Bodil W. Lauridsen and K.I. Schnetler
Fossiliferous middle Danian limestones of the Faxe Formation, exposed in a large quarry on the Stevns peninsula, eastern Denmark, yield a detailed record of the complex ecosystem associated with cold-water coral mounds. A particular sedimentary–diagenetic facies, the Baunekule facies, preserves the faunal record in exceptional detail.
This bulletin presents a catalogue of the gastropod fauna from the Baunekule facies, providing the taxonomic status of 194 taxa; one new species (Zaclys? nuetzeli) is introduced. The catalogue is fully illustrated with a combination of detailed drawings and photographs, the former produced in the 1960s by Erna Nordmann, Gunni Jørgensen and Betty Engholm under the direction of Professor Alfred Rosenkrantz. The bulletin documents the high diversity of the gastropod fauna and the overwhelming dominance of small (millimetre-sized) carnivorous forms that browsed on the coral substrate. Over 80% of this unusual fauna may be endemic to the Faxe Formation, probably reflecting the specialised nature of the cold-water coral mound ecosystem.
This catalogue of 194 gastropod taxa is based on the collection of Danian gastropods from the Baunekule facies, Faxe Formation in eastern Denmark. The gastropod fauna is extremely rich and well preserved. Most of the gastropods (106 species) are referred to genus level only, 9 morphotypes to even higher taxonomical levels and 79 gastropods are referred to species level. The gastropods are classified following Bouchet & Rocroi (2005) as 4 different clades: Vetigastropoda (represented by 26 species and 10 superfamilies), Caenogastropoda (represented by 142 species and 17 superfamilies), Heterobranchia (represented by 23 species and 5 superfamilies) and Opisthobranchia (represented by 1 species and 1 superfamily). The new species Zaclys? nuetzeli n. sp. is introduced.
The Faxe Formation is recognised as a cold-water coral ecosystem with interfingering smaller bryozoan mounds. The Baunekule facies is found in the upper part of the coral mound complex of the Faxe Formation, where it forms isolated lensoidal bodies in the flanks of some of the coral mounds. It is characterised by a high diversity invertebrate fauna that occurs in weakly consolidated coraldominated floatstone to rudstone. The diagenesis of the Baunekule facies is of special significance because a high proportion of the originally aragonite-shelled fauna is preserved by recrystallization to calcite during early burial diagenesis. Most of the gastropods are not known from other parts of the Faxe Fm. The fauna is very important for comparative evolutionary studies of fossil and modern gastropods on cold-water coral mounds. Many of the genera have not previously been recorded from Danian strata. None of the gastropod species found in the Baunekule facies are known for certain to range below the Cretaceous–Palaeogene boundary. The fauna is comparable to gastropods found on modern cold-water coral mounds in the North Atlantic.
The gastropod fauna from the Baunekule facies is characterised by a very high diversity of rather small millimetre-sized gastropods with a preference for hard substrates; 63.9% of the taxa belong to the browsing carnivore trophic group, feeding mainly on sedentary animals. Surprisingly, the fauna contains some common occurrences of typically warm-water species. The fauna consists mostly of Cenozoic genera and up to 87% of the species may be endemic to the cold-water coral ecosystem of the Faxe Formation. The diverse and rather unusual gastropod fauna from the Baunekule facies is undoubtedly linked to the evolution of cold-water coral ecosystems.
B.W.L., Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350 København K. E-mail: firstname.lastname@example.org
K.I.S., Fuglebakken 14, Stevnstrup, 8870 Langå
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