Adeuomphalus densicostatus (Jeffreys, 1884)

Fig. 12 n–p

Homalogyra densicostata Jeffreys, 1884 [a] (p. 129, pl. 10, fig. 1).

Adeuomphalus ammoniformis G. Seguenza, 1876 — Smriglio et al. 1988 (p. 2, fig. 1); Giannuzzi-Savelli et al. 1994 (p. 106, fig. 349).

? Adeuomphalus ammoniformis Seguenza G., 1876 — Repetto et al. 2005 (p. 90, mid right fig.).

Adeuomphalus densicostatus (Jeffreys, 1884) — Kano et al. 2009 (p. 403, figs. 1A–E).

Diagnostic characters. Planispiral shell; aperture roundly subrectangular, higher than wide; convex outer lip; two spiral keels on base and apical side; the apical keel weaker, located halfway between suture and periphery; densely spaced, thin and sinuous axial riblets passing over the keels. Protoconch: planispiral; 1.25 whorls; diameter about 150 µm; sculpture of irregularly aggregated, somewhat star-shaped granules; transition to the teleoconch marked by a thin sinuous lip.

Remarks. Adeuomphalus ammoniformis Seguenza, 1876 [a] differs in having more quadrangular whorl section and aperture, almost straight riblets, and sharper keels located more peripherally and becoming finely nodulose at the intersections with the riblets.

Occurrence. Core BC72 (3 specimens). Maximum diameter: 0.9 mm.

Distribution and habitat. Adeuomphalus densicostatus is reported as living in the NE Atlantic, as far South as the Azores, and only as fossil from the Mediterranean; it is a bathyal (305–2175 m) radula-less gastropod, probably living associated with carnivorous sponges of the family Cladorhizidae and feeding on them, often near hydrothermal vents (Kano et al. 2009).

Fossil record. Pliocene and Pleistocene of Sardinia and southern Italy (Di Geronimo & Li Gioi 1980; Kano et al. 2009).