Two types of different realms within Japanese Upper Triassic faunas are recognizable, their ages are discussed. The Kochgatani Fauna is the representative of the Arcto-Pacific realm, its early group is revised to Carnian to Lower Norian in age while its late group is regarded to middle-upper Norian to Rhaetian. The megalodont assemblage and the "St. Cassian" fauna of Japan are both belonging to the Tethyan realm, they may correspond to the relevant faunas of late Camian or early Norian age ofsouth China. The result is significantly for further studying the Chinese nonmarine Upper Triassic sequence.
