Otitoma neocaledonica, Morassi & Nappo & Bonfitto, 2017

Morassi, Mauro, Nappo, Andrea & Bonfitto, Antonio, 2017, New species of the genus Otitoma Jousseaume, 1898 (Pseudomelatomidae, Conoidea) from the Western Pacific Ocean, European Journal of Taxonomy 304, pp. 1-30 : 15-16

Otitoma neocaledonica sp. nov.

urn:lsid:zoobank.org:act:0502F4E9-D944-4F48-8CFD-32FA40FC5D40

Fig. 4 G–O

Etymology

The specific epithet alludes to the origin of the type material ( New Caledonia).

Type material

Holotype

NEW CALEDONIA: Montrouzier Expedition , Stn 1322, Koumac, Deverd Passage, 20°45.2 ′ S, 164°15.2 ′ E, 53–71 m ( MNHN IM-2000-32598 ).

Paratypes

NEW CALEDONIA: paratypes 1–4, same data as holotype ( MNHN IM- 2000-32599); paratypes 5–6, Montrouzier Expedition, Stn 1309, Koumac Lagoon, l’îlot Kendek Passage, 20°40.5 ′ S, 164°13.4 ′ E, 18 m ( MNHN IM- 2000-32600); paratype 7 (coated, MZB 60213) and paratypes 8–11 ( MNHN IM- 2000-32601), Montrouzier Expedition, Stn 1314, Koumac Lagoon, 20°39.8 ′ S, 164°15.3 ′ E, 30– 63 m.

Additional material examined

NEW CALEDONIA: 5 spms, Montrouzier Expedition, Stn 1322, Koumac, Deverd Passage, 20°45.2 ′ S, 164°15.2 ′ E, 53–71 m; 6 spms, Montrouzier Expedition, Stn 1314, Koumac Lagoon, 20°39.8 ′ S, 164°15.3 ′ E, 30–63 m; 1 spm, Montrouzier Expedition, Stn 1313, Koumac Lagoon, 20°38.8 ′ S, 164°15.6 ′ E, 13– 38 m.

Description

Shell cylindric-fusiform (b/l 0.35–0.40; a/l 0.45–0.52), somewhat pupoid. Teleoconch whorls up to 3¾–5½, moderately convex, with periphery just posterior to mid-whorl. Suture shallow, bordered by two closely spaced spiral threads demarcated by a wide, shallow and concave sutural ramp. Axial ribs rather straight, opisthocline and rounded, equal to or wider than intercostal space, developing mainly in peripheral region, not reaching suture. 12–15 axial ribs on penultimate whorls; on last whorl 11–17 ribs, but reduced to 8–10 in specimens with ribs fading on last portion of whorl. Sculptured by widely-spaced spiral cords, crossing low axial ribs, not forming distinct nodules. Earliest two teleoconch whorls with 2–3 spiral cords between sutural ramp and whorl base, increasing to 4–6 on later two whorls. Sutural ramp with 2 main cords on abapical side and 1–2 finer cords posterior to these. Last whorl with 12–17 main spiral cords, interstices with none to 1–2 secondary cords and with finer interstitial threads on base and rostrum. Under SEM ( Fig. 4 J–K) intervals between main cords seen to be sculptured by 2–4 rather inconspicuous, microscopic spiral threads and numerous granules. Entire surface covered by coarse axial growth lines. Aperture rather narrow and almost linear, but constricted at entrance to siphonal canal. Siphonal canal relatively wide, expanding slightly distally, oblique, not notched terminally. Inner lip with moderately thin callus, but distinct parietal pad. Outer lip edge sharp, preceded by a wide, low, rounded varix. Anal sinus moderately deep, apically rounded, asymmetrically U-shaped, with strongly constricted opening. Stromboid notch distinct. Protoconch domed to papilliform, of 1¼–1¾ whorls; first whorl smooth, last portion with numerous irregular axial riblets, diameter 0.67–0.88 mm ( Fig. 4 L–M). Protoconch and earlier teleoconch whorls violaceous in some specimens ( Fig. 4 O–N). Two color forms: a) white or yellowish-white tinged with light brownish-orange on sub-sutural ramp, base and tip of rostrum, and aperture rimmed with darker brownish orange; b) a uniform light brown (paratype 6).

Dimensions

Holotype: 8.2 × 3.0 mm, aperture height 3.85 mm. Paratype 7 (smallest paratype): 5.5 × 2.1 mm, aperture height 2.75 mm; paratype 9 (largest paratype): 7.4 × 2.7 mm, aperture height 3.6 mm.

Remarks

Otitoma neocaledonica sp. nov. is morphologically similar to O. oneili (Barnard, 1958) , but differs from the latter in numerous characters. The new species is smaller in length (up to 8.2 mm vs up to 12.3 mm in maximum length), with different proportions (a/l 0.45–0.52 vs 0.32–0.41), fewer secondary cords on the sub-sutural ramp and the presence of weaker, inconspicuous microscopic cords in the interspaces between the main cords. Otitoma neocaledonica sp. nov. has a different protoconch structure (domed-papilliform and of 1¼–1¾ whorls instead of bluntly conical, of about 3 whorls). Furthermore, the protoconch and the earlier teleoconch whorls are violaceous in most specimens of Otitoma neocaledonica sp. nov., a feature not reported in O. oneili ( Kilburn 1995 and pers. obs).