Genaxinus eumyarius ( Sars M., 1870 )

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 : 34

Genaxinus eumyarius ( Sars M., 1870)

Fig. 7 g–i

Axinus eumyarius Sars M., 1870 (p. 87, pl. 12, figs. 7–10).

Axinus eumyarius M. Sars—Jeffreys 1881 (p. 703).

Leptaxinus eumyarius ( M. Sars, 1870) — Nordsieck 1969 (p. 81, pl. 13, fig. 48.20). Axinulus eumyarius (Sars) — Di Geronimo 1974 (p. 156).

Thyasira (Axinulus) eumyaria ( M. Sars, 1870) — Payne & Allen 1991 (p. 529, figs. 76–77); Giribet & Peñas 1997 (fig. 105). Axinulus (Genaxinus) eumyarius ( M. Sars, 1870) — Oliver et al. 2002 (pp. 52, 68; pls. 5, 21; text-fig. 6). Leptaxinus eumyarius ( Sars M., 1870) — Repetto et al. 2005 (p. 310, top right fig.). Genaxinus eumyarius (M Sars, 1870) — Oliver et al. 2016 (online resource).

Diagnostic characters. High subquadrangular shell; two strong, elevated myophores; anterior myophore wide and drop-shaped; posterior myophore narrow and long. Prodissoconch: shell type ST-2D; length about 120 µm; roundish D-shaped outline; convex profile; surface with a net-like sculpture of wrinkles, more raised on the cicatrix area; P-2 replaced by shell lip; transition to the nepioconch well marked.

Remarks. We follow Oliver & Levin (2006) in assigning this species to Genaxinus Iredale, 1930 , rather than Axinulus Verrill & Bush, 1898 , which seems to have normal (i.e. not raised) adductor scars.

Occurrence. Box-corer samples BC04 (1 specimen), BC66 (1), BC72 (7); core BC72 (2). Maximum height: 2 mm.

Distribution and habitat. The species is reported to be widespread in all the Atlantic and the Mediterranean, from 50 to over 2600 m, lacking the symbionts co-occurring with many lucinid species ( Payne & Allen 1991; Buhl-Mortensen & Høisaeter 1993; Oliver et al. 2002, 2010)

Fossil record. Pliocene of Sicily ( Monterosato 1872).

Figures

FIGURE 7. a – c: Axinulus alleni (Carrozza, 1981); RV, sample BC 72, scale bars: 1 mm (a – b), 0.1 mm (c, prodissoconch); d – f: Thyasira flexuosa (Montagu, 1803); RV (e, f) and LV (d), sample BC 72, scale bars: 2 mm (d – e), 0.1 mm (f, prodissoconch); g – i: Genaxinus eumyarius (Sars M., 1870); RV (h, i) and LV (g), sample BC 72, scale bars: 1 mm (g – h), 0.1 mm (I, prodissoconch); j – l: Leptaxinus subovatus (Jeffreys, 1881); RV, sample BC 72, scale bars: 1 mm (j – k), 0.1 mm (l, prodissoconch); m – o: Mendicula ferruginosa (Forbes, 1844); RV, sample BC 72, scale bars: 1 mm (m – n), 0.1 mm (o, prodissoconch).