Study of Triassic Tethyan fauna between Japan and U.S.A. -Comparative study between Japan and Pacific coast of U.S.A.

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Tethyan relationships were confirmed by our studies on many bivalves and corals from Sambosan Terrane in Japan as well as from North American exotic terranes. The affinities between Tethyan faunas from Sambosan Terrane and North American exotic terranes, however, was not found here, except for only one conspecifie coral. Two provinces allowed some Tethyan components to move into each province but not close enough to allow some emmigration each other paleogiographycally.The results are stated more precisely as following. Bioclue study (by Tamura) be-longing to the Inner Kochigatani fauna.1. Newton and others (1987) reported several Japanese species from Hells canyon formation Wallowa Mts.. These results were not confirmed by Tamuras comparative study between American and Japanese species. In conclusion no species of Upper Triassic bivalve are co-existent.2. Trigonids have affinities with these of Chinese and Japanese S. E. Asia. This Trigonids assemblage is characterized by Gruenewald, … More Prorotrigonia and Kyushutrigonia (n. gen.) On the other hand American Trigonian province is characterized by Myophori-gonia.Coral study (by Stanley)a) The comparative syoteniative study revealed the prosence of 17 species from Japan as follows.b) Little can be said on paleoecology, since the corals occur in limestone pebbles and clasts of Olistostromal deposits.c) The Japanese corals have a strong Tethyan composition 53% of the species are con-specific with those of the Tethys. Four of these cooccur in South China. There is a high percentage of endemic species (40%) which are not known outside Japan. A small component of the fauna (1%) occurs in Timor.d) Species are a mixture of Carnian and Norian-Rhaetian ages. Most of the Carnian species occur at the Koguchi and Wasabidani localities. Coral from the Mizukami-goe locality is all Norian-Rhaetian species.e) Twenty coral species from the American Wallowa terrane produce percentages similar to Japan : 55% Tethyan species, 40% endemic, and 5% Timor. However there is nearly complete dissimilarity with corals from Japan. Less