Retusa obtusa ( Montagu, 1803 )

Retusa obtusa ( Montagu, 1803) View in CoL

( Fig. 13D View FIG 1-D View FIG 3 View FIG )

Bulla obtusa Montagu, 1803: 223 View in CoL .

Utriculus obtusus View in CoL – Harmer 1923: 797, pl. 63, fig. 4.

Retusa alba – Van Regteren Altena et al. 1965: 26, pl. 21, fig. 205. — Ceulemans et al. 2018: 122, pl. 7, fig. 9.

For more, see synonymy list in Ceulemans et al. (2018).

MATERIAL AND DIMENSIONS. — Maximum height 1.7 mm, width 0.8 mm. — RGM.1365120 (20), leg. AWJ ; RGM.1365121 (1), leg. AWJ ; RGM.1365017 (3), leg. ACJ .

SPECIES CHARACTERISATION. — Shell small, subcylindrical with low spire. Two to three teleoconch whorls separated by deeply impressed suture. Surface smooth. Aperture elongate expanded abapically.

DISTRIBUTION. — Lower Pliocene: NSB, England (Harmer 1923); Atlantic, NW France ( Ceulemans et al. 2018). — Upper Pliocene: NSB, Red Crag, England ( Wood 1848). — Upper Pliocene-Pleistocene: NSB, Holland (Van Regetren Altena et al. 1955). — Lower Pleistocene: Atlantic, Selsoif, NW France (this paper). — Middle Pleistocene: Atlantic, Irish Sea (Harmer 1923). Today, this species occurs in the Atlantic from Greenland, Iceland to Scandinavia, Nova Scotia to Aleutian Islands, British Isles ( Thompson 1988).

REMARKS

Retusa obtusa is variable in shape and size with a more or less elevated apex ( Ceulemans et al. 2018). As noted by those authors, this species is rarely reported in the fossil literature. It is predominantly a cooler water species with the most southern record being that of the Lower Pliocene of Le Pigeon Blanc (NW France).