Abstract
A moderately well-preserved Llandoverian (early Early Silurian) radiolarian fauna has been discovered from the Ise area of the Hida "Gaien" Belt, in Izumi Village, Fukui Prefecture, central Japan. This is the oldest known radiolarian fauna in Japan, and was recovered from calcareous nodules in the siliceous shale portion of a sedimentary sequence consisting of siliceous shale, alternating tuffaceous sandstone and shale, and tuffaceous sandstone. The fauna contains Haplotaeniatum tegimentum, Syntagentactinia afflicta, S. excelsa, Oriundogutta sp., Inanihella sp., Auliela sp., Palaeoephippium? sp., and Orbiculopylorum sp. This fauna is characterized by an abundance of species in the genera Haplotaeniatum, Syntagentactinia and Oriundogutta, and is comparable with the early to middle Llandoverian Haplotaeniatum tegimentum Assemblage and its equivalents in the southern Urals, Germany, and Nevada. Seventeen species of radiolarians belonging to 12 genera were systematically investigated.
