Historical distribution patterns of trigonioidids (non-marine Cretaceous bivalves) in Asia and their palaeogeographic significance.

The non-marine trigonioidid bivalves show five phases of radiation in the Cretaceous of Pal-Asia: pre-Aptian (?Valanginian/Hauterivian-Barremian), Aptian, Albian, Cenomanian and Turonian-Maastrichtian. Their distribution patterns show two distinct palaeo-river systems feeding trigonioidids. Before the Cenomanian, the river system occupied the southwestern-southern-southeastern Pal-Asian continental margin areas. During the Turonian-Maastrichtian, it extended along the line of southcentral China-eastern China-northeastern China-northern China and Mongolia-northwestern China-eastern Fergana Basin of Kyrgyzstan-western Tajikistan Basin of Tajikistan-Tashkent area of Kazakhstan-central Kyzylkum of northern Uzbekistan-Aral Sea area of Kazakhstan. Furthermore, the general trigonioidid distribution pattern demonstrates that Japan was probably attached to part of eastern China and/or Korea during the ?Valanginian/Hauterivian-Cenomanian stages.