Origin and route of the Neogene deep sea molluscan fauna in Ryukyu Islands

研究了冲绳和久米岛地区新近系和第四系地层和古生物学特征。Noda、Kikuchi和Kawagara分别对Yonabaru组和Shinzato组的软体动物、棘刺类和有孔虫进行了古生物学研究，确定了优势区系和特色区系。大部分的深海软体动物从与那巴鲁开始占据主导地位，并在新叠期结束时消失（MacNeiL, 1961, Noda, 1980, 1988, 1991, 1998），就像针孔类动物一样（菊池的研究）。Thatcheria与Teramachia具有相似的生物地理分布。Phanerolepida与Teramachia在太平洋两岸的分布相似，在形态上表现出独特的变异。大部分深海软体动物在“与那原”时期出现，而在“新户”末期消失。川方鉴定了晚中新世至上新世马雅组和阿卡组的底栖有孔虫共112种，其沉积深度在100 ~ 50 m之间有明显的水深变化。

The stratigraphy and paleontology of the Neogene and Quarternary deposits in Okinawa and Kume-jima were examined. According to paleontological studies on the molluscs, echinoids and foraminifers from the Yonabaru and Shinzato Formations by Noda, Kikuchi and Kawagara, repectively, the dominant and characteristic deep sea faunas were recognized. Most of deep sea molluscan faunas become dominant from the Yonabaru and were disappeared at the end of the Shinzato (MacNeiL, 1961, Noda, 1980, 1988, 1991, 1998) as like the echinoid faunas (Kikuchi's research). Thatcheria shows similar biogeographical distribution with that of Teramachia. Phanerolepida shows peculiar morphological variation and shows similar distitribution with that of Teramachia on both sides of the Pacific. Most of deep sea mollsucs had been appeared from the Yonabaru and disappeared at the end of the Shinzato. A total of 112 species of benthic foraminifers from the late Miocene to Pliocene Maja and Aka Formations were identified by Kawagata and show the bathymetric changes from 100 to 50 m in their depositional depth.