Taxonomy of Late Silurian to Middle Devonian radiolarians from the Kuzuryu Lake district of the Hida Gaien Belt, Fukui Prefecture, central Japan

摘要

Moderately well-preserved late Late Silurian (Ludlowian to Pridolian) to early Middle Devonian (Eifelian) radiolarians were recovered from clastic rock sequences in the Kuzuryu Lake district of the Hida Gaien Belt, Fukui Prefecture, central Japan. These radiolarians are identical to the faunas of the following four assemblages: Zadrappolus yoshikiensis (Late Silurian; Ludlowian to Pridolian), Pseudospongoprunum sagittatum (latest Silurian; Pridolian), Zadrappolus sp. aff. Z. spinosus (latest Silurian to earliest Devonian; Pridolian to Lochkovian) and Pactarentinia holdsworthi (Early to Middle Devonian; Emsian to Eifelian) Assemblages. These radiolarian faunas from the Hida Gaien Belt are correlative with those of the Kurosegawa Belt (Outer Belt of southwest Japan). Silurian radiolarian faunas from the Hida Gaien and Kurosegawa Belts are similar to those from West Junggar in westernmost China. The Early and Middle Devonian radiolarian faunas in Japan are different from those in eastern Australia in that the Japanese faunas characteristically contain "shelled Palaeoscenidiidae". Thus, based on radiolarian faunal similarity, Silurian and Devonian radiolarian-bearing rock sequences in Japan are inferred to have accumulated in the sea nearer to the Sino-Korean Continent than to eastern Australia in the low latitude of Gondwana. Radiolarians of 26 species belonging to 13 genera were systematically investigated. Ten new species are described: Palaeo-scenidium simplum, Palaeoscenidium hakogasensis, Palaeoscenidium fragilis, Deflantrica furutanii, Pactarentinia intermedia, Pactarentinia igoi, Tlecerina isensis, Ceratoikiscum izumiensis, Palaeopyramidium ramosum and Palaeoumbraculum hidense.