Clathrobaculus, Cossmann, 1912

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 164-165

Clathrobaculus sp.

Figs 35 J–K

Material. MGUH 33313 and an external mould with the informal sample number SR.938, collected in connection with this study.

Occurrence. Upper 15 centimetres of the upper Maastrichtian Højerup Member at Rødvig, Stevns Klint.

Description. Protoconch smooth, apparently hyperstrophic, but only last quarter of a whorl preserved. Transition to teleoconch sharp.

Teleoconch thick-shelled, very slender with relatively high, convex, keeled whorls; keel located just abapical to whorl center; whorl height corresponding to approximately 80 % of the width. Suture very faint.

First teleoconch whorl with three spiral ribs, a weak adapical one and two stronger spiral ribs located on keel and halfway between keel and abapical suture. A fourth, weak spiral rib is added between spiral rib 1 and keel on second teleoconch whorl. Spiral ribs crossed by faint transverse, largely orthocline transverse ribs numbering around 20 per half whorl on the fourth teleoconch whorl.

Measurements. MGUH 33313 is 1.8 mm high and 0.5 mm wide, consisting of part of the protoconch and the first 5 ½ teleoconch whorls.

Remarks. Clathrobaculus sp. is the youngest taxon so far, which with any degree of confidence may be assigned to this genus (see Kaim 2004: p. 140). There are, though, two taxa from the slightly younger middle Danian deposits of Denmark that may belong here, but at present their protoconchs are unknown ( Lauridsen & Schnetler 2014: pp. 109–110).

The Danish specimen strongly resembles the Early Cretaceous Clathrobaculus sp. 1 sensu Kaim (2004) from Poland, but differs by the higher number of transverse ribs, which appear weaker and by the later appearance of spiral rib 2.

Figures

FIGURE 35. A–B. Pseudomalaxis sp., Silicone cast of MGUH 33306. Width 4.3 mm. C–D. Climacopoma? sp., Silicone cast of MGUH 33307. Width 13.1 and 9.9 mm respectively. E–I. Mathilda dania n. sp. E. Silicone cast of holotype MGUH 33308. Width 1.9 mm. F. Silicone cast of paratype MGUH 33309. Width 2.0 mm. G. Silicone cast of paratype MGUH 33310. Width 0.8 mm. H. Silicone cast of paratype MGUH 33311. Width 0.7 mm. I. Silicone cast of paratype MGUH 33312. Width 1.7 mm. J–K. Clathrobaculus sp., Silicone cast of MGUH 33313. Width 0.5 mm. L–P. Ringicula sp. L. Silicone cast of MGUH 33314. Width 7.0 mm. M–N. Silicone cast of MGUH 33315 and a partly hidden second specimen. Width 7.3 and 6.6 mm respectively. O–P. Silicone cast of MGUH 33316. Width 5.6, 5.3 mm respectively. Q–T. Cylichna stevniensis n. sp. Q. Silicone cast of holotype MGUH 33317. Width 1.4 mm. R–S. Internal mould of paratype MGUH 33318. Width 1.5 mm. T. Internal mould of paratype MGUH 33319. Width 2.8 mm. U–V. Cylichna? sp. A. Cast of MGUH 33320. Width 2.3, 2.4 mm respectively. W–Y. Cylichna? sp. B. W. Wax cast of MGUH 33321. Width 2.4 mm. X–Y. Inner mould of MGUH 33322. Width 1.3 mm. Z–AE. Roxania sp. Cast of MGUH 33323. Width 3.2, 3.3 mm respectively.