, 1 paratype MNHN and 1 paratype ZMA); 18 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 (MZB 49757); 29 dd from Red Sea, stn RED SED 92/4, from 14°45'52"N, 42°18'65"E to 14°45'66"N, 42°18'92E, 776–781 m (MZB 49758)

Description: Shell biconic (b/l 0.51–0.58; a/l 0.47–0.53) of up to 5 teleoconch whorls which are strongly shouldered above mid-whorl height on spire, sutural ramp with moderately prominent subsutural fold; last whorl broadly excavated, with short neck. Axial sculpture of narrow, opisthocline ribs extending from shoulder angle to lower suture on spire whorls, and across base (but not onto neck) on last whorl. Axial ribs of rounded-triangular cross-section, with interspaces considerably wider than them. First teleoconch whorl with 13–15 ribs, increasing in number to 15–19 on penultimate and 19–23 on last whorls. Sutural ramp with narrow, prosocline riblets, more numerous than axial ribs, extending from upper suture to shoulder angle on early whorls, with a tendency to be confined to subsutural fold on later whorls. Spiral sculpture commencing as a cord on shoulder, joined during growth by low, flat-topped cords. Penultimate whorl with 3–4 spiral cords below the shoulder cord; last whorl with additional 18–22 cords on base and neck. Under SEM a microsculpture of dense, minute pustules, partially fused together, forming irregularly spirally aligned at level of shoulder and lower part of sutural ramp (fig. 1.N). Aperture pyriform, columella almost straight above, gently curved to left below, forming a short, wide siphonal canal. Inner lip thinly callused. Outer lip with a very shallow anal sinus, its apex on shoulder. Protoconch conical of 3.5 whorls; protoconch I ( Fig. 1 .M) covered with minute, dense spiral threads crossed by even finer axial threads to form minute plicules; protoconch II ( Fig. 1 .K) sculptured by opisthocline, opisthocyrt axial riblets forming diagonal cancellation with oblique threads in abapical two-thirds. Diameter: 0.38–0.43 mm. Shell translucent white with yellowish apex. Dimensions: Holotype: 6.3 x 3.3 mm, aperture height 2.9 mm; smallest paratype: 5.3 x 2.8 mm, aperture height 2.6 mm; largest paratype: 6.4 x 3.4 mm, aperture height 3.2 mm.

Etymology: vivens (Latin) = living, alluding to the fact that the new species is morphologically so close to the Miocene-Pliocene Mioawateria personata Powell, 1942 that one can speculate that it actually represents a living offshoot of the New Zealand species.

Remarks: Mioawateria vivens sp. nov. differs distinctly from the widely distributed M. extensaeformis (Schepman, 1913) , the only species belonging to Mioawateria species also reported from the Gulf of Aden, in its smaller dimensions (up to 6.4 mm vs. 8.2–9.9 mm in length), strongly shouldered whorls well above mid-whorl and absence of somewhat “crisp” axials on the sutural ramp. Actually, the new species is morphologically extremely similar in shape and sculpture to Mioawateria personata Powell, 1942 from which it differs in possessing whorls shouldered well above mid-whorl rather than at or near mid-whorl height, less opisthocline axial ribs and a shorter neck. Mioawateria vivens sp. nov. differs from the Italian Pliocene-Early Pleistocene Genotia brevis pliorecens Ruggieri, 1957 in possession a less produced and excavated base, definitely squarely shouldered whorls, and less opisthocline axial ribs. Furthermore, judging from material stored in MZB, specimens of Genotia brevis pliorecens are characterized by a remarkable reduction in the number of axial ribs on later teleoconch whorls as compared to earlier growth stages (from up to 30 on early 1–1.5 whorls to 15–16 on later). Such reduction in ribbing during ontogenesis is not observed in Mioawateria vivens sp. nov. in which the number of axial ribs increases gradually during growth (from 13–15 on the first teleoconch whorl to 19–23 on the last one).

Figures

FIGURE 1. A – G. Taranis adenensis sp. nov. A. Holotype, scale bar 800 μm, Gulf of Aden, stn RED SED S 92 / 1 (MZB 49753); B – G. Paratype, Gulf of Aden, stn RED SED 92 / 1 (MZB 49754); B. Frontal view, scale bar 600 μm; C. Apical view, scale bar 400 μm; D. Penultimate whorl, scale bar 200 μm; E. Surface microsculpture, scale bar 40 μm; F – G. Protoconch, scale bar 100 μm. H – N. Mioawateria vivens sp. nov. H. Holotype, 6.3 x 3.3 mm, Gulf of Aden, stn RED SED 92 / 1 (MZB 49755); I – N. Paratype, Red Sea, stn RED SED 92 / 4 (MZB 49756); I. Frontal view, scale bar 1 mm; J. Apical view, scale bar 1 mm; K – L. Protoconch, scale bar 100 μm; M. Detail of protoconch I, scale bar 50 μm; N. Surface microsculpture, scale bar 50 μm. O – T. Holotype of Awheaturris lozoueti sp. nov., Philippines, AURORA 2007 stn CP 2682 (MNHN 25730); O. Frontal view, scale bar 1 mm; P. Apical view, scale bar 1 mm; Q. Penultimate whorl, scale bar 500 μm; R. Surface microsculpture, scale bar 80 μm; S – T. Protoconch, scale bar 200 μm.