Malletia obtusa (Sars M. in Sars G. O., 1872 )

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 : 17

Malletia obtusa (Sars M. in Sars G. O., 1872)

Fig. 2 i–k

Yoldia obtusa Sars M. in Sars G.O., 1872 (p. 23, pl. 3, figs. 16–20).

Malletia obtusa M. Sars—Jeffreys 1879 (p. 586).

Malletia obtusa (M. Sars) — Verrill & Bush 1898 (p. 874, pl. 97, fig. 4).

Malletia obtusa (M. Sars, 1868) — Nordsieck 1969 (p. 14, pl. 2, fig. 03.20).

Malletia obtusa (Sars) — Di Geronimo & Panetta 1973 (p. 95, pl. 3, fig. 3).

Malletia obtusa G.O. Sars, 1878 — Sanders & Allen 1985 (p. 232, figs. 40–41). Pseudomalletia pianii Van Aartsen & Giannuzzi-Savelli, 1991 (p. 4).

Pseudomalletia pianii Van Aartsen & Giannuzzi-Savelli, 1991 — Giannuzzi-Savelli et al. 2001 (p. 54, fig. 50). Pseudomalletia pianii ( Van Aartsen & Giannuzzi-Savelli, 1991) — Repetto et al. 2005 (p. 284, mid left fig). Pseudomalletia obtusa ( G.O. Sars, 1878) — La Perna 2003 (p. 28, pl. 4, fig. 3).

Diagnostic characters. Flattened, subrectangular, markedly inequilateral shell with posterior side longer and wider; anterior side obtusely pointed; shallow external sulcus from the beak to the upper third of the posterior side, faintly bilobed in some specimens; outer surface with uneven growth markings. Prodissoconch: shell type ST-1A; P-1: length about 260 µm; ellipsoidal outline; low convex profile; surface smooth; transition to the nepioconch well marked.

Remarks. Pseudomalletia pianii Van Aartsen & Giannuzzi-Savelli, 1991 is a synonym of Yoldia obtusa Sars M., 1872 (CLEMAM 2016). The very similar Malletia johnsoni Clark, 1961 differs only in having a rounded anterior margin and a somewhat shorter posterior side; it is a deep water species that occurs between 1000 and 3000 m depth ( Oliver et al. 2016).

Occurrence. Box-corer samples BC71 (1 specimen), BC72 (4). Maximum length: 5.5 mm.

Distribution and habitat. Malletia obtusa ranges from the northern Atlantic—also entering Norway fjordsto North American coasts, Cape Verde and the western Mediterranean, in the 20–3200 m depth interval ( Verrill & Bush 1898; Nordsieck 1969; Di Geronimo & Panetta 1973; Poppe & Goto 1993; Buhl-Mortensen & Høisaeter 1993; La Perna 2003).

Fossil record. Pleistocene of the Mediterranean ( La Perna 2003).

Figures

FIGURE 2. a – b: Nucula sulcata Bronn, 1831; RV, sample BC 06, scale bar: 5 mm; c – e: Ennucula aegeensis (Forbes, 1844); RV (c, e) and LV (d), sample BC 72, scale bars: 1 mm (c – d), 0.1 mm (e, prodissoconch); f – h: Ledella messanensis (Jeffreys, 1870); LV, sample BC 72, scale bars: 1 mm (f – g), 0.1 mm (h, prodissoconch); i – k: Malletia obtusa (Sars M. in Sars G. O., 1872); RV (j, k) and LV (i), samples BC 72 (i) and BC 71 (j – k), scale bars: 2 mm (i – j), 0.1 mm (k, prodissoconch); l – n: Pristigloma minima (Seguenza, 1877); RV (m) and LV (l, n), sample BC 72, scale bars: 0.5 mm (l – m), 0.1 mm (n, prodissoconch); o – q: Yoldiella lucida (Lovén, 1846); RV, sample BC 72, scale bars: 1 mm (o – p), 0.1 mm (q, prodissoconch).