Cerithiopsis restemlongis, Hansen, 2019

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 112-113

Cerithiopsis restemlongis n. sp.

Figs 27 T–W

Diagnosis. Shell high and slender, more turriculate than cyrtoconoid; teleoconch whorls relatively wide with four spiral ribs of which only the 2 nd and 3 rd are tuberculated; transverse ribs strong and rounded, approximately 12 per whorl.

Derivation of name. The name, which translates ‘long rope’, refers to the slender and rope-like outline of the shell.

Type material. The holotype, MGUH 33198 is an external mould with preserved protoconch, while paratype MGUH 33199 is an external mould from the lithified top of the Tor Formation at Stevns Klint just north of Stevns Fyr and paratype MGUH 33200 is a well preserved protoconch mould from the very top of the Cerithium Limestone Member at Rødvig. Paratype MGUH 33201 is a protoconch from the Cerithium Limestone Member , 40 to 50 cm above the K-Pg boundary at Rødvig, Stevns Klint.

Additional material. Four fragmentary moulds from the informally catalogued samples SH.281.A and C, SR.406, SR.744 and SR.919, and a mould without number from north of the lighthouse Stevns Fyr. All are deposited in the collections at the Natural History Museum of Denmark.

Type stratum and type locality. Holotype MGUH 33198 is collected from the lithified interval encompassing the K-Pg Boundary at Skeldervig, Stevns Klint.

Occurrence. Top Højerup Member of the Maastrichtian Tor Formation to the top of the lower Danian Cerithium Limestone Member of the Rødvig Formation at Stevns Klint.

Description. Shell high, extremely slender, the teleoconch only widening very slightly abapically. Protoconch turriform multispiral, consisting of 5 to 5 ½ smooth and convex whorls, evenly widening down to last two whorls at which the size increase lessens. The last whorls may show very weakly developed abapical spiral lirae and around 25 to 30 indistinct opisthocline threads per whorl. Last whorl carrying one or two weakly developed spiral ribs, which continue on to the teleoconch whorls. Transition from protoconch to teleoconch rather abrupt. The teleoconch consists of up to 12 relatively low and wide whorls with the whorl height corresponding to just over 60 % of width. Teleoconch whorls flatly convex, weakly reticulate with four spiral ribs and around 12 strong and rounded transverse ribs centrally on whorl. First spiral rib weak and narrow, bordering deep suture; second rib strongest, followed by a slightly weaker third spiral rib, both well rounded and coarsely tuberculated; fourth rib fairly weak, located just above suture, on the last whorl continuing out onto sharp keel. Transverse ribs generally slightly opisthocline, but may become orthocline to weakly prosocline. Base of shell flat to slightly concave, smooth but for weak and closely spaced spiral ribs and growth lines.

Measurements. Holotype MGUH 33198, comprising 12 whorls, is 4.0 mm high and 0.9 mm wide with a 1.05 mm high and 0.4 mm wide protoconch.

Remarks. Cerithiopsis restemlongis n. sp. is distinguished from most species belonging to this genus by its very high and slender spire and the presence of only two tuberculated ribs, which are well rounded in cross-section. It resembles the Danish middle Danian Cerithiopsis cf. rosenkrantzi ( Ravn, 1933) sensu Nützel (1998) , but is distinguished by the distinctly lower whorls and seemingly slightly higher number of transverse ribs per whorl. It differs from the middle Danian Cerithiopsis rosenkrantzi ( Ravn, 1933) sensu stricto from Denmark by the presence of only two tuberculated spiral ribs and by the flatter whorls. It also appears very close to a rather poorly preserved species of Cerithiopsis from the Campanian of Spain figured by Kiel (2001), but appears to differ by a less inflated protoconch whorl and a markedly larger protoconch size. It has a strong resemblance to Zaclys ? sp. sensu Nützel (1998) from the middle Danian limestone deposits at Faxe, Denmark. It differs by having a much higher protoconch with more convex whorls and by a flatter teleoconch whorl.

Figures

FIGURE 27. A–B. Melanella? sp., Silicone cast of MGUH 33183. Width 1.4 mm. C–E. Vermetus sp., C. Silicone cast of attached tube MGUH 33184. Largest diameter 6.6 mm. D. Inner mould of protoconch and initial teleoconch inside bryozoan ball. MGUH 33185. Protoconch 0.5 mm wide. E. Silicone cast of MGUH 33186. Width 3.5 mm. F–J. Thylacodes contendis n. sp. F. Attached holotype mould MGUH 33187. Width 2.4 mm. G–H. Silicone cast of paratype MGUH 33188. Width 2.9 mm. I. Silicone cast of paratype MGUH 33189. Width 3.0 mm. J. Silicone cast of free whorl paratype MGUH 33190. Tube diameter 1.8 mm. K–M. Thylacodes? sp., Silicone cast of MGUH 33191. Width 2.4 mm. N. Dendropoma sp., Protoconch and initial teleoconch tube of MGUH 33192. Width 1.7 mm. O. Laxispira sp., Silicone cast of MGUH 33193. Width 3.6 mm. P–R. Epetrium s.l. skeldervigensis n. sp. P. Silicone cast of holotype MGUH 33194. Width 2.4 mm. Q. Silicone cast of paratype MGUH 33195. Width 4.0 mm. R. Silicone cast of paratype MGUH 33196. Width 3.6 mm. S. Triphoridae genus et sp. indet. Sinistrally coiled protoconch MGUH 33197. Width 0.7 mm. T–W. Cerithiopsis restemlongis n. sp. T. Silicone cast of holotype MGUH 33198. Width 1.0 mm. U. Silicone cast of paratype MGUH 33199. Width 1.5 mm. V. Silicone cast of paratype protoconch MGUH 33200. Width 0.5 mm. W. Silicone cast of paratype protoconch MGUH 33201. Width 0.6 mm and height 1.1 mm. X. Cerithiopsis? sp., Silicone cast of MGUH 33202. Width 0.6 mm. Y–AE. Thereitis carlsbergi n. sp. Y–Z. Silicone cast of holotype specimen MGUH 33203. Width of protoconch 0.6 mm and teleoconch 1.4 mm. AE. Silicone cast of paratype MGUH 33204. Width 0.7 mm.