Opalia, H.Adams & A.Adams, 1853

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 127-128

publication ID

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

publication LSID

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

persistent identifier

https://treatment.plazi.org/id/BF18F633-A97E-FF9A-2B9C-C7ACFACBFDDC

treatment provided by

Plazi

scientific name

Opalia
status

 

Opalia View in CoL sp.

Figs 29 View FIGURE 29 L–N

Material. MGUH 33234 and MGUH 33235, both external and internal moulds.

Occurrence. The lower Danian Cerithium Limestone Member at Stevns Klint.

Description. Protoconch high conical, approximately 0.4 mm high and 0.3 mm wide, consisting of around 2 ½ moderately convex whorls. Embryonic whorl small, smooth or granulate. Larval whorls 1 ½ to two in number, carrying around 30 opisthocline collabral threads per whorl.

Teleoconch moderately slender with highly convex whorls separated by very deep suture. Whorl width nearly twice as large as height. Transition to flattened base marked by basal carina. Base smooth but for weak and wide spiral furrows. No umbilicus present. Aperture rounded ovoid with weakly concave columella.

Teleoconch sculpture dominated by around 14 sharp-ridged transverse ribs per whorl; ribs crossed by five or six weaker spiral ribs or threads, the abapical four much stronger than adapical ones.

Measurements. Specimen MGUH 33234 is 3.6 mm high and 1.25 mm wide, consisting of protoconch and 5 ¾ teleoconch whorls.

Remarks. Opalia sp. differs from the early Palaeocene Cerithiscala sp. of Kollmann & Peel (1983) from Greenland by the higher number of spiral threads. Likewise it is easily distinguished from the middle Danian Opalia tricincta ( Ravn, 1933) from Denmark, by the finer sculpture, the more slender outline and the more convex whorls. It differs from the Selandian Opalia poulseni ( Ravn, 1939) from Denmark by the finer sculpture and broader outline, and from the Selandian Opalia hauniensis ( Ravn, 1939) , also from Denmark, by the stronger spiral sculpture.

MGUH

Museum Geologicum Universitatis Hafniensis

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

Family

Epitoniidae

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