Cerithiopsis rosenkrantzi (Ravn, 1933) Hansen, 2019

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 149-150

Epalxis ? rosenkrantzi n. sp.

Figs 32 H–K

Diagnosis. Protoconch with two and a half whorls. Teleoconch relatively low, compact, with strongly carinated whorls with distinctly concave shoulder slope. Transverse ribs not overly falcate in form. Growth lines with rather wide and shallow sinus.

Derivation of name. In honour of A. Rosenkrantz, who collected the type material and worked on the gastropod faunas from the Palaeogene of Denmark and Greenland.

Type material. The holotype, MGUH 33279 , is a nearly complete external mould collected by A. Rosenkrantz on 25 July 1943 . Paratype MGUH 33280 was collected from the Cerithium Limestone Member at Skeldervig, Stevns Klint .

Additional material. Two external moulds have been examined from the uncatalogued old collections of the Natural History Museum of Denmark. Both are collected by A. Rosenkrantz at Skeldervig (18 October 1943) and between Knøsen and Harvig (25 July 1943) at Stevns.

Type stratum and type locality. Cerithium Limestone Member from somewhere between Knøsen and the first ladder at Harvig, Stevns Klint.

Occurrence. Rather rare in the Cerithium Limestone Member at Skeldervig and south of Knøsen, Stevns Klint.

Description. Protoconch 0.65 mm high and 0.7 mm wide, conical, consisting of 2 ½ smooth, weakly convex whorls separated by shallow suture. Transition to teleoconch fairly sharp, marked by the appearance of transverse nodes. Teleoconch shell small, compact and moderately thick with low carinated whorls two and a half times as wide as high. Shoulder carina pronounced, located approximately 1/3 of whorl height from abapical suture; shoul- der slope wide, convex, delineated by slight spiral swelling adjacent to adapical suture. Aperture elongated with rather gradual transition to wide, oblique siphonal canal, combined height corresponding to 3/5 of shell height. Lips smooth. Columella concave, abaxially deflected to the left.

Teleoconch sculpture dominated by around 11 short transverse ribs or nodes per whorl; ribs sometimes developed into short spike where crossed by shoulder carina, fading out on abapical half of smooth shoulder slope and on adapical part of base. Transverse rib may form weak node on subsutural swelling. Spiral threads weak, strongest on base, fading out at periphery. Growth lines describing moderately weak and widely open, V-shaped sinus with apex at shoulder.

Measurements. Largest specimen, holotype MGUH 33279 is 6.0 mm high and 2.7 mm wide, consisting of protoconch and three teleoconch whorls.

Remarks. The generic assignment is tentative due to the rather open sinus and the resulting weakly developed falcate shape of the transverse ribs.

Figures

FIGURE 32. A. Ptychatractidae genus et sp. indet. Silicone cast of MGUH 33274. Width 1.8 mm. B–G. Orthosurcula s.l. cerithiorum (Ravn, 1902). B. Silicone cast of lectotype MGUH 123. Height 11.4 mm. Photograph by S. L. Jakobsen. C. Silicone cast of MGUH 33275. Height 4.8 mm. D. Silicone cast of MGUH 33276. Height 13.7 mm. E. Silicone cast of MGUH 33277. Width 6.4 mm. F. Silicone cast of MGUH 119, holotype of Pleurotoma steenstrupii Ravn, 1902. Height 23.6 mm. G. Silicone cast of MGUH 33278. Height 2.4 mm. H–K. Epalxis? rosenkrantzi n. sp. H–J. Silicone cast of holotype MGUH 33279. Widths 2.7, 2.8 and 2.8 mm respectively. K. Silicone cast of paratype MGUH 33280. Width 2.5 mm. L–N. Pseudocochlespira transversa n. sp. L–M. Silicone cast of holotype MGUH 33281. Widths 5.9 and 6.0 mm respectively. N. Silicone cast of paratype MGUH 33282. Width 8.2 mm. O–S. Pseudotoma danica n. sp. O–P. Silicone cast of holotype MGUH 33283. Width 5.7 mm. Q. Silicone cast of paratype MGUH 33284. Width 7.0 mm. R. Silicone cast of paratype MGUH 33285. Width 6.3 mm. S. Silicone cast of ØSM.10042-272-b. Width 5.8 mm. T–U. Mangeliid genus et sp. indet., Silicone cast of MGUH 33286. Widths 3.3 and 4.8 mm respectively.