Recent submarine, geological, and geophysical investigations, including diving surveys, reveal the geological history of the Ryukyu Islands (southern Japan) and the East China Sea. The Ryukyu Arc might have been connected to the Chinese Continent through Taiwan since 2 Ma. The last land-bridge connected to the Asian Continent may have been submerging since 0.02 Ma by both crustal movement and sea level rise from the last Ice Age (Pleistocene). Artificial monuments, which look like stepped pyramids, were discovered beneath the sea off Yonaguni Island, and they are estimated to be ca. 10,000 years ago. It seems to be a principle structure of a large-sized Gusuku, an ancient Okinawan castle. This human-made structure represents compelling evidence suggesting the subsidence processes of the Ryukyu Arc during the Post-Glacaial time.

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 Paleontological and neontological information relevant to the evolutionary and biogeographical history was reviewed for non-volant terrestrial vertebrate taxa of the Ryukyu Archipelago. This is the first step toward an attempt to integrate paleontological and neontological information on these organisms to address problems on the paleogeography of the Ryukyus. Results demonstrated a substantial advantage of such an integrative approach to the inference of past morphological and geographical changes in a few taxa. On the other hand, the present review elucidated a few essential problems in each of the paleontological and neontological fields that require intensive efforts.

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 Ryukyu-ayu in Okinawa Island in the middle of the Ryukyu Archipelago, southern Japan, was examined through a series of ecological survey in order to analyze its morphological and genetic variations from an aquatic resource viewpoint. Here, I describe (1) the history of extinction and reintroduction of Ryukyu-ayu in Okinawa Island, (2) identified problems with the process of reintroduction, and (3) the present condition of wild and reintroduced populations based on genetic analysis.

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