Pyrunculus sp.

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 747-748

Pyrunculus sp.

Figs 79E-G, 82

MATERIAL EXAMINED. — Philippines. MUSORSTOM 3: stn DR 94, 13°47’N, 120°03’E, 842 m, 5 dd; stn CP 106, 13°47’N, 120°30’E, 640-668 m, 6 dd (Figs 79E, F) .

Indonesia. KARUBAR: stn CP 71, Tanimbar Islands, 08 °38’S,

131°44’E, 477-480 m, 17 dd (Fig. 79G); stn CP 75, 08°46’S, 131°36’E, 451-452 m, 5 dd; stn CP 87, 08°47’S, 130°49’E, 1017- 1024 m, 3 lv, 1 destroyed to dissect the gizzard plates; stn CP 91, 08°44’S, 131°05’E, 884-891 m, 1 dd.

DISTRIBUTION. — Material herein collected from Indonesia and the Philippines (Fig. 82), in 452-1017 m, live in 1017-1024 m .

DESCRIPTION. — Shell morphology. Length 4 mm, width 1.5 mm (largest specimen examined). Shell fragile, oval to pyriform, with the widest region near the anterior end (Fig. 79E). Only 1 whorl visible, forming the entire shell, except for a small visible portion of the top of the spire, which is encircled by the outer edge of the apical umbilicus. Apex rounded, depressed, umbilicate (Figs 79F), with the aperture lip rising from the left side. The aperture lip forms a pointed, conspicuous wing connected to the columellar margin. Anterior end of the shell rounded. Umbilicus closed. Aperture long, wide anteriorly, narrowing abruptly at about 1/2 of its length. Columellar margin thickened, with no folds. Sculpture of faint growth lines. Colour uniformly dirty white to pale cream.

Anatomy. The digestive system contains 3 irregular, unequal gizzard plates, one larger and the other two smaller, with 2 tubercles each (Fig. 79G). There is no radula.

REMARKS. — Pyrunculus sp. differs from Pyrunculus pyriformis (A. Adams in Sowerby, 1850) in shell morphology and anatomy. Specimens of Pyrunculus sp. have a more oval, less pyriform shell with a more conspicuous apical wing. The gizzard plates of P. pyriformis are more triangular compared to those of Pyrunculus sp. , which are more irregular.

This species is included in the genus Pyrunculus based on the presence of 3 unequal gizzard plates with only 2 tubercles on each, and a more or less pyriform shell with a deep apical umbilicus.