Bulletin of the Mizunami Fossil Museum

Monograph of the Mizunami Fossil Museum No. 6

The history of studies of Fortipectininae Masuda, 1963 and Patinopectininae Habe, 1977, the size and composition of the subfamilies and their systematic relationships are considered. It is concluded that Fortipectininae is a typical group of near-Asian Pacific origin, and it has been in North Japan-Sakhalin Paleogene province in the Late Oligocene. Some members of this subfamily - species of the genera Mizuhopecten and Fortipecten migrated to the American coast of the North Pacific in the Late Miocene and Early Pliocene. The Patinopectininae is a group of Neogene genesis, forming and further evolution of this group are wholly connected with the Pacific coast of North America.

Patinoρecten has never spread to the North-West Pacific. An analysis of phylogenetical and geochronological relationships of the two subfamilies gives an additional and quite important argumnent for regarding the Mizuhopecten (Fortipectininae) and the Patinopecten (Patinopectininae) as two separate genera with independent phylogenetic development.