The Bony Fish Fossils of the Western Limfjord – Evolution and Climate Adaptation in the Earliest Eocene

In the western Limfjord of northern Jutland, Denmark, the coastal cliffs of Hanklit and of Knudeklint on the island of Fur expose rocks laid down about 56 to 54.6 million years ago. At the base is the Stolleklint Clay; above it lies the Fur Formation, a diatom-rich marine sediment interleaved with many layers of volcanic ash, known in Danish as moler, or mo-clay.

The beds date from only about ten million years after the end-Cretaceous extinction of the dinosaurs and ammonites, and span the Paleocene-Eocene Thermal Maximum and the cooling that followed. Their bony fishes, more than 80 species from 25 to 29 orders, make this the oldest and most important site for the early evolution of modern teleosts. Sea turtles, insects and plants are preserved in fine detail, and more than 30 bird species form the earliest diverse Paleogene bird fauna known.

The fossils are kept at the museum on Mors, at the Fur Museum, opened in 1953, and at the Natural History Museum of Denmark in Copenhagen. Mo-clay has long been dug in the region, but no commercial extraction is possible inside the property. It was inscribed in 2026 at the 48th session of the World Heritage Committee in Busan.