Tatara, Fleming, 1950

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 153-155

Tatara sp.

Figs 33 F–H

Material. A single external and internal mould, MGUH 33290.

Occurrence. The lower Danian Cerithium Limestone Member at Skeldervig, Stevns Klint.

Description. Protoconch poorly preserved, obtusely conical with at least two smooth and rather weakly convex whorls. Height at least 0.6 mm.

Teleoconch slender, mitriform with moderately to weakly convex whorls separated by thin, shallow suture mainly marked by whorl angle. Whorl width corresponding to 1.6 times the height. Last whorl moderately convex with a rather gradual transition to canal. Aperture narrowly lenticular with a height corresponding to slightly over half the shell height. Columella fairly long with two strong columellar folds on adapical half, succeeded abapically by at least four blunt teeth. Callus absent or thin, exposing continuation of spiral sculpture on parietal region. Outer lip thickened into varix with 11 evenly spaced teeth on inner side; teeth strongest on adapical part.

Teleoconch sculpture reticulate, consisting of sharp-ridged and weakly prosocline transverse ribs crossed by spiral ribs. Tubercles formed at connecting nodes. Third teleoconch whorl with 4–5 primary spiral ribs and around 28 to 30 transverse ribs. Varices occur with a frequency of nearly 2/3 per whorl.

Measurements. MGUH 33290 is 19.8 mm high and around 10.5 mm wide, consisting of about five teleoconch whorls and the lower two protoconch whorls.

Remarks. Tatara sp. differs from T. pseudosassia n. sp. described above by the slender outline and a finer transverse teleoconch sculpture. It seems furthermore to differ from the Danish middle Danian T. danica Schnetler & Petit, 2006 by the presence of more teeth on the outer lip, by the slender form and by the gradual transition from base to canal on the last whorl.

Figures

FIGURE 33. A. Mangeliid genus et sp. indet., Silicone cast of MGUH 33286. Protoconch width 0.8 mm. B–E. Tatara pseudosassia n. sp. B–C. Silicone cast of holotype MGUH 33287. Width 4.8 mm. D. Silicone cast of paratype MGUH 33288. Width 3.7 mm. E. Internal mould of last whorl of paratype MGUH 33289. Width 5.9 mm. F–H. Tatara sp., Silicone cast and internal moulds of MGUH 33290. Widths 10.4, 9.9 and 9.9 mm respectively. I–L. Sveltella sp. I–J. Silicone cast of MGUH 33291. Width of teleoconch 3.0 mm. Width of picture J 3.5 mm. K–L. Silicone cast of MGUH 33292. Widths 3.1 mm. M–N. Babylonella sp. M. Silicone cast of MGUH 33293. Width 1.6 mm. Picture by S.L. Jakobsen. N. Silicone cast of MGUH 33294. Width 1.7 mm. O–R. Unitas heinbergi n. sp. O–Q. Silicone cast of holotype MGUH 33295. Widths 3.0, 3.0 (vertical on figure) and 2.8 mm respectively. R. Silicone cast of paratype MGUH 33296. Width 2.9 mm.