Early Cretaceous nonmarine bivalve assemblages from the Jehol Group in western Liaoning, northeast China

The Jehol Group in western Liaoning yields 13 species of nonmarine bivalves belonging to seven genera. Three assemblages are identified: Arguniella yanshanensis-Sphaerium anderssoni, Margaritifera (Mengyinaia) mengyinensis-Nakamuranaia subrotunda and Arguniella liaoxiensis-Musculiopsis yixianensis, their ages ranging from late Barremian to early Albian. The Arguniella yanshanensis-Sphaerium anderssoni Assemblage is shown to be late Barremian–early Aptian in age on the basis of radiometric dating. The other two assemblages range from middle Aptian to early Albian in age according to both marine intercalations and radiometric dating.