Contributors ................................................... vi
Abstract ...................................................... vii
Introduction
Y. Shigeta, T. Komatsu, H.T. Dang, T. Maekawa,
O. Takahashi, G. Tanaka and Y. Tsutsumi ...................... 1
Paleogeographical and geological setting
T. Komatsu, Y. Shigeta and H.T. Dang ......................... 4
Stratigraphy of the Вас Thuy Formation
T. Komatsu, T. Maekawa and Y. Shigeta ........................ 6
Depositional environments of the Вас Thuy Formation
T. Komatsu, T. Maekawa, Y. Shigeta, H.T. Dang and
P.D. Nguyen ................................................ 35
Biostratigraphy
Ammonoid succession
Y. Shigeta .................................................. 47
Conodont succession
T. Maekawa and T. Komatsu ................................... 51
Correlation (Y. Shigeta and T. Maekawa ...................... 54
Age of rhyolite from the Khon Lang Formation
Y. Tsutsumi and T. Komatsu .................................. 54
Discussion
Aspects of Smithian ammonoid fauna
Y. Shigeta .................................................. 57
Internal features in the early whorls of ammonoids
Y. Shigeta and T. Maekawa ................................... 60
Ammonoid mode of occurrence (Y. Shigeta and T. Komatsu ...... 62
Smithian gastropod assemblages of the Вас Thuy Formation
A. Kaim, A. Niitzel and T. Maekawa .......................... 63
Bivalve assemblages and mode of occurrence
T. Komatsu, H.T. Dang and Т.C. Dinh ......................... 64
Brief note on the radiolarian faunas of the Upper Smithian
(Lower Triassic) O. Takahashi ................................ 65
Systematic Paleontology
Cephalopods
Y. Shigeta and H. D. Nguyen ................................. 65
Gastropods
A. Kaim, A. Niitzel and T. Maekawa ......................... 167
Bivalves
T. Komatsu, H.T. Dang and Т.C. Dinh ........................ 184
Conodonts
T. Maekawa and H. Igo ...................................... 190
Ostracods
G. Tanaka, T. Komatsu and T. Maekawa ....................... 271
Radiolarians
O. Takahashi and Y. Miyake ................................. 278
Concluding remarks
Y. Shigeta, T. Komatsu, T. Maekawa and H.T. Dang ........... 294
Acknowledgements .............................................. 295
References .................................................... 295
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