Radiolarian extinction event in the Middle Paleozoic

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Radiolarian faunal transition and geochemistry of Upper Silurian to Middle Devonian siliceous rocks in Japan and Mongolia were investigated to understand a possible mass extinction event in Early Devonian time. The result of the present study indicates the following faunal transition process: (1) the decline and subsequent extinction of Inaniguttidae occurred in the middle Early Devonian, (2) Palaeoscenidiidae that is a typical opportunistic group occupied a late Early Devonian radiolarian fauna, and (3) subsequent diversification of Entactiniidae became pronounced in the Middle Devonian. Based on the results of geochemical analysis of chert, there is a possibility that this extinction event has a causal relationship with Early Devonian environmental change attributed to a large igneous activity.