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

1. Placodermi的皮甲：皮甲是在日本中部岐阜县Kmitakara-mura的Hukuji发现的。从形态学和组织学研究，推测皮甲为Romudina sp.的棘板，2.古生代软骨鱼类的牙齿：Petalodus allegheniensis的牙齿？Chomatodus sp.和？Janassa sp.，P. a.和中二叠统Sandlodus sp.的化石.中生代板鳃亚纲的牙齿：研究了日本中三叠世的Hybodus sp.、上三叠世的Acrodus sp.和下侏罗世的Asteracanthus sp.的牙齿.第三纪Elasmoblanchii的牙列修复：在富山科学博物馆修复了Carcharocles megalodon的颌骨和牙列。描述了产于斐井县中新世的两颗Isurus牙齿。软骨鱼类牙齿的演化：对化石和现存软骨鱼类牙齿的形态和组织学进行了研究。可以认为，软骨鱼类的牙齿结构并不依赖于它们的进化水平，而是适应它们的饮食习惯的结果。

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.