Tricolia pullus picta ( da Costa, 1778 )

Tricolia pullus picta ( da Costa, 1778) View in CoL

( Fig. 5D View FIG 1-D View FIG 3 View FIG )

Turbo pictus da Costa, 1778: 103, pl. 8, figs 1, 3.

Tricolia pullus View in CoL s.l. – Landau et al. 2017: 153, pl. 77, figs 1-6.

For more, see synonymy list in Landau et al. (2017).

MATERIAL AND DIMENSIONS. — Height 2.3 mm (incomplete), width 2.0 mm. — RGM.1365082 (1), leg. AWJ .

SPECIES CHARACTERISATION. — Shell turbiniform, only last whorl showing a flattened profile to the upper half, rounded periphery, bearing reddish zigzag colour pattern interrupted by two rows of white blotches the upper placed below the suture, the lower mid-whorl.

DISTRIBUTION (OF SUBSPECIES T. pullus picta ). — Upper Pliocene: Atlantic, St Erth, England (Harmer 1925), Selsoif, NW France (this paper). Today it is present from the western coasts of British Isles (absent in Scandinavia and North Sea) south to Gibraltar ( Fretter & Graham 1977). Further south it is replaced by the subspecies T. pullus canarica Nordsieck, 1973 in the Canary Islands & Madeira ( Hernández et al. 2011). It lives in rocky pools, 0-35 m depth, common on red weeds ( Fretter & Graham 1977).

REMARKS

Two subspecies occur today. Tricolia pullus pullus (Linnaeus, 1958) , present in the Mediterranean to the Strait of Gibraltar, is characterised by its rounded last whorl and spotted colour pattern. The Atlantic T. pullus picta ( da Costa, 1778) ranging from the British Isles to Morocco has a flattened base of the last whorl and predominantly zigzag pattern that is especially prominent on the base. The material at hand consists of a single fragment of a last whorl that agrees with the present-day Atlantic form. In their work on the Tortonian Upper Miocene of NW France, Landau et al. (2017: 153) noted that all forms occurred together in those assemblages and postulated that these subspecies may not have separated at the time. The material from Selsoif is scant, but suggest the Atlantic form had split by at least the Gelasian.