Before the Great Dying - Otoliths in Situ in Kupferschiefer Fishes (Lower Zechstein, Upper Permian)

The fishes from the Kupferschiefer (Zechstein, Upper Permian) of Germany are known for their exquisite preservation and they represent a window into fish life shortly before Earth’s most severe mass-extinction at the Permian–Triassic boundary where more than 90% of the marine life became extinct. Otoliths have been recorded in situ in the common Palaeoniscum freieslebeni but they have never been studied in detail. Here we describe otoliths in situ and as isolated finds of several early actinopterygians from the German Kupferschiefer as well as from the earliest neopterygian, Acentrophorus glaphyrus, and the coelacanthid Coelacanthus granulatus. We find that early actinopterygian otoliths shared a common morphological pattern characterized by a subtriangular outline and no clearly defined sulcus distinct from the otoliths of modern bony fishes. Furthermore, we are able to partly resolve the taxonomic identity of the collective early actinopterygian otolith form genus Archaeotolithus. Acentrophorus glaphyrus represents a completely different otolith morphology that shows certain resemblance to otoliths of the Halecomorphi. The morphological genesis of fish otoliths is discussed in the context of their evolution from the earliest finds in the Devonian to living taxa.