Cerithiella, Hansen, 2019

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 120

Cerithiella sp.

Figs 28 P–Q

2014 Cerithiella sp. Hansen & Surlyk: 339, fig. 6: 4, tab. 3.

Material. MGUH 33216, MGUH 33217 and three fragmentary external moulds of teleoconchs with the informal sample numbers SR.739, SR.777 and SR.912.B–C.

Occurrence. Lithified top of the Maastrichtian Tor Formation at Rødvig and Holtug Quarry, Stevns Klint.

Description. Teleoconch slender with a slightly stepped outline due to deeply impressed and broad suture. Whorls strongly flattened, rounded subrectangular in outline with a height corresponding to 2/5 the width; peripheral keel located just above abapical suture succeeded by weak abapical keel covered by adapical wall of succeeding whorl. Base weakly convex. Columella strong and relatively short with no or only very weakly developed columellar fold. Aperture not preserved.

Teleoconch sculpture composed of strong reticulate pattern of up to around 30 sharp and slightly prosocyrt transverse ribs crossed by four equally strong spiral ribs adapically to base. Strongest spiral rib located on keel. Transverse ribs terminating at sutures. Small tubercles present at connecting points between ribs. Base with one primary spiral rib located on abapical keel and succeeded by increasingly weaker spiral ribs axially. Growth lines fine, their course corresponding to that of the transverse ribs.

Measurements. Largest specimen, MGUH 33216, consisting of 5 ½ teleoconch whorls is 13 mm high and 6.7 mm wide.

Remarks. The taxon strongly resembles C. moltkianum ( Ravn, 1902) , but differs by the staircase outline and the more pronounced reticulation with four instead of three spiral ribs on each whorl.

Figures

FIGURE 28. A. Thereitis carlsbergi n. sp., Protoconch of paratype MGUH 33205.Width of protoconch 0.4 mm. B–D. Thereitis cretacea n. sp. B. Holotype protoconch MGUH 33206. Width 0.4 mm. C. Silicone cast of paratype MGUH 33207. Width 0.9 mm. D. Silicone cast of paratype MGUH 33208. Width 1.1 mm. E. Thereitis sp., Silicone cast of MGUH 33209. Width 0.4 mm. F–I. Cerithiella moltkianum (Ravn, 1902). F–H. Silicone cast of MGUH 33210. Width of teleoconch 4.6 mm. Height of protoconch 1.0 mm. I. Silicone cast of MGUH 33211.Width 9.2 mm. J–O. Cerithiella selandica n. sp. J–K. Silicone cast of holotype MGUH 33212. Teleoconch width 2.6 mm. Preserved protoconch width 0.5 mm. L–M. Silicone cast of paratype MGUH 33213. Height 31 mm. N. Paratype protoconch MGUH 33214. Width 0.7 mm. O. Silicone cast of paratype MGUH 33215. Width 2.6 mm. P–Q. Cerithiella sp. P. Silicone cast of MGUH 33216. Width 6.7 mm. Q. Silicone cast of MGUH 33217. Width 5.1 mm. R. Eumetula sp., Silicone cast of MGUH 33218. Width 0.9 mm. S. Trituba obliquecostulata (Kaunhowen, 1898). Silicone cast of MGUH 33219. Width 1.2 mm. T–V. Vatopsis heinbergi n. sp. T. Silicone cast of holotype MGUH 33220. Width 1.2 mm. U. Silicone cast of paratype MGUH 33221. Width 3.1 mm. V. Silicone cast of paratype MGUH 33222. Width 4.0 mm. W. Vatopsis sp., Silicone cast of MGUH 33223. Width 2.5 mm. X–Y. Ageria skeldervigensis n. sp. X. Silicone cast of paratype MGUH 33224. Height 4.1 mm. Y. Silicone cast of paratype MGUH 33225. Width 7.4 mm.