A Devonian phoebodont shark tooth from a Lower Cretaceous karst fill

摘要

The Sauerland mountain ridge in NW Germany is well known for its high number of caves and fissures, which are developed within Devonian reef limestones. Several karst events took place in geological history and the resulting cavities were often refilled by sediment. One of these karst fissures near Balve in the Remscheid-Altena Anticline contains sediments of Barremian to Aptian age with fossil remains of fish, turtles, crocodiles, pterosaurs, dinosaurs, and mammals. Among them, a single, extraordinarily preserved, minuscule shark tooth is indistinguishable in its preservation from the Cretaceous fossils. Nevertheless, several characters, such as an orolingual button on the surface of its base clearly identify it as the tooth of Phoebodus sophiae, an ancient shark taxon approximately 255 million years older than the Cretaceous vertebrate remains in the karst fissure. It is the first unambiguous evidence of the Phoebodus type species in Germany.