中新世および鮮新世ツタノハガイ属巻貝の新種 : 太平洋地域から絶滅した 1 分岐群

概要

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Three new species of patellogastropod limpets are described, two from the early Middle Miocene Mizunami Group of the Mizunami area and one from the early Pliocene Ochiai Formation of the Tanzawa area, central Japan. These species are Patella mizunamiensis sp. nov., Patella itoigawai sp. nov., and Patella yajimai sp. nov. From an analysis of the shell microstructure, these species can be definitely referred to a clade which ranges from two Late Cretaceous species described from Hokkaido, Japan and Sakhalin, Republic of Russia, to the extant species Patella (Olana) cochlear BORN, 1778,from South African bioprovince. The discovery of these three species from the Miocene and Pliocene of Japan is therefore the first record of the occurrence of this clade, representatives of which are known to have had a paleobiogeographic distribution throughout the northwestern Pacific region during Late Cretaceous and Tertiary times, but which became extinct in this paleobiogeographic province at the beginning of the Pliocene. Preliminary investigations of the Miocene species obtained from this region suggests that the assemblage contains certain elements typical of the present-day faunas inhabiting the tropical and sub-tropical regions of the northwestern Pacific.
1994-06-22