Early Cretaceous radiation of teleosts recorded by the otolith-based ichthyofauna from the Valanginian of Wąwał, central Poland

ABSTRACT

We report a Valanginian (Early Cretaceous) otolith-based ichthyofauna from a section at Wąwał in central Poland. We describe one new genus (Palaeoargentina gen. nov.), six new otolith-based species (Pteralbula polonica sp. nov., Protalbula pentangularis sp. nov., Kokenichthys kuteki sp. nov., Protoelops gracilis sp. nov., Palaeoargentina plicata sp. nov., Archaeotolithus aptychoides sp. nov.) from Wąwał and compare them to species known from similar assemblages elsewhere. The comparison of teleost diversity shows similarity to the Aptian (late Early Cretaceous) and less distinctly to the Maastrichtian (latest Cretaceous) assemblages, rather than to its coeval equivalents from Germany and southern England, and indicates that a considerable teleost diversity already existed before the mid-Cretaceous. The vertical succession of otolith taxa in the Wąwał section is in concordance to the pattern already revealed from the succession of bivalves and other benthic invertebrates and it is attributed to sea level and temperature variations. Previously identified causes of benthic invertebrate succession in the Wąwał section are used to infer paleoenvironmental factors governing fish distribution in the Valanginian marine environment recorded at this site. The new findings suggest that the radiation of teleosts started before the Valanginian, and it was a relatively long and apparently gradual process. This fossil association also reveals a significant shift in the abundance ratio of fish otoliths vs. cephalopod statoliths in fully marine deposits, with otoliths much more abundant than the statoliths in Valanginian and younger sediments while it is otherwise in the Jurassic deposits.

ACKNOWLEDGMENTS

We thank reviewers G. Stringer (University of Louisiana, Monroe, U.S.A.) and W. Schwarzhans (University of Copenhagen, Copenhagen, Denmark) for helpful comments. The study was supported by a grant from the National Science Centre of Poland (No. 2019/35/N/ ST10/04160) titled “Paleoecology, paleogeography, bathymetric distribution, and diversification pattern of fishes and cephalopods in Mesozoic epicontinental seas based on otoliths and statoliths.” SEM photos for this work were done in the Laboratory of SEM Microphotography, Institute of Paleobiology PAS, Warsaw, Poland.

AUTHOR CONTRIBUTIONS

MP designed the project, analysed data, and drafted the manuscript. KH supervised the project. AK performed fieldwork and collected materials, conceived and supervised the project. All authors edited the manuscript.