Lower Triassic (Spathian) radiolarians from the Kuzu area (Tochigi Prefecture, central Japan)

A well-preserved Lower Triassic radiolarian fauna was found in a siliceous claystone and chert sequence in the Kuzu area of the Ashio Terrane, central Japan. This fauna includes "Paleozoic type" radiolarians represented by spicular type Palaeoscenidiidae and Entactiniidae with some common species of the Late Early Triassic Parentactinia nakatsugawaensis (Pn) Assemblage. Spathian conodonts Neospathodus triangularis (Bender) and Neohindeodella benderi (Kozur & Mostler) co-occur with these radiolarians. Based on the faunal analysis and chronological dating by conodonts, this radiolarian fauna probably represents an older part of the Pn Assemblage, where "Paleozoic type" Entactiniidae are still a dominant component in Early Triassic time.