Heteranomia squamula (Linnaeus, 1758)

Fig. 6 d–g

Anomia squamula Linnaeus, 1758 (p. 701).

Anomia aculeata Müller, 1776 (p. 249, n. 3005).

Anomia aculeata Linné [in text] Gmelin [in plate]—Dall 1889[b] (p. 32, pl. 53, figs. 5–8).

Anomia aculeata Muller—Hidalgo 1917 (p. 134).

Heteranomia squamula, L. 1758— Winckworth 1922 (p. 33, pl. 1, figs. 5–7,12).

Heteranomia squamula (Linnaeus) — Tebble 1966 (p. 37, text-figs. 4b, 18d).

Heteranomia squamula (Linné, 1758) — Nordsieck 1969 (p. 60, pl. 10, fig. 37.10); Thomsen & Vorren 1986 (pl. 4, fig. C).

Heteranomia squamula (Linnaeus, 1758) — Poppe & Goto 1993 (p. 74); Petersen 2004 (p. 72, fig. 61); Peñas et al. 2006 (p. 140, figs. 385–388); Oliver et al. 2016 (online resource).

Pododesmus aculeatus (O.F. Müller, 1776) — Poppe & Goto 1993 (p. 75, pl. 12, fig. 2).

Pododesmus (Monia) aculeatus (O.F. Müller, 1776) — Giannuzzi-Savelli et al. 2001 (p. 210, figs. 437–440).

Pododesmus (Heteranomia) squamula (Linné, 1758) — Giannuzzi-Savelli et al. 2001 (p. 212, fig. 450).

Pododesmus squamula (Linné, 1758) — Repetto et al. 2005 (p. 302, bottom right fig.).

Pododesmus aculeatus (Mueller O.F., 1776) — Repetto et al. 2005 (p. 303, top left fig.).

Pododesmus squamula — Ceregato et al. 2007 (fig. 3.5).

Diagnostic characters. Oval to subrounded, variously twisted shell; rounded byssal notch on the right valve; outer surface with either randomly arranged fluted spines or uneven growth markings only. Prodissoconch: shell type ST- 2A; P-2 length about 200 µm; roundish, weakly inequilateral outline more expanded posteroventrally; convex profile; P-1/P-2 boundary ill-defined; P-2 with commarginal cordlets towards the nepioconch; shallow sinuation on the antero-ventral margin of P-2; transition to the nepioconch well marked.

Remarks. Pododesmus aculeatus (Müller, 1776), sometimes considered a different species, is herein regarded as a synonym (Winckworth 1922; Peñas et al. 2006; CLEMAM 2016).

Occurrence. Box-corer samples BC04 (19 specimens), BC05 (20), BC10 (2), BC11 (56), BC19 (1), BC22 (17), BC41 (10), BC66 (353), BC67 (319), BC68 (19), BC70 (27), BC71 (2913), BC72 (1597); cores BC04 (6), BC05 (100), BC21 (29), BC51 (13), BC67 (61), BC72 (196). Maximum height: 9.5 mm.

Distribution and habitat. Heteranomia squamula ranges from the northern Atlantic (North America, Iceland and Norway) to western Mediterranean, from the intertidal belt to about 1000 m depth. It lives on a variety of small hard substrates including Lophelia deep-water corals, Corallium rubrum, algae and crustaceans, denoting a decrease in sedimentation rates in an upper bathyal setting (Nordsieck 1969; Poppe & Goto 1993; Pons-Moyà & Pons 1999; Crocetta & Spanu 2008; Oliver et al. 2016). In the Santa Maria di Leuca CWC biotope it was very abundantly found in framework-building coral, coral rubble and solitary coral thanatofacies (Rosso et al. 2010).

Fossil record. Miocene to Recent (Monegatti & Raffi 2001; Petersen 2004), being frequent in Pleistocene bathyal deposits of central and southern Italy (Di Geronimo & Bellagamba 1985; Di Geronimo & La Perna 1997; Di Geronimo et al. 2005); it characterizes recurring associations in the Lower and Middle Pliocene of northern Italy (Ceregato et al. 2007; Tabanelli 2008).