Cylichna stevniensis, Hansen, 2019

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 166

publication ID

https://doi.org/ 10.11646/zootaxa.4654.1.1

publication LSID

lsid:zoobank.org:pub:CFD82CC0-3110-472E-972B-7ADC0C523A04

DOI

https://doi.org/10.5281/zenodo.5583001

persistent identifier

https://treatment.plazi.org/id/75C19A0D-E889-407D-B920-71856F9E151A

taxon LSID

lsid:zoobank.org:act:75C19A0D-E889-407D-B920-71856F9E151A

treatment provided by

Plazi

scientific name

Cylichna stevniensis
status

sp. nov.

Cylichna stevniensis n. sp.

Figs 35 View FIGURE 35 Q–T

Diagnosis. Shell rather elongate with pointed posterior end, aperture distinctly higher than aperturally strongly convex penultimate whorl; apex hidden on adult specimens, not sharply truncated. Columellar fold very weak. Surface sculpture of fine spiral grooves.

Derivation of name. Refers to the type locality Stevns Klint.

Type material. Holotype MGUH 33317 View Materials is a nearly complete external mould . Paratype MGUH 33318 View Materials is an internal mould and comes from the Cerithium Limestone Member at Skeldervig . Paratype MGUH 33319 View Materials comes from the same horizon and locality as the holotype .

Additional material. Six specimens with the informal sample numbers SH.179, SH.192.B, SR.608 (2 specimens), SR.680 and SO.191, together with three uncatalogued external and internal moulds from Stevns and a single mould from Northern Jutland, which is found in the private collection of K. I. Schnetler. The Stevns material belongs to the Natural History Museum of Denmark.

Type stratum and type locality. Cerithium Limestone Member of the Rødvig Formation at Rødvig, Stevns Klint.

Occurrence. The Cerithium Limestone Member at Stevns Klint and the stratigrapically equivalent ‘dead layer’ in Dania Quarry, Northern Jutland.

Description. Protoconch unknown. Teleoconch moderately thick-shelled, involute, elongated in shape with weakly curved outer lip and aperturally strongly convex penultimate whorl; apex covered by last whorl on adult specimens. Aperture apically pointed, widened and rounded abapically. Width of last whorl, excluding aperture, corresponding to half the spire height. Columella with very weak plait partly hidden by callus.

Sculpture, if present, consisting of weak, fine spiral grooves without pitting, grooves numbering round 30 on holotype MGUH 33317.

Measurements. Largest specimen MGUH 33319 is 5.2 mm high and at least 2.8 mm wide.

Remarks. As noted by Kaim & Beisel (2005: p. 61) the species of Cylichna are extremely similar and only few features may be used for differentiation on fossil specimens. Among the stratigraphically and geographically comparable taxa Cylichna stevniensis n. sp. is distinguished from the Danian Roxania raristriata ( Briart & Cornet, 1887) from Belgium as figured by Glibert (1973: pl. XI: 1) by the distinctly higher aperture opening relative to the apex. It resembles somewhat Cylichna sp. 1 of Kollmann & Peel (1983) from the Danian of Greenland, but the columella is generally longer with a slightly better developed columellar plait.

MGUH

Museum Geologicum Universitatis Hafniensis

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

Order

Cephalaspidea

Family

Cylichnidae

Genus

Cylichna

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