Columbellaria tuberculosa (Binkhorst, 1861)

Figs 26 L–M

1861 Pyrula tuberculosa Binkhorst: 8, pl. III, fig. 5a–b.

1861 Pyrula? plicata —Binkhorst: 68, pl. Va.3, fig. Aa–b.

1898 Columbellaria tuberculosa (Binkhorst) —Kaunhowen: 79–80, pl. IX, figs 7–8.

1986 Columbellaria tuberculosa (Binkhorst, 1861) —Abdel-Gawad: 111, pl. 13, figs 2–4.

Diagnosis. Low-spired and bulbous with unkeeled whorls. Sculpture of nearly smooth and sharp spiral ribs. Transverse ribs completely lacking.

Material. The present Danish material consists of specimen ØSM.10042-202-a–c and an uncatalogued external and internal apical mould from Holtug quarry (A. Rosenkrantz, 1—6/8 1940), which is deposited in the old collections at the Natural History Museum of Denmark.

Type stratum and type locality. The holotype figured by Binkhorst (1861: pl. III: 5a–b) comes from the upper Maastrichtian limestone at Limburg, Belgium.

Occurrence. In Denmark Columbellaria tuberculosa is found in the lithified top of the Maastrichtian Højerup Member at Rødvig and Holtug Quarry, Stevns Klint. Outside Denmark it is known from the Early Senonian of West Germany, the late Senonian of the Polish Lvov region and the Maastrichtian of Limburg (Belgium), Kunrade (Holland) and Middle Vistula Valley of Poland (Abdel-Gawad 1986).

Description of Danish material. Protoconch with three smooth and moderately convex, slowly expanding whorls. Initial two whorls nearly planispiral. Protoconch (of ØSM.10042-202-b) 1.55 mm in width and about 0.8 mm in height.

Teleoconch low-spired with moderately convex spire whorls. Shell width corresponding to 80 % of the height. Last whorl bulbous, constituting approximately 90 % of the shell height. Base evenly rounded. Aperture narrowly elongated, height corresponding to around 70 % of shell height. Inner lip only partly preserved, wide, with at least six teeth.

Teleoconch sculpture consisting of seven narrow and sharp spiral ribs of nearly equal strength on spire whorls. Last whorl with at least 16 near equal spiral ribs and more or less completely lacking tuberculation throughout. Growth lines nearly orthogonal to slightly opisthocline.

Measurements. Specimen ØSM.10042-202 is a largely complete shell measuring about 5.9 mm in height and 5.2 mm in width.

Remarks. The rare occurrence in the Danish deposits strongly suggests that Columbariella tuberculosa (Binkhorst, 1861) did not belong in this deep water muddy environment, but rather to a more shallow water firm-ground environment like that found in Holland, Belgium and Poland.