Paleontological Study on Dermal Armor, Dermal Tooth and Tooth of Primitive Fishes.

点击翻译按钮获取中文摘要

1. Dermal armor of Placodermi : The dermal armors were discovered from the Hukuji Group (Lower Devonian) in Hukuji, Kmitakara-mura, Gifu Prefecture, central Japan. From the morphological and histological studies, the dermal armor is presumed as spinal plates of Romudina sp., Acanthothoraci.2. Tooth of Paleozoic Chondrichthyes : Teeth of Petalodus allegheniensis, ?Chomatodus sp. and ?Janassa sp. from the Middle Carboniferous, P. a. from the Lower Permian and Sandlodus sp. from the Middle Permian of central Japan were investigated.3. Tooth of Mesozoic Elasmobranchii : Teeth of Hybodus sp. from the Middle Triassic, Acrodus sp. from the Upper Triassic and Asteracanthus sp. from the Lower Jurassic of Japan were investigated.4. Restoration of dentition of Tertiary Elasmoblanchii : The jaws and dentition of Carcharocles megalodon were restored in the Toyama Science Museum. Two teeth of the genus Isurus from the Miocene of Fikui Prefecture were described.5. Evolution of tooth in Chondrichthyes : The morphology and histology of teeth in fossil and extant Chondrichthyes were investigated. It can be considered that the tooth structure of Chondrichthyes is not dependent on their evolutionary levels, but the result of an adaptation to their food habits.