ミャンマー中部の新第三系イラワジ動物相:奇蹄目・偶蹄目

抄録

The upper Neogene Pegu Group and Irrawaddy beds of Central Myanmar yield abundant perissodactyl and artiodactyl (cetartiodactyl) fossils. The upper Pegu or lowest Irrawaddy fauna is correlated with the middle Miocene Chinji fauna of the Siwalik Group, Indo-Pakistan, which contains Brachypotherium, Listriodon, and Microbunodon. The occurrence of Hipparion, Tetraconodon, Bramatherium, and some bovids (e.g., Selenoportax and Pachyportax) represents the early late Miocene fauna in Central Myanmar. Hipparion and Bramatherium disappeared in the latest Miocene or early Pliocene, while the bovids survived until this period. The latest Miocene/early Pliocene fauna is characterized by dominance of bovids and hippos (Hexaprotodon), which indicate the increase of grassland. The late Pliocene fauna is basically not different from the latest Miocene/ early Pliocene fauna because many perissodactyl and artiodactyl species continuously occur from both horizons of the Irrawaddy beds. Through the late Neogene, there were a few times of faunal and floral changes in continental Southeast Asia, and one of the remarkable change was during the late Miocene. Many forest dwellers that existed in the middle Miocene to early late Miocene were probably extinct at least before the latest Miocene when grasslands or open woodlands expanded in Central Myanmar.