We report the first cephalopod statoliths from the Early Cretaceous. These unique microfossils fill the gap in the fossil record between Jurassic and Cenozoic forms, and are more similar to the former. We compare the morphology of the Mesozoic forms with the statoliths from Recent and Cenozoic decabrachians. This comparison shows the closest resemblance to the Recent Idiosepiidae. We suggest that Mesozoic cephalopod statoliths belong to the basal decabrachians and they are related to the idiosepiids. The belemnitid identity of these forms can be neither confirmed nor rejected though some positive correlation in the investigated materials between findings of belemnitid rostra and statoliths do occur. These finds support also some previous suggestions that decabrachians and vampyropods diverged earlier than in the Early Jurassic. We discuss the absence of the wing in the Mesozoic statoliths and suggest that the robustly developed spur could play a similar role to the wing in Cenozoic and Recent decabrachian statoliths. We suggest that the statolith morphology might be a useful tool to interpret cephalopod evolution. We also note an evident shift in the abundance ratio of statoliths vs fish otoliths, the former being dominant in the Jurassic while declining in abundance in the Cretaceous. This supports a Cretaceous turnover in several groups of marine organisms.
We report a Valanginian (Early Cretaceous) otolith-based ichthyofauna from a section at Wawał 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 Wawał 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 Wawał 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 Wawał 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.http://zoobank.org/urn:lsid:zoobank.org:pub:19BCD353-1CCF-4134-80D5-EDEEABA8610B
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