Tornus subcarinatus ( Montagu, 1803 )

Tornus subcarinatus ( Montagu, 1803) View in CoL ( Fig. 9F View FIG 1-F View FIG 3 View FIG )

Helix subcarinata Montagu, 1803: 438 View in CoL , pl. 7, fig. 9.

Tornus subcarinatus View in CoL – Van Dingenen et al. 2016: 149, pl. 11, fig. 9, pl. 12, fig. 3. — Landau et al. 2018: 303, pl. 131, fig. 1.

For more, see synonymy list in Van Dingenen et al. (2016) and Landau et al. (2018).

MATERIAL AND DIMENSIONS. — Maximum height 0.8 mm, width 1.2 mm. — RGM.1364994 (19), leg. ACJ ; RGM.1365009 (93), leg. AWJ ; RGM.1365299 (1), leg. AWJ ; RGM.1405531 (1), leg. ACJ .

SPECIES CHARACTERISATION. — Small, depressed, subcircular shell. Protoconch of 2.5 smooth whorls; three teleoconch whorls with carinate shoulder, mid-whorl and peribasal cords, sinuous ribs on dorsum and venter; base flattened, bearing two further elevated cords, the medial periumbilical cord delimiting wide, deep umbilicus with ribs extending within; aperture wide, rounded, strongly oblique in profile.

DISTRIBUTION. — Middle Miocene: Atlantic, Loire Basin, France ( Glibert 1949). — Upper Miocene: Atlantic, NW France ( Landau et al. 2018). — Lower Pliocene: NSB, Coralline Crag, England ( Wood 1848; Harmer 1923; Atlantic, NW France ( Van Dingenen et al. 2016); central Mediterranean, Italy ( Chirli 2006). — Upper Pliocene: NSB, Red Crag, England ( Wood 1848; Harmer 1923). — Upper Pliocene-Pleistocene: Atlantic, NW France (Cossmann 1918; Brébion 1964). — Lower Pleistocene: Atlantic, Selsoif, NW France (this paper). — Upper Pleistocene: NSB, The Netherlands (Van Regteren Altena et al. 1954); Atlantic, British Isles (Harmer 1923). Today this species is present in the Atlantic coasts of Europe from British Isles to Tarifa ( Fretter & Graham 1978).

REMARK

Van Dingenen et al. (2016:149) highlighted the problem with the Tornus subcarinatus ( Montagu, 1803) species concept as accepted at present, in which specimens with paucispiral and multispiral protoconchs are considered conspecific. They concluded that there were two species: an Atlantic species T. subcarinatus , with a multispiral protoconch of about 2.1- 2.25 whorls, with a small nucleus (counting including first half whorl: Rolán & Rubio 2002: figs 5, 6; Van Aartsen et al. 1998: fig. 7), and a Mediterranean species that is at present unnamed with a paucispiral protoconch of 1.25-1.4 whorls, with a larger nucleus ( Rolán & Rubio 2002: figs 13, 14; Van Aartsen et al. 1998: fig. 7). With a protoconch of 2.5 whorls the specimens from Selsoif are typical of the Atlantic species T. subcarinatus .