Меловой период

Shigeta Y., Nishimura T., Nifuku K. (in press) Middle and late Maastrichtian (latest Cretaceous) ammonoids from the Akkeshi Bay area, eastern Hokkaido, northern Japan and their biostratigraphic implications // Palaeontological Research, Available online 27 October 2014, doi:10.2517/2014PR034

pdf: http://www.palaeo-soc-japan.jp/download ... _et_al.pdf