Callostracon thyrrenicum ( Smriglio & Mariottini, 1996 )

Negri, Mauro Pietro & Corselli, Cesare, 2016, Bathyal Mollusca from the cold-water coral biotope of Santa Maria di Leuca (Apulian margin, southern Italy), Zootaxa 4186 (1), pp. 1-97 : 81

Callostracon thyrrenicum ( Smriglio & Mariottini, 1996)

Fig. 18 m–o

Colostracon thyrrenicum Smriglio & Mariottini, 1996 (p. 184, figs. 1–5). Callostracon thyrrenicum Smriglio & Mariottini, 1996 — Repetto et al. 2005 (p. 254, mid-left fig.); Repetto & Bianco 2012 (p. 40, fig. 4).

Diagnostic characters. Ovate shell; drop-shaped aperture; thin parietal callus deep inside the aperture; weak columellar fold; close-set spiral rows of oval pits connected in a chain-like pattern. Protoconch: heterostrophic, submerged, nearly globose; slightly more than 1 visible whorl; diameter about 700 µm; surface smooth; transition to the teleoconch marked by a thin orthocline lip.

Remarks. The specimens fully conform to the types figured by Smriglio & Mariottini (1996). The genus “ Callostracon ”, as used by Smriglio & Mariottini (1996) after Nordsieck (1972), is a subsequent incorrect spelling of Colostracon Hamlin, 1884 , a Mesozoic genus (cf. Bouchet 2012). The same generic name Callostracon was proposed by Repetto & Bianco (2012) for Mediterranean species.

Occurrence. Box-corer samples BC71 (2 specimens), BC72 (1); core BC52 (1). Maximum height: 5 mm.

Distribution and habitat. Callostracon thyrrenicum is distributed in the central Mediterranean, from the Northern Thyrrenian Sea to Malta, dwelling on coral banks and muddy bottoms at 400–600 m depth ( Smriglio & Mariottini 1996; Smriglio et al. 1998). It has been regarded as an element of the CB bathyal biocoenosis ( Smriglio & Mariottini 1996).

Fossil record. None recorded.

Figures

FIGURE 18. a – c: Turbonilla micans (Monterosato, 1875), sample BC 51, scale bars: 0.5 mm (a), 0.2 mm (b – c, protoconch); d – f: Graphis gracilis (Monterosato, 1874), sample BC 72, scale bars: 0.5 mm (d), 0.2 mm (e – f, protoconch); g – i: Crenilabium exile (Jeffreys, 1870), samples BC 67 (g) and BC 04 (h – i), scale bars: 2 mm (g), 0.2 mm (h – i, protoconch); j – l: Japonacteon pusillus (MacGillivray, 1843), sample BC 72, scale bars: 2 mm (j), 0.2 mm (k – l, protoconch); m – o: Callostracon thyrrenicum (Smriglio & Mariottini, 1996), sample BC 71, scale bars: 1 mm (m), 0.2 mm (n – o, protoconch).