八重山群島石垣・西表両島の陸産貝類相とその生物地理学的意義

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The Ryukyu Archipelago is located between Kyushu and Formosa and consists of seven groups, namely from north to south, Osumi, Tokara, Amami, Okinawa, Miyako, Yaeyama and Senkaku. The faunas of these groups are more or less different from one another and some biogeographical boundaries were proposed. They are the MIYAKE line between Kyushu and Osumi group, the WATASE line between Osumi and Amami groups, and the HACHISUKA line between Okinawa and Yaeyama groups. The land molluscan fauna of this archipelago originates from that of the central-south part of China with the most remarkable boundary between Osumi and Amami groups. The land molluscan species of Osumi group are mostly in common with those of Kyushu, Shikoku, Honshu and southern Korea, but since they are scarcely in common with those of Amami group, the WATASE line is considered to be a clear boundary. Although Pupinella funatoi, Spirostoma nakadai, Stereophaedusa stereoma, Yakuchloritis albolabris and Satsuma tanegashimae are endemic in the Osumi group, a little faunistic difference is found between Kyushu and Osumi group, and the MIYAKE line dose not seem to be important as the WATASE line. Tokara group is an intermediate area where the land molluscan fauna has many species in common with that of Amami group, whereas a small number of species of Osumi group distribute in the area. Next, between Amami-Okinawa and Miyako-Yaeyama areas there are common genera, but scarcely common species. Therefore, the HACHISUKA line is a significant boundary in land molluscan fauna. Between Amami and Okinawa groups, the former has the genera such as Pupinella, Trichelix, Chamalycaeus which are not distributed in the latter and some species specialize to subspecies in each group. Between Miyako and Yaeyama groups the difference of the land molluscan fauna is small. On the other hand, these two groups have the species such as Aegiste nackensii, A. osbeckii and Cyclotus taivanus in common with Formosa. The land molluscs such as Coniglobus tadai, Buliminopsis takarai and Tyrannozaptyx takarai from Senkaku group are similar to those species of Yaeyama group, excepting the species of the genus Nesiohelix, N. solida which shows close relationship of Senkaku group to Formosa and Continent of China. In Ishigaki and Iriomote Islands of Yaeyama group 45 species of land molluscs were collected, among which 16 species including a new species and 3 subspecies are endemic. The new species, Enteroplax yaeyamensis, of the family Strobilopsidae described herewith is the Philippine element.
国立科学博物館の論文
1974-09-20

八重山群島石垣・西表両島の陸産貝類相とその生物地理学的意義

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