2009 Fiscal Year Final Research Report

Diversification events of marine, brackish and freshwater bivalves in the Early Cretaceous

Research Project

Project/Area Number	19540495
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Stratigraphy/Paleontology
Research Institution	Kochi University
Principal Investigator	KONDO Yasuo Kochi University, 教育研究部自然科学系, 教授 (90192583)
Co-Investigator(Kenkyū-buntansha)	KOZAI Takeshi 鳴門教育大学, 学校教育学部, 教授 (50314886)
Research Collaborator	KIKUCHI Naoki
Project Period (FY)	2007 – 2009
Keywords	二枚貝 / 塩分耐性 / 白亜紀 / 白亜系 / 日本 / 中国
Research Abstract	Early Cretaceous bivalves were analyzed for specimens from Japan and related part of China. Marine, brackish and freshwater bivalves displayed different pattern of dispersion and diversification. Taxonomic analysis of the genus Nippononaia has shown that the emergence and diversification of the Early Cretaceous species are the result of corridor-like waterway formed by the displacement of lateral faults in the eastern part of the Yanze and Sino-Korea blocks. Marine bivalves, on the other hand, were influenced by global environmental changes. In contrast to these stenohaline habitats, estuaries were colonized by euryhaline bivalves. Tetorla sanchuensls, one of the early heterodont bivalves having long siphons, was found to have inhabited in the nnermost part of estuary.