Sveltella, Cossmann, 1889

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

Sveltella sp.

Figs 33 I–L

Material. Two fragmentary moulds, MGUH 33291 and MGUH 33292.

Occurrence. Cerithium Limestone Member at Skeldervig and Højerup, Stevns Klint.

Description. Protoconch poorly preserved, 0.85 mm high and 1.0 mm wide, low conical, consisting of between 2 and 2 ½ smooth whorls with fairly weak sutural angle.

Teleoconch slender, ranellid-like with moderately convex whorls separated by fairly deep suture. Whorls moderately low, their height corresponding to 40 % of the width. Whorl periphery located approximately 2/3 of height from adapical suture. Varix strongly developed. Aperture with straight columella carrying two strong columellar folds.

Teleoconch sculpture on initial two whorls dominated by 13 to 14 moderately sharp, strong, slightly prosocline transverse ribs, narrower than the interspaces. Number of ribs increasing with size. Transverse ribs crossed by fine spiral threads numbering 5 to 6 on spire whorls and with 12 from suture to mid-way on the base on last whorl. Growth lines sigmoid.

Measurements. Specimen MGUH 33292 is 4.4 mm high and 3.1 mm wide, consisting of protoconch and 2 ½ teleoconch whorls, the last whorl lacking base and canal.

Remarks. The taxon resembles Sveltella multistriata ( Ravn, 1939) from the Danish Selandian, although the whorls are less convex and the shell slightly more slender in outline. It also shows a strong affinity to the Danian Sveltella tobiasseni Schnetler & Petit, 2010 from Greenland, but has only up to 2 ½ protoconch whorls and not 2 ¾; the protoconch suture is less deep and the shell more slender.

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.