Pseudamussium peslutrae Linnaeus 1771

Pseudamussium peslutrae ? (Linnaeus, 1771)

Fig. 4 j–m

Ostrea pes lutrae Linnaeus, 1771 (p. 547).

Pecten septemradiatus Müller, 1776 (p. 248, n. 2992).

Pecten pes-lutrae Linnè—Jeffreys 1879 (p. 557).

Peplum septemradiatum (Müll.) — Sacco 1897 (p. 38, pl. 12, figs. 16–21).

Chlamys (Pseudamussium) septemradiata (Müller) — Tebble 1966 (p. 61, pl. 5, figs. a, c; pl. 6, fig. m).

Pseudamussium septemradiatum (Müller, 1776) — Nordsieck 1969 (p.48, pl. 7, fig. 31.20); Thomsen & Vorren 1986 (pl. 5, fig. B).

Pseudamussium septemradiatum (O.F. Müller, 1776) — Poppe & Goto 1993 (p. 70, pl. 10, fig. 7); Giannuzzi-Savelli et al., 2001 (p. 178, figs. 348–350).

Pseudamussium septemradiatum (Müller, O.F., 1776) — Salas 1996 (p. 55).

Pseudamussium septemradiatum (Mueller O.F., 1776) — Repetto et al. 2005 (p. 298, mid left fig).

Pseudamussium peslutrae (Linnaeus, 1771) — Oliver et al. 2016 (online resource).

Diagnostic characters. Ovate triangular, thin shell; triangular anterior auricle of the left valve with a reticulate pattern of radial ribs and concentric lamellae; five visible main radial folds and minor intermediate ones; superimposed dense radial riblets, the ones on top of the folds stronger; nepioconch with microsculpture of incremental lamellae and divergent, discontinuous fine radials in the interspaces; colour pattern of roughly concentric orange-brown bands and spots. Prodissoconch: shell type ST-2A; P-2 length about 230 µm; P-1 about 90 µm; P-2 smooth, obliquely ellipsoidal, more extended anteroventrally; P-1 convex profile; the poorly preserved surface apparently smooth; P-1/P-2 boundary well marked; transition to the nepioconch well marked, with sudden appearance of the sculpture.

Remarks. A single, broken juvenile valve is at hand, doubtfully assigned to Linnaeus’ taxon. Pseudamussium septemradiatum (Müller, 1776) is currently regarded as a synonym of the present taxon (CLEMAM 2016). Pseudamussium peslutrae differs from the very similar P. clavatum (Poli, 1795) in having a flatter and broader shell with somewhat lower radial folds.

Occurrence. Box-corer sample BC67 (1 specimen). Height: 5.5 mm.

Distribution and habitat. The species is distributed from Norway and the North Sea to West Africa; in the Mediterranean it seems to be restricted to the Alboran basin and nearby waters; it is a free living species usually found on muddy to mixed sediments between 10 and 600 m depth (Poppe & Goto 1993; Giribet & Peñas 1997; Oliver et al. 2016). Pseudamussium peslutrae is a member of the so-called “Celtic malacological fauna” (Würm or Weichselian Glacial, 13,000–9,800 YBP) that entered as a boreal guest in the Mediterranean and then apparently disappeared—except for the Alboran basin—because it does not tolerate a salinity over 36.5‰ (Emig & Geistdoerfer 2004); at present, the Mediterranean salinity ranges from about 37‰ in the Balearic basin to 39.5‰ in the Levantine basin, being around 38.5‰ in the Santa Maria di Leuca area. The species was regarded as an exclusive characteristic element of VP (bathyal mud) biocoenosis (Pérès & Picard 1964; Di Geronimo 1979[a]).

Fossil record. Plio-Pleistocene of Italy, Scandinavia and Denmark (Sacco 1897; Petersen 2004); bathyal Pleistocene (regional Würm stage) of central Italy (Di Geronimo & Bellagamba 1985).